Classical conditioning

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Classical conditioning (also known as Pavlovian or respondent conditioning) is a behavioral procedure in which a biologically potent stimulus (e.g. food) is paired with a previously neutral stimulus (e.g. a triangle). It also refers to the learning process that results from this pairing, through which the neutral stimulus comes to elicit a response (e.g. salivation) that is usually similar to the one elicited by the potent stimulus.

Classical conditioning is distinct from operant conditioning (also called instrumental conditioning), through which the strength of a voluntary behavior is modified by reinforcement or punishment. However, classical conditioning can affect operant conditioning in various ways; notably, classically conditioned stimuli may serve to reinforce operant responses.

Classical conditioning was first studied in detail by Ivan Pavlov, who conducted experiments with dogs and published his findings in 1897. During the Russian physiologist's study of digestion, Pavlov observed that the dogs serving as his subjects drooled when they were being served meat.

Classical conditioning is a basic behavioral mechanism, and its neural substrates are now beginning to be understood. Though it is sometimes hard to distinguish classical conditioning from other forms of associative learning (e.g. instrumental learning and human associative memory), a number of observations differentiate them, especially the contingencies whereby learning occurs.

Together with operant conditioning, classical conditioning became the foundation of behaviorism, a school of psychology which was dominant in the mid-20th century and is still an important influence on the practice of psychological therapy and the study of animal behavior. Classical conditioning has been applied in other areas as well. For example, it may affect the body's response to psychoactive drugs, the regulation of hunger, research on the neural basis of learning and memory, and in certain social phenomena such as the false consensus effect.

Definition

Classical conditioning occurs when a conditioned stimulus (CS) is paired with an unconditioned stimulus (US). Usually, the conditioned stimulus is a neutral stimulus (e.g., the sound of a tuning fork), the unconditioned stimulus is biologically potent (e.g., the taste of food) and the unconditioned response (UR) to the unconditioned stimulus is an unlearned reflex response (e.g., salivation). After pairing is repeated the organism exhibits a conditioned response (CR) to the conditioned stimulus when the conditioned stimulus is presented alone. (A conditioned response may occur after only one pairing.) Thus, unlike the UR, the CR is acquired through experience, and it is also less permanent than the UR.

Usually the conditioned response is similar to the unconditioned response, but sometimes it is quite different. For this and other reasons, most learning theorists suggest that the conditioned stimulus comes to signal or predict the unconditioned stimulus, and go on to analyze the consequences of this signal. Robert A. Rescorla provided a clear summary of this change in thinking, and its implications, in his 1988 article "Pavlovian conditioning: It's not what you think it is". Despite its widespread acceptance, Rescorla's thesis may not be defensible.

Classical conditioning differs from operant or instrumental conditioning: in classical conditioning, behaviors are modified through the association of stimuli as described above, whereas in operant conditioning behaviors are modified by the effect they produce (i.e., reward or punishment).

Procedures

Ivan Pavlov research on dog's reflex setup

Pavlov's research

The best-known and most thorough early work on classical conditioning was done by Ivan Pavlov, although Edwin Twitmyer published some related findings a year earlier. During his research on the physiology of digestion in dogs, Pavlov developed a procedure that enabled him to study the digestive processes of animals over long periods of time. He redirected the animal's digestive fluids outside the body, where they could be measured. Pavlov noticed that his dogs began to salivate in the presence of the technician who normally fed them, rather than simply salivating in the presence of food. Pavlov called the dogs' anticipatory salivation "psychic secretion". Putting these informal observations to an experimental test, Pavlov presented a stimulus (e.g. the sound of a metronome) and then gave the dog food; after a few repetitions, the dogs started to salivate in response to the stimulus. Pavlov concluded that if a particular stimulus in the dog's surroundings was present when the dog was given food then that stimulus could become associated with food and cause salivation on its own.

Classical Conditioning Diagram

Terminology

In Pavlov's experiments the unconditioned stimulus (US) was the food because its effects did not depend on previous experience. The metronome's sound is originally a neutral stimulus (NS) because it does not elicit salivation in the dogs. After conditioning, the metronome's sound becomes the conditioned stimulus (CS) or conditional stimulus; because its effects depend on its association with food. Likewise, the responses of the dog follow the same conditioned-versus-unconditioned arrangement. The conditioned response (CR) is the response to the conditioned stimulus, whereas the unconditioned response (UR) corresponds to the unconditioned stimulus.

Pavlov reported many basic facts about conditioning; for example, he found that learning occurred most rapidly when the interval between the CS and the appearance of the US was relatively short.

As noted earlier, it is often thought that the conditioned response is a replica of the unconditioned response, but Pavlov noted that saliva produced by the CS differs in composition from that produced by the US. In fact, the CR may be any new response to the previously neutral CS that can be clearly linked to experience with the conditional relationship of CS and US. It was also thought that repeated pairings are necessary for conditioning to emerge, but many CRs can be learned with a single trial, especially in fear conditioning and taste aversion learning.

Diagram representing forward conditioning. The time interval increases from left to right.

Forward conditioning

Learning is fastest in forward conditioning. During forward conditioning, the onset of the CS precedes the onset of the US in order to signal that the US will follow. Two common forms of forward conditioning are delay and trace conditioning.

• Delay conditioning: In delay conditioning, the CS is presented and is overlapped by the presentation of the US. For example, if a person hears a buzzer for five seconds, during which time air is puffed into their eye, the person will blink. After several pairings of the buzzer and the puff, the person will blink at the sound of the buzzer alone. This is delay conditioning.
• Trace conditioning: During trace conditioning, the CS and US do not overlap. Instead, the CS begins and ends before the US is presented. The stimulus-free period is called the trace interval or the conditioning interval. If in the above buzzer example, the puff came a second after the sound of the buzzer stopped, that would be trace conditioning, with a trace or conditioning interval of one second.

Simultaneous conditioning

Classical conditioning procedures and effects

During simultaneous conditioning, the CS and US are presented and terminated at the same time. For example: If a person hears a bell and has air puffed into their eye at the same time, and repeated pairings like this led to the person blinking when they hear the bell despite the puff of air being absent, this demonstrates that simultaneous conditioning has occurred.

Second-order and higher-order conditioning

Main article: Second-order conditioning

Second-order or higher-order conditioning follow a two-step procedure. First a neutral stimulus ("CS1") comes to signal a US through forward conditioning. Then a second neutral stimulus ("CS2") is paired with the first (CS1) and comes to yield its own conditioned response. For example: A bell might be paired with food until the bell elicits salivation. If a light is then paired with the bell, then the light may come to elicit salivation as well. The bell is the CS1 and the food is the US. The light becomes the CS2 once it is paired with the CS1.

Backward conditioning

Backward conditioning occurs when a CS immediately follows a US. Unlike the usual conditioning procedure, in which the CS precedes the US, the conditioned response given to the CS tends to be inhibitory. This presumably happens because the CS serves as a signal that the US has ended, rather than as a signal that the US is about to appear. For example, a puff of air directed at a person's eye could be followed by the sound of a buzzer.

Temporal conditioning

In temporal conditioning, a US is presented at regular intervals, for instance every 10 minutes. Conditioning is said to have occurred when the CR tends to occur shortly before each US. This suggests that animals have a biological clock that can serve as a CS. This method has also been used to study timing ability in animals (see Animal cognition).

The example below shows the temporal conditioning, as US such as food to a hungry mouse is simply delivered on a regular time schedule such as every thirty seconds. After sufficient exposure the mouse will begin to salivate just before the food delivery. This then makes it temporal conditioning as it would appear that the mouse is conditioned to the passage of time.

Zero contingency procedure

In this procedure, the CS is paired with the US, but the US also occurs at other times. If this occurs, it is predicted that the US is likely to happen in the absence of the CS. In other words, the CS does not "predict" the US. In this case, conditioning fails and the CS does not come to elicit a CR. This finding – that prediction rather than CS-US pairing is the key to conditioning – greatly influenced subsequent conditioning research and theory.

Extinction

Main article: Extinction (psychology)

In the extinction procedure, the CS is presented repeatedly in the absence of a US. This is done after a CS has been conditioned by one of the methods above. When this is done, the CR frequency eventually returns to pre-training levels. However, extinction does not eliminate the effects of the prior conditioning. This is demonstrated by spontaneous recovery – when there is a sudden appearance of the (CR) after extinction occurs – and other related phenomena (see "Recovery from extinction" below). These phenomena can be explained by postulating accumulation of inhibition when a weak stimulus is presented.

Phenomena observed

Acquisition

During acquisition, the CS and US are paired as described above. The extent of conditioning may be tracked by test trials. In these test trials, the CS is presented alone and the CR is measured. A single CS-US pairing may suffice to yield a CR on a test, but usually a number of pairings are necessary and there is a gradual increase in the conditioned response to the CS. This repeated number of trials increase the strength and/or frequency of the CR gradually. The speed of conditioning depends on a number of factors, such as the nature and strength of both the CS and the US, previous experience and the animal's motivational state. The process slows down as it nears completion.

Extinction

If the CS is presented without the US, and this process is repeated often enough, the CS will eventually stop eliciting a CR. At this point the CR is said to be "extinguished."

External inhibition

External inhibition may be observed if a strong or unfamiliar stimulus is presented just before, or at the same time as, the CS. This causes a reduction in the conditioned response to the CS.

Recovery from extinction

Several procedures lead to the recovery of a CR that had been first conditioned and then extinguished. This illustrates that the extinction procedure does not eliminate the effect of conditioning. These procedures are the following:

• Reacquisition: If the CS is again paired with the US, a CR is again acquired, but this second acquisition usually happens much faster than the first one.
• Spontaneous recovery: Spontaneous recovery is defined as the reappearance of a previously extinguished conditioned response after a rest period. That is, if the CS is tested at a later time (for example an hour or a day) after extinction it will again elicit a CR. This renewed CR is usually much weaker than the CR observed prior to extinction.
• Disinhibition: If the CS is tested just after extinction and an intense but associatively neutral stimulus has occurred, there may be a temporary recovery of the conditioned response to the CS.
• Reinstatement: If the US used in conditioning is presented to a subject in the same place where conditioning and extinction occurred, but without the CS being present, the CS often elicits a response when it is tested later.
• Renewal: Renewal is a reemergence of a conditioned response following extinction when an animal is returned to the environment *(or similar environment) in which the conditioned response was acquired.

Stimulus generalization

Stimulus generalization is said to occur if, after a particular CS has come to elicit a CR, a similar test stimulus is found to elicit the same CR. Usually the more similar the test stimulus is to the CS the stronger the CR will be to the test stimulus. Conversely, the more the test stimulus differs from the CS, the weaker the CR will be, or the more it will differ from that previously observed.

Stimulus discrimination

One observes stimulus discrimination when one stimulus ("CS1") elicits one CR and another stimulus ("CS2") elicits either another CR or no CR at all. This can be brought about by, for example, pairing CS1 with an effective US and presenting CS2 with no US.

Latent inhibition

Main article: Latent inhibition

Latent inhibition refers to the observation that it takes longer for a familiar stimulus to become a CS than it does for a novel stimulus to become a CS, when the stimulus is paired with an effective US.

Conditioned suppression

This is one of the most common ways to measure the strength of learning in classical conditioning. A typical example of this procedure is as follows: a rat first learns to press a lever through operant conditioning. Then, in a series of trials, the rat is exposed to a CS, a light or a noise, followed by the US, a mild electric shock. An association between the CS and US develops, and the rat slows or stops its lever pressing when the CS comes on. The rate of pressing during the CS measures the strength of classical conditioning; that is, the slower the rat presses, the stronger the association of the CS and the US. (Slow pressing indicates a "fear" conditioned response, and it is an example of a conditioned emotional response; see section below.)

Conditioned inhibition

Typically, three phases of conditioning are used.

Phase 1

A CS (CS+) is paired with a US until asymptotic CR levels are reached.

Phase 2

CS+/US trials are continued, but these are interspersed with trials on which the CS+ is paired with a second CS, (the CS-) but not with the US (i.e. CS+/CS- trials). Typically, organisms show CRs on CS+/US trials, but stop responding on CS+/CS− trials.

Phase 3

• Summation test for conditioned inhibition: The CS- from phase 2 is presented together with a new CS+ that was conditioned as in phase 1. Conditioned inhibition is found if the response is less to the CS+/CS- pair than it is to the CS+ alone.
• Retardation test for conditioned inhibition: The CS- from phase 2 is paired with the US. If conditioned inhibition has occurred, the rate of acquisition to the previous CS− should be less than the rate of acquisition that would be found without the phase 2 treatment.

Blocking

Main article: Blocking effect

This form of classical conditioning involves two phases.

Phase 1

A CS (CS1) is paired with a US.

Phase 2

A compound CS (CS1+CS2) is paired with a US.

Test

A separate test for each CS (CS1 and CS2) is performed. The blocking effect is observed in a lack of conditional response to CS2, suggesting that the first phase of training blocked the acquisition of the second CS.

Theories

Data sources

Experiments on theoretical issues in conditioning have mostly been done on vertebrates, especially rats and pigeons. However, conditioning has also been studied in invertebrates, and very important data on the neural basis of conditioning has come from experiments on the sea slug, Aplysia. Most relevant experiments have used the classical conditioning procedure, although instrumental (operant) conditioning experiments have also been used, and the strength of classical conditioning is often measured through its operant effects, as in conditioned suppression (see Phenomena section above) and autoshaping.

Stimulus-substitution theory

Further information: Counterconditioning

According to Pavlov, conditioning does not involve the acquisition of any new behavior, but rather the tendency to respond in old ways to new stimuli. Thus, he theorized that the CS merely substitutes for the US in evoking the reflex response. This explanation is called the stimulus-substitution theory of conditioning. A critical problem with the stimulus-substitution theory is that the CR and UR are not always the same. Pavlov himself observed that a dog's saliva produced as a CR differed in composition from that produced as a UR. The CR is sometimes even the opposite of the UR. For example: the unconditional response to electric shock is an increase in heart rate, whereas a CS that has been paired with the electric shock elicits a decrease in heart rate. (However, it has been proposed that only when the UR does not involve the central nervous system are the CR and the UR opposites.)

Rescorla–Wagner model

Main article: Rescorla–Wagner model

The Rescorla–Wagner (R–W) model is a relatively simple yet powerful model of conditioning. The model predicts a number of important phenomena, but it also fails in important ways, thus leading to a number of modifications and alternative models. However, because much of the theoretical research on conditioning in the past 40 years has been instigated by this model or reactions to it, the R–W model deserves a brief description here.

The Rescorla-Wagner model argues that there is a limit to the amount of conditioning that can occur in the pairing of two stimuli. One determinant of this limit is the nature of the US. For example: pairing a bell with a juicy steak is more likely to produce salivation than pairing the bell with a piece of dry bread, and dry bread is likely to work better than a piece of cardboard. A key idea behind the R–W model is that a CS signals or predicts the US. One might say that before conditioning, the subject is surprised by the US. However, after conditioning, the subject is no longer surprised, because the CS predicts the coming of the US. (Note that the model can be described mathematically and that words like predict, surprise, and expect are only used to help explain the model.) Here the workings of the model are illustrated with brief accounts of acquisition, extinction, and blocking. The model also predicts a number of other phenomena, see main article on the model.

Equation

$${\displaystyle \mathrm{\Delta }V=\alpha \beta (\lambda -\mathrm{\Sigma }V)}$$

This is the Rescorla-Wagner equation. It specifies the amount of learning that will occur on a single pairing of a conditioning stimulus (CS) with an unconditioned stimulus (US). The above equation is solved repeatedly to predict the course of learning over many such trials.

In this model the degree of learning is measured by how well the CS predicts the US, which is given by the "associative strength" of the CS. In the equation, V represents the current associative strength of the CS, and ∆V is the change in this strength that happens on a given trial. ΣV is the sum of the strengths of all stimuli present in the situation. λ is the maximum associative strength that a given US will support; its value is usually set to 1 on trials when the US is present, and 0 when the US is absent. α and β are constants related to the salience of the CS and the speed of learning for a given US. How the equation predicts various experimental results is explained in following sections. For further details, see the main article on the model.

R–W model: acquisition

The R–W model measures conditioning by assigning an "associative strength" to the CS and other local stimuli. Before a CS is conditioned it has an associative strength of zero. Pairing the CS and the US causes a gradual increase in the associative strength of the CS. This increase is determined by the nature of the US (e.g. its intensity). The amount of learning that happens during any single CS-US pairing depends on the difference between the total associative strengths of CS and other stimuli present in the situation (ΣV in the equation), and a maximum set by the US (λ in the equation). On the first pairing of the CS and US, this difference is large and the associative strength of the CS takes a big step up. As CS-US pairings accumulate, the US becomes more predictable, and the increase in associative strength on each trial becomes smaller and smaller. Finally, the difference between the associative strength of the CS (plus any that may accrue to other stimuli) and the maximum strength reaches zero. That is, the US is fully predicted, the associative strength of the CS stops growing, and conditioning is complete.

R–W model: extinction

Comparing the associate strength by R-W model in Learning

The associative process described by the R–W model also accounts for extinction (see "procedures" above). The extinction procedure starts with a positive associative strength of the CS, which means that the CS predicts that the US will occur. On an extinction trial the US fails to occur after the CS. As a result of this "surprising" outcome, the associative strength of the CS takes a step down. Extinction is complete when the strength of the CS reaches zero; no US is predicted, and no US occurs. However, if that same CS is presented without the US but accompanied by a well-established conditioned inhibitor (CI), that is, a stimulus that predicts the absence of a US (in R-W terms, a stimulus with a negative associate strength) then R-W predicts that the CS will not undergo extinction (its V will not decrease in size).

R–W model: blocking

Main article: Blocking effect

The most important and novel contribution of the R–W model is its assumption that the conditioning of a CS depends not just on that CS alone, and its relationship to the US, but also on all other stimuli present in the conditioning situation. In particular, the model states that the US is predicted by the sum of the associative strengths of all stimuli present in the conditioning situation. Learning is controlled by the difference between this total associative strength and the strength supported by the US. When this sum of strengths reaches a maximum set by the US, conditioning ends as just described.

The R–W explanation of the blocking phenomenon illustrates one consequence of the assumption just stated. In blocking (see "phenomena" above), CS1 is paired with a US until conditioning is complete. Then on additional conditioning trials a second stimulus (CS2) appears together with CS1, and both are followed by the US. Finally CS2 is tested and shown to produce no response because learning about CS2 was "blocked" by the initial learning about CS1. The R–W model explains this by saying that after the initial conditioning, CS1 fully predicts the US. Since there is no difference between what is predicted and what happens, no new learning happens on the additional trials with CS1+CS2, hence CS2 later yields no response.

Theoretical issues and alternatives to the Rescorla–Wagner model

One of the main reasons for the importance of the R–W model is that it is relatively simple and makes clear predictions. Tests of these predictions have led to a number of important new findings and a considerably increased understanding of conditioning. Some new information has supported the theory, but much has not, and it is generally agreed that the theory is, at best, too simple. However, no single model seems to account for all the phenomena that experiments have produced. Following are brief summaries of some related theoretical issues.

Content of learning

The R–W model reduces conditioning to the association of a CS and US, and measures this with a single number, the associative strength of the CS. A number of experimental findings indicate that more is learned than this. Among these are two phenomena described earlier in this article

• Latent inhibition: If a subject is repeatedly exposed to the CS before conditioning starts, then conditioning takes longer. The R–W model cannot explain this because preexposure leaves the strength of the CS unchanged at zero.
• Recovery of responding after extinction: It appears that something remains after extinction has reduced associative strength to zero because several procedures cause responding to reappear without further conditioning.

Role of attention in learning

Latent inhibition might happen because a subject stops focusing on a CS that is seen frequently before it is paired with a US. In fact, changes in attention to the CS are at the heart of two prominent theories that try to cope with experimental results that give the R–W model difficulty. In one of these, proposed by Nicholas Mackintosh, the speed of conditioning depends on the amount of attention devoted to the CS, and this amount of attention depends in turn on how well the CS predicts the US. Pearce and Hall proposed a related model based on a different attentional principle Both models have been extensively tested, and neither explains all the experimental results. Consequently, various authors have attempted hybrid models that combine the two attentional processes. Pearce and Hall in 2010 integrated their attentional ideas and even suggested the possibility of incorporating the Rescorla-Wagner equation into an integrated model.

Context

As stated earlier, a key idea in conditioning is that the CS signals or predicts the US (see "zero contingency procedure" above). However, for example, the room in which conditioning takes place also "predicts" that the US may occur. Still, the room predicts with much less certainty than does the experimental CS itself, because the room is also there between experimental trials, when the US is absent. The role of such context is illustrated by the fact that the dogs in Pavlov's experiment would sometimes start salivating as they approached the experimental apparatus, before they saw or heard any CS. Such so-called "context" stimuli are always present, and their influence helps to account for some otherwise puzzling experimental findings. The associative strength of context stimuli can be entered into the Rescorla-Wagner equation, and they play an important role in the comparator and computational theories outlined below.

Comparator theory

To find out what has been learned, we must somehow measure behavior ("performance") in a test situation. However, as students know all too well, performance in a test situation is not always a good measure of what has been learned. As for conditioning, there is evidence that subjects in a blocking experiment do learn something about the "blocked" CS, but fail to show this learning because of the way that they are usually tested.

"Comparator" theories of conditioning are "performance based", that is, they stress what is going on at the time of the test. In particular, they look at all the stimuli that are present during testing and at how the associations acquired by these stimuli may interact. To oversimplify somewhat, comparator theories assume that during conditioning the subject acquires both CS-US and context-US associations. At the time of the test, these associations are compared, and a response to the CS occurs only if the CS-US association is stronger than the context-US association. After a CS and US are repeatedly paired in simple acquisition, the CS-US association is strong and the context-US association is relatively weak. This means that the CS elicits a strong CR. In "zero contingency" (see above), the conditioned response is weak or absent because the context-US association is about as strong as the CS-US association. Blocking and other more subtle phenomena can also be explained by comparator theories, though, again, they cannot explain everything.

Computational theory

An organism's need to predict future events is central to modern theories of conditioning. Most theories use associations between stimuli to take care of these predictions. For example: In the R–W model, the associative strength of a CS tells us how strongly that CS predicts a US. A different approach to prediction is suggested by models such as that proposed by Gallistel & Gibbon (2000, 2002). Here the response is not determined by associative strengths. Instead, the organism records the times of onset and offset of CSs and USs and uses these to calculate the probability that the US will follow the CS. A number of experiments have shown that humans and animals can learn to time events (see Animal cognition), and the Gallistel & Gibbon model yields very good quantitative fits to a variety of experimental data. However, recent studies have suggested that duration-based models cannot account for some empirical findings as well as associative models.

Element-based models

The Rescorla-Wagner model treats a stimulus as a single entity, and it represents the associative strength of a stimulus with one number, with no record of how that number was reached. As noted above, this makes it hard for the model to account for a number of experimental results. More flexibility is provided by assuming that a stimulus is internally represented by a collection of elements, each of which may change from one associative state to another. For example, the similarity of one stimulus to another may be represented by saying that the two stimuli share elements in common. These shared elements help to account for stimulus generalization and other phenomena that may depend upon generalization. Also, different elements within the same set may have different associations, and their activations and associations may change at different times and at different rates. This allows element-based models to handle some otherwise inexplicable results.

The SOP model

A prominent example of the element approach is the "SOP" model of Wagner. The model has been elaborated in various ways since its introduction, and it can now account in principle for a very wide variety of experimental findings. The model represents any given stimulus with a large collection of elements. The time of presentation of various stimuli, the state of their elements, and the interactions between the elements, all determine the course of associative processes and the behaviors observed during conditioning experiments.

The SOP account of simple conditioning exemplifies some essentials of the SOP model. To begin with, the model assumes that the CS and US are each represented by a large group of elements. Each of these stimulus elements can be in one of three states:

• primary activity (A1) - Roughly speaking, the stimulus is "attended to." (References to "attention" are intended only to aid understanding and are not part of the model.)
• secondary activity (A2) - The stimulus is "peripherally attended to."
• inactive (I) – The stimulus is "not attended to."

Of the elements that represent a single stimulus at a given moment, some may be in state A1, some in state A2, and some in state I.

When a stimulus first appears, some of its elements jump from inactivity I to primary activity A1. From the A1 state they gradually decay to A2, and finally back to I. Element activity can only change in this way; in particular, elements in A2 cannot go directly back to A1. If the elements of both the CS and the US are in the A1 state at the same time, an association is learned between the two stimuli. This means that if, at a later time, the CS is presented ahead of the US, and some CS elements enter A1, these elements will activate some US elements. However, US elements activated indirectly in this way only get boosted to the A2 state. (This can be thought of the CS arousing a memory of the US, which will not be as strong as the real thing.) With repeated CS-US trials, more and more elements are associated, and more and more US elements go to A2 when the CS comes on. This gradually leaves fewer and fewer US elements that can enter A1 when the US itself appears. In consequence, learning slows down and approaches a limit. One might say that the US is "fully predicted" or "not surprising" because almost all of its elements can only enter A2 when the CS comes on, leaving few to form new associations.

The model can explain the findings that are accounted for by the Rescorla-Wagner model and a number of additional findings as well. For example, unlike most other models, SOP takes time into account. The rise and decay of element activation enables the model to explain time-dependent effects such as the fact that conditioning is strongest when the CS comes just before the US, and that when the CS comes after the US ("backward conditioning") the result is often an inhibitory CS. Many other more subtle phenomena are explained as well.

A number of other powerful models have appeared in recent years which incorporate element representations. These often include the assumption that associations involve a network of connections between "nodes" that represent stimuli, responses, and perhaps one or more "hidden" layers of intermediate interconnections. Such models make contact with a current explosion of research on neural networks, artificial intelligence and machine learning.

Applications

Neural basis of learning and memory

Pavlov proposed that conditioning involved a connection between brain centers for conditioned and unconditioned stimuli. His physiological account of conditioning has been abandoned, but classical conditioning continues to be used to study the neural structures and functions that underlie learning and memory. Forms of classical conditioning that are used for this purpose include, among others, fear conditioning, eyeblink conditioning, and the foot contraction conditioning of Hermissenda crassicornis, a sea-slug. Both fear and eyeblink conditioning involve a neutral stimulus, frequently a tone, becoming paired with an unconditioned stimulus. In the case of eyeblink conditioning, the US is an air-puff, while in fear conditioning the US is threatening or aversive such as a foot shock.

"Available data demonstrate that discrete regions of the cerebellum and associated brainstem areas contain neurons that alter their activity during conditioning – these regions are critical for the acquisition and performance of this simple learning task. It appears that other regions of the brain, including the hippocampus, amygdala, and prefrontal cortex, contribute to the conditioning process, especially when the demands of the task get more complex."

Fear and eyeblink conditioning involve generally non overlapping neural circuitry, but share molecular mechanisms. Fear conditioning occurs in the basolateral amygdala, which receives glutaminergic input directly from thalamic afferents, as well as indirectly from prefrontal projections. The direct projections are sufficient for delay conditioning, but in the case of trace conditioning, where the CS needs to be internally represented despite a lack of external stimulus, indirect pathways are necessary. The anterior cingulate is one candidate for intermediate trace conditioning, but the hippocampus may also play a major role. Presynaptic activation of protein kinase A and postsynaptic activation of NMDA receptors and its signal transduction pathway are necessary for conditioning related plasticity. CREB is also necessary for conditioning related plasticity, and it may induce downstream synthesis of proteins necessary for this to occur. As NMDA receptors are only activated after an increase in presynaptic calcium(thereby releasing the Mg2+ block), they are a potential coincidence detector that could mediate spike timing dependent plasticity. STDP constrains LTP to situations where the CS predicts the US, and LTD to the reverse.

Behavioral therapies

Main article: Behavior therapy

Some therapies associated with classical conditioning are aversion therapy, systematic desensitization and flooding. Aversion therapy is a type of behavior therapy designed to make patients cease an undesirable habit by associating the habit with a strong unpleasant unconditioned stimulus. For example, a medication might be used to associate the taste of alcohol with stomach upset. Systematic desensitization is a treatment for phobias in which the patient is trained to relax while being exposed to progressively more anxiety-provoking stimuli (e.g. angry words). This is an example of counterconditioning, intended to associate the feared stimuli with a response (relaxation) that is incompatible with anxiety. Flooding is a form of desensitization that attempts to eliminate phobias and anxieties by repeated exposure to highly distressing stimuli until the lack of reinforcement of the anxiety response causes its extinction. "Flooding" usually involves actual exposure to the stimuli, whereas the term "implosion" refers to imagined exposure, but the two terms are sometimes used synonymously.

Conditioning therapies usually take less time than humanistic therapies.

Conditioned drug response

A stimulus that is present when a drug is administered or consumed may eventually evoke a conditioned physiological response that mimics the effect of the drug. This is sometimes the case with caffeine; habitual coffee drinkers may find that the smell of coffee gives them a feeling of alertness. In other cases, the conditioned response is a compensatory reaction that tends to offset the effects of the drug. For example, if a drug causes the body to become less sensitive to pain, the compensatory conditioned reaction may be one that makes the user more sensitive to pain. This compensatory reaction may contribute to drug tolerance. If so, a drug user may increase the amount of drug consumed in order to feel its effects, and end up taking very large amounts of the drug. In this case a dangerous overdose reaction may occur if the CS happens to be absent, so that the conditioned compensatory effect fails to occur. For example, if the drug has always been administered in the same room, the stimuli provided by that room may produce a conditioned compensatory effect; then an overdose reaction may happen if the drug is administered in a different location where the conditioned stimuli are absent.

Conditioned hunger

Signals that consistently precede food intake can become conditioned stimuli for a set of bodily responses that prepares the body for food and digestion. These reflexive responses include the secretion of digestive juices into the stomach and the secretion of certain hormones into the blood stream, and they induce a state of hunger. An example of conditioned hunger is the "appetizer effect." Any signal that consistently precedes a meal, such as a clock indicating that it is time for dinner, can cause people to feel hungrier than before the signal. The lateral hypothalamus (LH) is involved in the initiation of eating. The nigrostriatal pathway, which includes the substantia nigra, the lateral hypothalamus, and the basal ganglia have been shown to be involved in hunger motivation.

Conditioned emotional response

Further information: Conditioned emotional response and Fear conditioning

The influence of classical conditioning can be seen in emotional responses such as phobia, disgust, nausea, anger, and sexual arousal. A familiar example is conditioned nausea, in which the CS is the sight or smell of a particular food that in the past has resulted in an unconditioned stomach upset. Similarly, when the CS is the sight of a dog and the US is the pain of being bitten, the result may be a conditioned fear of dogs. An example of conditioned emotional response is conditioned suppression.

As an adaptive mechanism, emotional conditioning helps shield an individual from harm or prepare it for important biological events such as sexual activity. Thus, a stimulus that has occurred before sexual interaction comes to cause sexual arousal, which prepares the individual for sexual contact. For example, sexual arousal has been conditioned in human subjects by pairing a stimulus like a picture of a jar of pennies with views of an erotic film clip. Similar experiments involving blue gourami fish and domesticated quail have shown that such conditioning can increase the number of offspring. These results suggest that conditioning techniques might help to increase fertility rates in infertile individuals and endangered species.

Pavlovian-instrumental transfer

Main article: Pavlovian-instrumental transfer

Pavlovian-instrumental transfer is a phenomenon that occurs when a conditioned stimulus (CS, also known as a "cue") that has been associated with rewarding or aversive stimuli via classical conditioning alters motivational salience and operant behavior. In a typical experiment, a rat is presented with sound-food pairings (classical conditioning). Separately, the rat learns to press a lever to get food (operant conditioning). Test sessions now show that the rat presses the lever faster in the presence of the sound than in silence, although the sound has never been associated with lever pressing.

Pavlovian-instrumental transfer is suggested to play a role in the differential outcomes effect, a procedure which enhances operant discrimination by pairing stimuli with specific outcomes.

Personality psychology

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Personality_psychology 

Personality psychology is a branch of psychology that examines personality and its variation among individuals. It aims to show how people are individually different due to psychological forces. Its areas of focus include:

• construction of a coherent picture of the individual and their major psychological processes
• investigation of individual psychological differences
• investigation of human nature and psychological similarities between individuals

"Personality" is a dynamic and organized set of characteristics possessed by an individual that uniquely influences their environment, cognition, emotions, motivations, and behaviors in various situations. The word personality originates from the Latin persona, which means "mask".

Personality also pertains to the pattern of thoughts, feelings, social adjustments, and behaviors persistently exhibited over time that strongly influences one's expectations, self-perceptions, values, and attitudes. Personality also predicts human reactions to other people, problems, and stress. Gordon Allport (1937) described two major ways to study personality: the nomothetic and the idiographic. Nomothetic psychology seeks general laws that can be applied to many different people, such as the principle of self-actualization or the trait of extraversion. Idiographic psychology is an attempt to understand the unique aspects of a particular individual.

The study of personality has a broad and varied history in psychology, with an abundance of theoretical traditions. The major theories include dispositional (trait) perspective, psychodynamic, humanistic, biological, behaviorist, evolutionary, and social learning perspective. Many researchers and psychologists do not explicitly identify themselves with a certain perspective and instead take an eclectic approach. Research in this area is empirically driven – such as dimensional models, based on multivariate statistics such as factor analysis – or emphasizes theory development, such as that of the psychodynamic theory. There is also a substantial emphasis on the applied field of personality testing. In psychological education and training, the study of the nature of personality and its psychological development is usually reviewed as a prerequisite to courses in abnormal psychology or clinical psychology.

Philosophical assumptions

Many of the ideas conceptualized by historical and modern personality theorists stem from the basic philosophical assumptions they hold. The study of personality is not a purely empirical discipline, as it brings in elements of art, science, and philosophy to draw general conclusions. The following five categories are some of the most fundamental philosophical assumptions on which theorists disagree:

• Freedom versus determinism – This is the question of whether humans have control over their own behavior and understand the motives behind it, or if their behavior is causally determined by forces beyond their control. Behavior is categorized as being either unconscious, environmental or biological by various theories.
• Heredity (nature) versus environment (nurture) – Personality is thought to be determined largely either by genetics and biology, or by environment and experiences. Contemporary research suggests that most personality traits are based on the joint influence of genetics and environment. One of the forerunners in this arena is C. Robert Cloninger, who pioneered the Temperament and Character model.
• Uniqueness versus universality – This question discusses the extent of each human's individuality (uniqueness) or similarity in nature (universality). Gordon Allport, Abraham Maslow, and Carl Rogers were all advocates of the uniqueness of individuals. Behaviorists and cognitive theorists, in contrast, emphasize the importance of universal principles, such as reinforcement and self-efficacy.
• Active versus reactive – This question explores whether humans primarily act through individual initiative (active) or through outside stimuli. Traditional behavioral theorists typically believed that humans are passively shaped by their environments, whereas humanistic and cognitive theorists believe that humans play a more active role. Most modern theorists agree that both are important, with aggregate behavior being primarily determined by traits and situational factors being the primary predictor of behavior in the short term.
• Optimistic versus pessimistic – Personality theories differ with regard to whether humans are integral in the changing of their own personalities. Theories that place a great deal of emphasis on learning are often more optimistic than those that do not.

Personality theories

Type theories

Behavioral and psychological characteristics distinguishing introversion and extraversion, which are generally conceived as lying along a continuum.

Personality type refers to the psychological classification of people into different classes. Personality types are distinguished from personality traits, which come in different degrees. There are many theories of personality, but each one contains several and sometimes many sub theories. A "theory of personality" constructed by any given psychologist will contain multiple relating theories or sub theories often expanding as more psychologists explore the theory. For example, according to type theories, there are two types of people, introverts and extroverts. According to trait theories, introversion and extroversion are part of a continuous dimension with many people in the middle. The idea of psychological types originated in the theoretical work of Carl Jung, specifically in his 1921 book Psychologische Typen (Psychological Types) and William Marston.

Building on the writings and observations of Jung during World War II, Isabel Briggs Myers and her mother, Katharine C. Briggs, delineated personality types by constructing the Myers–Briggs Type Indicator. This model was later used by David Keirsey with a different understanding from Jung, Briggs and Myers. In the former Soviet Union, Lithuanian Aušra Augustinavičiūtė independently derived a model of personality type from Jung's called socionics. Later on many other tests were developed on this model e.g. Golden, PTI-Pro and JTI.

Theories could also be considered an "approach" to personality or psychology and is generally referred to as a model. The model is an older and more theoretical approach to personality, accepting extroversion and introversion as basic psychological orientations in connection with two pairs of psychological functions:

• Perceiving functions: sensing and intuition (trust in concrete, sensory-oriented facts vs. trust in abstract concepts and imagined possibilities)
• Judging functions: thinking and feeling (basing decisions primarily on logic vs. deciding based on emotion).

Briggs and Myers also added another personality dimension to their type indicator to measure whether a person prefers to use a judging or perceiving function when interacting with the external world. Therefore, they included questions designed to indicate whether someone wishes to come to conclusions (judgement) or to keep options open (perception).

This personality typology has some aspects of a trait theory: it explains people's behavior in terms of opposite fixed characteristics. In these more traditional models, the sensing/intuition preference is considered the most basic, dividing people into "N" (intuitive) or "S" (sensing) personality types. An "N" is further assumed to be guided either by thinking or feeling and divided into the "NT" (scientist, engineer) or "NF" (author, humanitarian) temperament. An "S", in contrast, is assumed to be guided more by the judgment/perception axis and thus divided into the "SJ" (guardian, traditionalist) or "SP" (performer, artisan) temperament. These four are considered basic, with the other two factors in each case (including always extraversion/introversion) less important. Critics of this traditional view have observed that the types can be quite strongly stereotyped by professions (although neither Myers nor Keirsey engaged in such stereotyping in their type descriptions), and thus may arise more from the need to categorize people for purposes of guiding their career choice. This among other objections led to the emergence of the five-factor view, which is less concerned with behavior under work conditions and more concerned with behavior in personal and emotional circumstances. (The MBTI is not designed to measure the "work self", but rather what Myers and McCaulley called the "shoes-off self.")

Type A and Type B personality theory: During the 1950s, Meyer Friedman and his co-workers defined what they called Type A and Type B behavior patterns. They theorized that intense, hard-driving Type A personalities had a higher risk of coronary disease because they are "stress junkies." Type B people, on the other hand, tended to be relaxed, less competitive, and lower in risk. There was also a Type AB mixed profile.

John L. Holland's RIASEC vocational model, commonly referred to as the Holland Codes, stipulates that six personality types lead people to choose their career paths. In this circumplex model, the six types are represented as a hexagon, with adjacent types more closely related than those more distant. The model is widely used in vocational counseling.

Eduard Spranger's personality-model, consisting of six (or, by some revisions, 6 +1) basic types of value attitudes, described in his book Types of Men (Lebensformen; Halle (Saale): Niemeyer, 1914; English translation by P. J. W. Pigors - New York: G. E. Stechert Company, 1928).

The Enneagram of Personality, a model of human personality which is principally used as a typology of nine interconnected personality types. It has been criticized as being subject to interpretation, making it difficult to test or validate scientifically.

Perhaps the most ancient attempt at personality psychology is the personality typology outlined by the Indian Buddhist Abhidharma schools. This typology mostly focuses on negative personal traits (greed, hatred, and delusion) and the corresponding positive meditation practices used to counter those traits.

Psychoanalytical theories

Psychoanalytic theories explain human behavior in terms of the interaction of various components of personality. Sigmund Freud was the founder of this school of thought. He drew on the physics of his day (thermodynamics) to coin the term psychodynamics. Based on the idea of converting heat into mechanical energy, Freud proposed psychic energy could be converted into behavior. His theory places central importance on dynamic, unconscious psychological conflicts.

Freud divides human personality into three significant components: the id, ego and super-ego. The id acts according to the pleasure principle, demanding immediate gratification of its needs regardless of external environment; the ego then must emerge in order to realistically meet the wishes and demands of the id in accordance with the outside world, adhering to the reality principle. Finally, the superego (conscience) inculcates moral judgment and societal rules upon the ego, thus forcing the demands of the id to be met not only realistically but morally. The superego is the last function of the personality to develop, and is the embodiment of parental/social ideals established during childhood. According to Freud, personality is based on the dynamic interactions of these three components.

The channeling and release of sexual (libidal) and aggressive energies, which ensues from the "Eros" (sex; instinctual self-preservation) and "Thanatos" (death; instinctual self-annihilation) drives respectively, are major components of his theory. It is important to note that Freud's broad understanding of sexuality included all kinds of pleasurable feelings experienced by the human body.

Freud proposed five psychosexual stages of personality development. He believed adult personality is dependent upon early childhood experiences and largely determined by age five. Fixations that develop during the infantile stage contribute to adult personality and behavior.

One of Sigmund Freud's earlier associates, Alfred Adler, agreed with Freud that early childhood experiences are important to development, and believed birth order may influence personality development. Adler believed that the oldest child was the individual who would set high achievement goals in order to gain attention lost when the younger siblings were born. He believed the middle children were competitive and ambitious. He reasoned that this behavior was motivated by the idea of surpassing the firstborn's achievements. He added, however, that the middle children were often not as concerned about the glory attributed to their behavior. He also believed the youngest would be more dependent and sociable. Adler finished by surmising that an only child loves being the center of attention and matures quickly but in the end fails to become independent.

Heinz Kohut thought similarly to Freud's idea of transference. He used narcissism as a model of how people develop their sense of self. Narcissism is the exaggerated sense of self in which one is believed to exist in order to protect one's low self-esteem and sense of worthlessness. Kohut had a significant impact on the field by extending Freud's theory of narcissism and introducing what he called the 'self-object transferences' of mirroring and idealization. In other words, children need to idealize and emotionally "sink into" and identify with the idealized competence of admired figures such as parents or older siblings. They also need to have their self-worth mirrored by these people. Such experiences allow them to thereby learn the self-soothing and other skills that are necessary for the development of a healthy sense of self.

Another important figure in the world of personality theory is Karen Horney. She is credited with the development of "Feminist Psychology". She disagrees with Freud on some key points, one being that women's personalities are not just a function of "Penis Envy", but that girl children have separate and different psychic lives unrelated to how they feel about their fathers or primary male role models. She talks about three basic Neurotic needs "Basic Anxiety", "Basic Hostility" and "Basic Evil". She posits that to any anxiety an individual experiences they would have one of three approaches, moving toward people, moving away from people or moving against people. It is these three that give us varying personality types and characteristics. She also places a high premium on concepts like Overvaluation of Love and romantic partners.

Behaviorist theories

Behaviorists explain personality in terms of the effects external stimuli have on behavior. The approaches used to evaluate the behavioral aspect of personality are known as behavioral theories or learning-conditioning theories. These approaches were a radical shift away from Freudian philosophy. One of the major tenets of this concentration of personality psychology is a strong emphasis on scientific thinking and experimentation. This school of thought was developed by B. F. Skinner who put forth a model which emphasized the mutual interaction of the person or "the organism" with its environment. Skinner believed children do bad things because the behavior obtains attention that serves as a reinforcer. For example: a child cries because the child's crying in the past has led to attention. These are the response, and consequences. The response is the child crying, and the attention that child gets is the reinforcing consequence. According to this theory, people's behavior is formed by processes such as operant conditioning. Skinner put forward a "three term contingency model" which helped promote analysis of behavior based on the "Stimulus - Response - Consequence Model" in which the critical question is: "Under which circumstances or antecedent 'stimuli' does the organism engage in a particular behavior or 'response', which in turn produces a particular 'consequence'?"

Richard Herrnstein extended this theory by accounting for attitudes and traits. An attitude develops as the response strength (the tendency to respond) in the presences of a group of stimuli become stable. Rather than describing conditionable traits in non-behavioral language, response strength in a given situation accounts for the environmental portion. Herrstein also saw traits as having a large genetic or biological component, as do most modern behaviorists.

Ivan Pavlov is another notable influence. He is well known for his classical conditioning experiments involving dogs, which led him to discover the foundation of behaviorism.

Social cognitive theories

In cognitive theory, behavior is explained as guided by cognitions (e.g. expectations) about the world, especially those about other people. Cognitive theories are theories of personality that emphasize cognitive processes, such as thinking and judging.

Albert Bandura, a social learning theorist suggested the forces of memory and emotions worked in conjunction with environmental influences. Bandura was known mostly for his "Bobo doll experiment". During these experiments, Bandura video taped a college student kicking and verbally abusing a bobo doll. He then showed this video to a class of kindergarten children who were getting ready to go out to play. When they entered the play room, they saw bobo dolls, and some hammers. The people observing these children at play saw a group of children beating the doll. He called this study and his findings observational learning, or modeling.

Early examples of approaches to cognitive style are listed by Baron (1982). These include Witkin's (1965) work on field dependency, Gardner's (1953) discovering people had consistent preference for the number of categories they used to categorise heterogeneous objects, and Block and Petersen's (1955) work on confidence in line discrimination judgments. Baron relates early development of cognitive approaches of personality to ego psychology. More central to this field have been:

• Attributional style theory dealing with different ways in which people explain events in their lives. This approach builds upon locus of control, but extends it by stating we also need to consider whether people attribute to stable causes or variable causes, and to global causes or specific causes.

Various scales have been developed to assess both attributional style and locus of control. Locus of control scales include those used by Rotter and later by Duttweiler, the Nowicki and Strickland (1973) Locus of Control Scale for Children and various locus of control scales specifically in the health domain, most famously that of Kenneth Wallston and his colleagues, The Multidimensional Health Locus of Control Scale. Attributional style has been assessed by the Attributional Style Questionnaire, the Expanded Attributional Style Questionnaire, the Attributions Questionnaire, the Real Events Attributional Style Questionnaire and the Attributional Style Assessment Test.

• Achievement style theory focuses upon identification of an individual's Locus of Control tendency, such as by Rotter's evaluations, and was found by Cassandra Bolyard Whyte to provide valuable information for improving academic performance of students. Individuals with internal control tendencies are likely to persist to better academic performance levels, presenting an achievement personality, according to Cassandra B. Whyte.

Recognition that the tendency to believe that hard work and persistence often results in attainment of life and academic goals has influenced formal educational and counseling efforts with students of various ages and in various settings since the 1970s research about achievement. Counseling aimed toward encouraging individuals to design ambitious goals and work toward them, with recognition that there are external factors that may impact, often results in the incorporation of a more positive achievement style by students and employees, whatever the setting, to include higher education, workplace, or justice programming.

Walter Mischel (1999) has also defended a cognitive approach to personality. His work refers to "Cognitive Affective Units", and considers factors such as encoding of stimuli, affect, goal-setting, and self-regulatory beliefs. The term "Cognitive Affective Units" shows how his approach considers affect as well as cognition.

Cognitive-Experiential Self-Theory (CEST) is another cognitive personality theory. Developed by Seymour Epstein, CEST argues that humans operate by way of two independent information processing systems: experiential system and rational system. The experiential system is fast and emotion-driven. The rational system is slow and logic-driven. These two systems interact to determine our goals, thoughts, and behavior.

Personal construct psychology (PCP) is a theory of personality developed by the American psychologist George Kelly in the 1950s. Kelly's fundamental view of personality was that people are like naive scientists who see the world through a particular lens, based on their uniquely organized systems of construction, which they use to anticipate events. But because people are naive scientists, they sometimes employ systems for construing the world that are distorted by idiosyncratic experiences not applicable to their current social situation. A system of construction that chronically fails to characterize and/or predict events, and is not appropriately revised to comprehend and predict one's changing social world, is considered to underlie psychopathology (or mental illness.) From the theory, Kelly derived a psychotherapy approach and also a technique called The Repertory Grid Interview that helped his patients to uncover their own "constructs" with minimal intervention or interpretation by the therapist. The repertory grid was later adapted for various uses within organizations, including decision-making and interpretation of other people's world-views.

Humanistic theories

Humanistic psychology emphasizes that people have free will and that this plays an active role in determining how they behave. Accordingly, humanistic psychology focuses on subjective experiences of persons as opposed to forced, definitive factors that determine behavior. Abraham Maslow and Carl Rogers were proponents of this view, which is based on the "phenomenal field" theory of Combs and Snygg (1949). Rogers and Maslow were among a group of psychologists that worked together for a decade to produce the Journal of Humanistic Psychology. This journal was primarily focused on viewing individuals as a whole, rather than focusing solely on separate traits and processes within the individual.

Robert W. White wrote the book The Abnormal Personality that became a standard text on abnormal psychology. He also investigated the human need to strive for positive goals like competence and influence, to counterbalance the emphasis of Freud on the pathological elements of personality development.

Maslow spent much of his time studying what he called "self-actualizing persons", those who are "fulfilling themselves and doing the best they are capable of doing". Maslow believes all who are interested in growth move towards self-actualizing (growth, happiness, satisfaction) views. Many of these people demonstrate a trend in dimensions of their personalities. Characteristics of self-actualizers according to Maslow include the four key dimensions:

1. Awareness – maintaining constant enjoyment and awe of life. These individuals often experienced a "peak experience". He defined a peak experience as an "intensification of any experience to the degree there is a loss or transcendence of self". A peak experience is one in which an individual perceives an expansion of themselves, and detects a unity and meaningfulness in life. Intense concentration on an activity one is involved in, such as running a marathon, may invoke a peak experience.
2. Reality and problem centered – having a tendency to be concerned with "problems" in surroundings.
3. Acceptance/Spontaneity – accepting surroundings and what cannot be changed.
4. Unhostile sense of humor/democratic – do not take kindly to joking about others, which can be viewed as offensive. They have friends of all backgrounds and religions and hold very close friendships.

Maslow and Rogers emphasized a view of the person as an active, creative, experiencing human being who lives in the present and subjectively responds to current perceptions, relationships, and encounters. They disagree with the dark, pessimistic outlook of those in the Freudian psychoanalysis ranks, but rather view humanistic theories as positive and optimistic proposals which stress the tendency of the human personality toward growth and self-actualization. This progressing self will remain the center of its constantly changing world; a world that will help mold the self but not necessarily confine it. Rather, the self has opportunity for maturation based on its encounters with this world. This understanding attempts to reduce the acceptance of hopeless redundancy. Humanistic therapy typically relies on the client for information of the past and its effect on the present, therefore the client dictates the type of guidance the therapist may initiate. This allows for an individualized approach to therapy. Rogers found patients differ in how they respond to other people. Rogers tried to model a particular approach to therapy – he stressed the reflective or empathetic response. This response type takes the client's viewpoint and reflects back their feeling and the context for it. An example of a reflective response would be, "It seems you are feeling anxious about your upcoming marriage". This response type seeks to clarify the therapist's understanding while also encouraging the client to think more deeply and seek to fully understand the feelings they have expressed.

Biopsychological theories

A large iron rod was driven through Gage's head, resulting in a personality change.

 

False-color represent­tations of cere­bral fiber path­ways affect­ed in Phineas Gage's accident, per Van Horn et al.

Biology plays a very important role in the development of personality. The study of the biological level in personality psychology focuses primarily on identifying the role of genetic determinants and how they mold individual personalities. Some of the earliest thinking about possible biological bases of personality grew out of the case of Phineas Gage. In an 1848 accident, a large iron rod was driven through Gage's head, and his personality apparently changed as a result, although descriptions of these psychological changes are usually exaggerated.

In general, patients with brain damage have been difficult to find and study. In the 1990s, researchers began to use electroencephalography (EEG), positron emission tomography (PET), and more recently functional magnetic resonance imaging (fMRI), which is now the most widely used imaging technique to help localize personality traits in the brain.

Genetic basis of personality

Ever since the Human Genome Project allowed for a much more in depth comprehension of genetics, there has been an ongoing controversy involving heritability, personality traits, and environmental vs. genetic influence on personality. The human genome is known to play a role in the development of personality.

Previously, genetic personality studies focused on specific genes correlating to specific personality traits. Today's view of the gene-personality relationship focuses primarily on the activation and expression of genes related to personality and forms part of what is referred to as behavioural genetics. Genes provide numerous options for varying cells to be expressed; however, the environment determines which of these are activated. Many studies have noted this relationship in varying ways in which our bodies can develop, but the interaction between genes and the shaping of our minds and personality is also relevant to this biological relationship.

DNA-environment interactions are important in the development of personality because this relationship determines what part of the DNA code is actually made into proteins that will become part of an individual. While different choices are made available by the genome, in the end, the environment is the ultimate determinant of what becomes activated. Small changes in DNA in individuals are what leads to the uniqueness of every person as well as differences in looks, abilities, brain functioning, and all the factors that culminate to develop a cohesive personality.

Cattell and Eysenck have proposed that genetics have a powerful influence on personality. A large part of the evidence collected linking genetics and the environment to personality have come from twin studies. This "twin method" compares levels of similarity in personality using genetically identical twins. One of the first of these twin studies measured 800 pairs of twins, studied numerous personality traits, and determined that identical twins are most similar in their general abilities. Personality similarities were found to be less related for self-concepts, goals, and interests.

Twin studies have also been important in the creation of the five factor personality model: neuroticism, extraversion, openness, agreeableness, and conscientiousness. Neuroticism and extraversion are the two most widely studied traits. Individuals scoring high in trait extraversion more often display characteristics such as impulsiveness, sociability, and activeness. Individuals scoring high in trait neuroticism are more likely to be moody, anxious, or irritable. Identical twins, however, have higher correlations in personality traits than fraternal twins. One study measuring genetic influence on twins in five different countries found that the correlations for identical twins were .50, while for fraternal they were about .20. It is suggested that heredity and environment interact to determine one's personality.

Evolutionary theory

Charles Darwin is the founder of the theory of the evolution of the species. The evolutionary approach to personality psychology is based on this theory. This theory examines how individual personality differences are based on natural selection. Through natural selection organisms change over time through adaptation and selection. Traits are developed and certain genes come into expression based on an organism's environment and how these traits aid in an organism's survival and reproduction.

Polymorphisms, such as sex and blood type, are forms of diversity which evolve to benefit a species as a whole. The theory of evolution has wide-ranging implications on personality psychology. Personality viewed through the lens of evolutionary biology places a great deal of emphasis on specific traits that are most likely to aid in survival and reproduction, such as conscientiousness, sociability, emotional stability, and dominance. The social aspects of personality can be seen through an evolutionary perspective. Specific character traits develop and are selected for because they play an important and complex role in the social hierarchy of organisms. Such characteristics of this social hierarchy include the sharing of important resources, family and mating interactions, and the harm or help organisms can bestow upon one another.

Drive theories

In the 1930s, John Dollard and Neal Elgar Miller met at Yale University, and began an attempt to integrate drives (see Drive theory), into a theory of personality, basing themselves on the work of Clark Hull. They began with the premise that personality could be equated with the habitual responses exhibited by an individual – their habits. From there, they determined that these habitual responses were built on secondary, or acquired drives.

Secondary drives are internal needs directing the behaviour of an individual that results from learning. Acquired drives are learned, by and large in the manner described by classical conditioning. When we are in a certain environment and experience a strong response to a stimulus, we internalize cues from the said environment. When we find ourselves in an environment with similar cues, we begin to act in anticipation of a similar stimulus. Thus, we are likely to experience anxiety in an environment with cues similar to one where we have experienced pain or fear – such as the dentist's office.

Secondary drives are built on primary drives, which are biologically driven, and motivate us to act with no prior learning process – such as hunger, thirst or the need for sexual activity. However, secondary drives are thought to represent more specific elaborations of primary drives, behind which the functions of the original primary drive continue to exist. Thus, the primary drives of fear and pain exist behind the acquired drive of anxiety. Secondary drives can be based on multiple primary drives and even in other secondary drives. This is said to give them strength and persistence. Examples include the need for money, which was conceptualized as arising from multiple primary drives such as the drive for food and warmth, as well as from secondary drives such as imitativeness (the drive to do as others do) and anxiety.

Secondary drives vary based on the social conditions under which they were learned – such as culture. Dollard and Miller used the example of food, stating that the primary drive of hunger manifested itself behind the learned secondary drive of an appetite for a specific type of food, which was dependent on the culture of the individual.

Secondary drives are also explicitly social, representing a manner in which we convey our primary drives to others. Indeed, many primary drives are actively repressed by society (such as the sexual drive). Dollard and Miller believed that the acquisition of secondary drives was essential to childhood development. As children develop, they learn not to act on their primary drives, such as hunger but acquire secondary drives through reinforcement. Friedman and Schustack describe an example of such developmental changes, stating that if an infant engaging in an active orientation towards others brings about the fulfillment of primary drives, such as being fed or having their diaper changed, they will develop a secondary drive to pursue similar interactions with others – perhaps leading to an individual being more gregarious. Dollard and Miller's belief in the importance of acquired drives led them to reconceive Sigmund Freud's theory of psychosexual development. They found themselves to be in agreement with the timing Freud used but believed that these periods corresponded to the successful learning of certain secondary drives.

Dollard and Miller gave many examples of how secondary drives impact our habitual responses – and by extension our personalities, including anger, social conformity, imitativeness or anxiety, to name a few. In the case of anxiety, Dollard and Miller note that people who generalize the situation in which they experience the anxiety drive will experience anxiety far more than they should. These people are often anxious all the time, and anxiety becomes part of their personality. This example shows how drive theory can have ties with other theories of personality – many of them look at the trait of neuroticism or emotional stability in people, which is strongly linked to anxiety.

Personality tests

There are two major types of personality tests, projective and objective.

Projective tests assume personality is primarily unconscious and assess individuals by how they respond to an ambiguous stimulus, such as an ink blot. Projective tests have been in use for about 60 years and continue to be used today. Examples of such tests include the Rorschach test and the Thematic Apperception Test.

The Rorschach Test involves showing an individual a series of note cards with ambiguous ink blots on them. The individual being tested is asked to provide interpretations of the blots on the cards by stating everything that the ink blot may resemble based on their personal interpretation. The therapist then analyzes their responses. Rules for scoring the test have been covered in manuals that cover a wide variety of characteristics such as content, originality of response, location of "perceived images" and several other factors. Using these specific scoring methods, the therapist will then attempt to relate test responses to attributes of the individual's personality and their unique characteristics. The idea is that unconscious needs will come out in the person's response, e.g. an aggressive person may see images of destruction.

The Thematic Apperception Test (TAT) involves presenting individuals with vague pictures/scenes and asking them to tell a story based on what they see. Common examples of these "scenes" include images that may suggest family relationships or specific situations, such as a father and son or a man and a woman in a bedroom. Responses are analyzed for common themes. Responses unique to an individual are theoretically meant to indicate underlying thoughts, processes, and potentially conflicts present within the individual. Responses are believed to be directly linked to unconscious motives. There is very little empirical evidence available to support these methods.

Objective tests assume personality is consciously accessible and that it can be measured by self-report questionnaires. Research on psychological assessment has generally found objective tests to be more valid and reliable than projective tests. Critics have pointed to the Forer effect to suggest some of these appear to be more accurate and discriminating than they really are. Issues with these tests include false reporting because there is no way to tell if an individual is answering a question honestly or accurately.

The Myers-Briggs Type Indicator (also known as the MBTI) is self-reporting questionnaire based on Carl Jung's Type theory. However, the MBTI modified Jung's theory into their own by disregarding certain processes held in the unconscious mind and the impact these have on personality.

Personality theory assessment criteria

• Verifiability – the theory should be formulated in such a way that the concepts, suggestions and hypotheses involved in it are defined clearly and unambiguously, and logically related to each other.
• Heuristic value – to what extent the theory stimulates scientists to conduct further research.
• Internal consistency – the theory should be free from internal contradictions.
• Economy – the fewer concepts and assumptions required by the theory to explain any phenomenon, the better it is Hjelle, Larry (1992). Personality Theories: Basic Assumptions, Research, and Applications.

Psychology has traditionally defined personality through its behavioral patterns, and more recently with neuroscientific studies of the brain. In recent years, some psychologists have turned to the study of inner experiences for insight into personality as well as individuality. Inner experiences are the thoughts and feelings to an immediate phenomenon. Another term used to define inner experiences is qualia. Being able to understand inner experiences assists in understanding how humans behave, act, and respond. Defining personality using inner experiences has been expanding due to the fact that solely relying on behavioral principles to explain one's character may seem incomplete. Behavioral methods allow the subject to be observed by an observer, whereas with inner experiences the subject is its own observer.^[56][57]

Methods measuring inner experience

Descriptive experience sampling (DES): Developed by psychologist Russel Hurlburt. This is an idiographic method that is used to help examine inner experiences. This method relies on an introspective technique that allows an individual's inner experiences and characteristics to be described and measured. A beep notifies the subject to record their experience at that exact moment and 24 hours later an interview is given based on all the experiences recorded. DES has been used in subjects that have been diagnosed with schizophrenia and depression. It has also been crucial to studying the inner experiences of those who have been diagnosed with common psychiatric diseases.

Articulated thoughts in stimulated situations (ATSS): ATSS is a paradigm which was created as an alternative to the TA (think aloud) method. This method assumes that people have continuous internal dialogues that can be naturally attended to. ATSS also assesses a person's inner thoughts as they verbalize their cognitions. In this procedure, subjects listen to a scenario via a video or audio player and are asked to imagine that they are in that specific situation. Later, they are asked to articulate their thoughts as they occur in reaction to the playing scenario. This method is useful in studying emotional experience given that the scenarios used can influence specific emotions. Most importantly, the method has contributed to the study of personality. In a study conducted by Rayburn and Davison (2002), subjects' thoughts and empathy toward anti-gay hate crimes were evaluated. The researchers found that participants showed more aggressive intentions towards the offender in scenarios which mimicked hate crimes.

Experimental method: This method is an experimental paradigm used to study human experiences involved in the studies of sensation and perception, learning and memory, motivation, and biological psychology. The experimental psychologist usually deals with intact organisms although studies are often conducted with organisms modified by surgery, radiation, drug treatment, or long-standing deprivations of various kinds or with organisms that naturally present organic abnormalities or emotional disorders. Economists and psychologists have developed a variety of experimental methodologies to elicit and assess individual attitudes where each emotion differs for each individual. The results are then gathered and quantified to conclude if specific experiences have any common factors. This method is used to seek clarity of the experience and remove any biases to help understand the meaning behind the experience to see if it can be generalized. The experimental method does have some complications though. If researchers are manipulating a variable, it's possible this change will affect a different variable, which in turn will change the measured result (not the original manipulated condition), introducing uncertainty. This method, in personality research, often requires deception, so the ethics of experiments are also brought into question.

Neural basis of self

From Wikipedia, the free encyclopedia

The neural basis of self is the idea of using modern concepts of neuroscience to describe and understand the biological processes that underlie humans' perception of self-understanding. The neural basis of self is closely related to the psychology of self with a deeper foundation in neurobiology.

Experimental techniques

In order to understand how the human mind makes the human perception of self, there are different experimental techniques. One of the more common methods of determining brain areas that pertain to different mental processes is by using Functional Magnetic Resonance Imaging. fMRI data is often used to determine activation levels in portions of the brain. fMRI measures blood flow in the brain. Areas with higher blood flow as shown on fMRI scans are said to be activated. This is due to the assumption that portions of the brain receiving increased blood flow are being used more heavily during the moment of scanning. Positron emission tomography is another method used to study brain activity.

Self-awareness

Anatomy

Brain areas involved human perception of self.

 

Brain areas involved human perception of self.

Two areas of the brain that are important in retrieving self-knowledge are the medial prefrontal cortex and the medial posterior parietal cortex. The posterior cingulate cortex, the anterior cingulate cortex, and medial prefrontal cortex are thought to combine to provide humans with the ability to self-reflect. The insular cortex is also thought to be involved in the process of self-reference.

Embodiment

The sense of embodiment is critical to a person's conception of self. Embodiment is the understanding of the physical body and its relation to oneself. The study of human embodiment currently has a large impact on the study of human cognition as a whole. The current study of embodiment suggests that sensory input and experiences impact human's overall perception. This idea somewhat challenges previous ideas of human cognition because it challenges the idea of the human mind being innate.

There are two portions of the brain that have recently been found to have a large importance on a person's perception of self. The temporoparietal junction, located in the cortex is one of these brain regions. The temporoparietal junction is thought to integrate sensory information. The second portion of the brain thought to be involved in perception of embodiment is the extrastriate body area. The extrastriate body area is located in the lateral occipitotemporal cortex. When people are shown images of body parts, the extrastriate body area is activated. The temporoparietal junction is involved in sensory integration processes while the extrastriate body area deals mainly with thoughts of and exposure to human body parts. It has been found that the brain responds to stimuli that involve embodiment differently from stimuli that involve localization. During task performance tests, a person's body position (whether he or she is sitting or laying face up) affects how the extrastriate body area is activated. The temporoparietal junction, however, is not affected by a person's particular body position. The temporoparietal junction deals with disembodied rather than embodied self-location, explaining why a person's physical position does not affect its activation. Self-location as related to a person's sense of embodiment is related to his or her actual location in space.

Autobiographical memories

The information people remember as autobiographical memory is essential to their perception of self. These memories form the way people feel about themselves. The left dorsolateral prefrontal cortex and posterior cingulate cortex are involved in the memory of autobiographical information.

Morality

Morality is an extremely important defining factor for humans. It often defines or contributes to people's choices or actions, defining who a person is. Making moral decisions, much like other neural processes has a clear biological basis. The anterior and medial prefrontal cortex and the superior temporal sulcus are activated when people feel guilt, compassion, or embarrassment. Guilt and passion activate the mesolimbic pathway, and indignation and disgust are activated by the amygdala. There is clearly a network involved with the ideas of morality.

Views of self

In order to explain how a human views him or herself, two different conceptual views of self-perception exist: the individualist and collectivistic views of self. The individualistic view of self involves people's perception of themselves as a stand-alone individual. This is thought of as a somewhat permanent perception of oneself that is unaffected by environmental and temporary cues and influences. People who view themselves in an individualistic sense describe themselves with personality traits that are permanent descriptions unrelated to particular situations. The collectivistic view of self, however, involves people's perception of themselves as members of a group or in a particular situation. The view people have of themselves in a collectivistic sense is entirely dependent on the situation they are in and the group with which they are interacting. These two ideas of self are also called self-construal styles. There is neurobiological evidence supporting these two definitions of self-construal styles. fMRI data has been used to understand the biology of both the individualistic and collectivistic view of self. Certain people tend to view themselves in almost exclusively a collectivistic sense or an individualistic sense. When people have to describe themselves in a collectivistic way (as a part of a group), those who tend to view themselves collectivistically show greater fMRI activation in the medial prefrontal cortex than those who view themselves individualistically. The reverse is true when people describe themselves individualistically.

Impaired views of self

The study of the human mind in diseased states provides valuable insight into how the mind works in healthy individuals. A multitude of diseases are studied to understand altered perceptions of self and what causes these impairments.

Autism

Autism is a disorder in which those affected experience impaired social interactions, communication, and behaviors. A new approach to studying autism is to focus on individuals’ perception of self rather than understanding the individual's social interactions. A common thought is that understanding of the differences between the self and others are impaired. However, the exact biological mechanism of self-understanding in autistic children is currently unknown. It has been found that there are significant differences in brain activation in self and other situations in autistic children when compared to children who do not have autism. In adults who do not have autism, during self-recognition tasks, the inferior frontal gyrus and the inferior parietal lobule in the right hemisphere are activated. Children who do not have autism show activation in these areas when performing face processing tasks for their own faces and those of others. Children with autism, however, only show activation in these areas when recognizing their own faces. The activation in the inferior frontal gyrus is less in children with autism than in those who do not have autism.

Schizophrenia

The cortical midline structure is extremely important in the understanding of the self, especially during the task of self-reflection. Many researchers believe that self-reference plays a role in the expression of psychoses. The disturbance of the individual's self may be underlying the manifestation of these psychoses. Occurrences such as hallucinations and delusions may originate with disruptions of a person's perception of the self. Understanding the differences in those who have psychoses and those who do not can aid in diagnoses and treatment of those diseases. Those who are prone to psychoses such as schizophrenia, when describing positive traits about themselves show increased activation in the left insula, right dorsomedial prefrontal cortex, and left ventromedial prefrontal cortex. When they use negative traits to describe themselves, those who are prone to psychoses show higher activation in the bilateral insula, anterior cingulate cortex, and right dorsomedial prefrontal cortex.

After strokes

Sometimes after strokes patients' perception of self changes. Often after a stroke, patients report their perception of self in more negative terms than before their stroke. 

Aging

It has been found that humans’ ideas of themselves are established early in life but that the perception can change as others ideas are combined with their own. There are differences in the areas activated during self-knowledge retrieval between adults and children. This suggests a difference in self-knowledge neurobiologically due to normal aging. The prefrontal cortex and the medial posterior parietal cortex have been found to be activated when adults perform self-knowledge retrieval processes. Tests consist of presenting subjects with self-description phrases and allowing the subject to respond yes or no depending on whether or not the phrase describes him or herself. During this task, patients brains are fMRI scanned. These results can then be compared to fMRI data of the same patients when they are asked if the same phrases describe another individual, such as a well-known fictional character. The medial prefrontal cortex is activated more strongly for subjects when they are describing themselves than when they are describing others. However, children show greater medial prefrontal cortex activation than adults when performing self-knowledge retrieval tasks. Additionally, children and adults activate different specific regions in the medial prefrontal cortex. Adults activate the posterior precuneus more while children activate the anterior precuneus and the posterior cingulate. The understanding of the areas of the brain most frequently activated in children and adults can also provide information about how children, adolescents, and adults view themselves differently. Older children more significantly activate the medial prefrontal cortex because they deal with introspection much less frequently than adults and adolescents. Children have decreased specificity in skills than adults, so they show greater activation during spatial tasks. This is explained by the idea that with increased expertise in a task, decreased interest in wide spatial parameters occurs. When a person is an expert, he or she is able to be more focused in his or her performance. The difference in performance between adults and children is thought to be attributable to different perceptions of the self whether it is more introspective or more concerned with the surroundings and environment.