Hindsight bias

From Wikipedia, the free encyclopedia

Hindsight bias, also known as the knew-it-all-along effect or creeping determinism, is the inclination, after an event has occurred, to see the event as having been predictable, despite there having been little or no objective basis for predicting it.^[1][2] It is a multifaceted phenomenon that can affect different stages of designs, processes, contexts, and situations.^[3] Hindsight bias may cause memory distortion, where the recollection and reconstruction of content can lead to false theoretical outcomes. It has been suggested that the effect can cause extreme methodological problems while trying to analyze, understand, and interpret results in experimental studies. A basic example of the hindsight bias is when, after viewing the outcome of a potentially unforeseeable event, a person believes he or she "knew it all along". Such examples are present in the writings of historians describing outcomes of battles, physicians recalling clinical trials, and in judicial systems trying to attribute responsibility and predictability of accidents.^[4]

History

The hindsight bias, although not thitherto named as such, was not a new concept when it emerged in psychological research in the 1970s. In fact, it had been indirectly described numerous times by historians, philosophers, and physicians.^[4] In 1973, Baruch Fischhoff attended a seminar where Paul E. Meehl stated an observation that clinicians often overestimate their ability to have foreseen the outcome of a particular case, as they claim to have known it all along.^[5] Baruch, a psychology graduate student at the time, saw an opportunity in psychological research to explain these observations.^[5]

Daniel Kahneman

In the early seventies, investigation of heuristics and biases was a large area of study in psychology, led by Amos Tversky and Daniel Kahneman.^[5] Two heuristics identified by Tversky and Kahneman were of immediate importance in the development of the hindsight bias; these were the availability heuristic and the representativeness heuristic.^[6] In an elaboration of these heuristics, Beyth and Fischhoff devised the first experiment directly testing the hindsight bias.^[7] They asked participants to judge the likelihood of several outcomes of US president Richard Nixon's upcoming visit to Beijing (then romanized as Peking) and Moscow. Some time after president Nixon's return, participants were asked to recall (or reconstruct) the probabilities they had assigned to each possible outcome, and their perceptions of likelihood of each outcome^[which?] was greater or overestimated for events that actually had occurred.^[7] This study is frequently referred to in definitions of the hindsight bias, and the title of the paper, "I knew it would happen", may have contributed to the hindsight bias being interchangeable with the phrase "knew it all along" hypothesis.

In 1975, Fischhoff developed another method for investigating the hindsight bias, which at the time was referred to as the "creeping determinism hypothesis".^[4] This method involves giving participants a short story with four possible outcomes, one of which they are told is true, and are then asked to assign the likelihood of each particular outcome.^[4] Participants frequently assign a higher likelihood of occurrence to whichever outcome they have been told is true.^[4] Remaining relatively unmodified, this method is still used in psychological and behavioural experiments investigating aspects of the hindsight bias. Having evolved from the heuristics of Tversky and Kahneman into the creeping determinism hypothesis and finally into the hindsight bias as we now know it, the concept has many practical applications and is still at the forefront of research today. Recent studies involving the hindsight bias have investigated the effect age has on the bias, how hindsight may impact interference and confusion, and how it may affect banking and investment strategies.^[8][9][10]

Factors and effects

The hindsight bias is defined as a tendency to change a recollection from an original thought to something different because of newly provided information.^[11] Since 1973, when Fischhoff started the hindsight bias research, there has been a focus on two main explanations of the bias: distorted event probabilities and distorted memory for judgments of factual knowledge.^[12]

Hindsight bias has been supported in tests done with examples of medical procedure and the outcome for the patient. Subjects are given the procedure and a randomly assigned patient outcome, either neutral or bad, to interpret the level of malpractice by the doctors. Results showed that higher levels of malpractice were reported by the subjects when they were told there was a bad patient outcome than a neutral patient outcome, even when presented with exactly the same procedure. This supported the hypothesis of the experiment that bias would increase when an adverse outcome was presented, even if it was false, and it was thought that treatment was overlooked only when the outcome was bad. During the experiment, subjects used the phrase "it should have been obvious" multiple times, which is reminiscent of one of the hindsight bias' other names: the "I knew it all along" phenomenon.^[13]

Affected bias

Hindsight bias is not only affected by whether or not the outcome is favorable or unfavorable, but also the severity of the negative outcome. In malpractice suits, the more severe the negative outcome the more dramatic the juror's hindsight bias. In a perfectly objective case, the verdict would be based on the physician's standard of care instead of the outcome of the treatment; however, studies show that cases that end in severe negative outcomes such as death result in higher levels of hindsight bias. In 1996, LaBine proposed a scenario where a psychiatric patient told a therapist that they were contemplating harming another individual who the therapist did not warn of possible danger. Three participants were given three possible outcomes where the threatened individual received no injuries, minor injuries, and serious injuries and then were asked to determine if the doctor would be considered negligent. Participants who received the serious injuries category not only rated the therapist as negligent but also rated the attack as more foreseeable. Participants in the no injuries and minor injury categories were more likely to see the therapist's actions as reasonable.^[14]

In tests for hindsight bias, a person is asked to remember a specific event from the past or recall some descriptive information that they had been tested on earlier. In between the first test and final test, they are given the correct information about the event or knowledge. At the final test, he or she will report that they knew the answer all along when they truly have changed their answer to fit with the correct information they were given after the initial test. Hindsight bias has been found to take place in both memory for experienced situations (events that the person is familiar with) and hypothetical situations (made up events where the person must imagine being involved).

More recently, it has been found that hindsight bias also exists in recall with visual material.^[12] When tested on initially blurry images, the subjects learn what the true image was after the fact and they would then remember a clear recognizable picture. There has been very little research on the phenomenon of visual hindsight bias. One experiment performed by Muhm et al. occurred over a six-year period and had over 4,618 participants. Each participant received a chest radiograph every 4 months. Each radiograph was reviewed by two radiologists and a respiratory physician to determine if there were any problems. Over the course of the experiment, 92 chest tumors were found in several of the participants. When physicians reviewed the previous radiographs of the participants who developed tumors, they determined that evidence of the tumor was present even before it had been identified. In other words, after finding the tumor, physicians determined the presence of the tumor was obvious in previous radiographs, even though they had not noticed it before.^[15]

The role of surprise

The role of surprise can help explain the malleability of hindsight bias. Surprise influences how the mind reconstructs pre-outcome predictions in three ways:

• Surprise is a direct metacognitive heuristic to estimate the distance between outcome and prediction.
• Surprise triggers a deliberate sense-making process.
• Surprise biases this process by enhancing the retrieval of surprise-congruent information and expectancy-based hypothesis testing.^[16]

Pezzo's sense-making model supports two contradicting ideas of a surprising outcome. The results can show a lesser hindsight bias or possibly a reversed effect, where the individual believes the outcome wasn't a possibility at all, or the outcome can lead to the hindsight bias being magnified to have a stronger effect. The sense-making process is triggered by an initial surprise. If the sense-making process does not complete and the sensory information is not detected or coded, the sensation is experienced as a surprise and the hindsight bias has a gradual reduction. When there is a lack of a sense-making process, the phenomena of reversed hindsight bias is created. Without the sense-making process being present, there is no remnant of thought about the surprise, therefore leading to a sensation of not believing the outcome as a possibility.^[16]

The role of personality

Along with the emotion of surprise, personality traits affect hindsight bias. A new integrative lens model is an approach to figure out the bias and accuracy in human inferences due to their individual personality traits. This model integrates on accurate personality judgments and hindsight effects as a by-product of knowledge updating.
During the study, three processes showed potential to explain the occurrence of hindsight effects in personality judgments:

• Changes in an individual's cue perceptions
• Changes in the use of more valid cues
• Changes in the consistency with which an individual applies cue knowledge

After two studies, it was clear that there were hindsight effects for each of the "Big Five" personality dimensions.
Evidence was found that both the utilization of more valid cues and changes in cue perceptions, but not changes in the consistency with which cue knowledge is applied account for the hindsight effects. During both studies, participants were presented with target pictures and were asked to judge each target's levels of the Big Five.^[17]

The role of age

It is more difficult to test for hindsight bias in children than adults because the verbal methods used in experiments on adults are too complex for children to understand, let alone measure bias. There have been some experimental procedures created with visual identification to test children in a way they can grasp. Methods with visual images start by presenting a blurry image that becomes clearer over time. In some conditions, the subjects know what the final object is, and in others they don't. In cases where the subject knows what the object shape will become when the image is clear, they are asked to estimate the amount of other participants of similar age will take to guess what the object is. Due to hindsight bias, the estimated times are often much lower than the actual times because the participant is using their knowledge while making their estimate.^[18]

These types of studies have presented results that show that the hindsight bias affects children as well as adults. Hindsight bias in adults and in children shares a core cognitive constraint. That constraint is a tendency to be biased on one's current knowledge when attempting to recall or reason about a more naïve cognitive state—regardless of whether that more naïve state is one's own earlier naïve state or someone else's. Children have a theory of mind, which is their mental state of reasoning. Hindsight bias is a fundamental problem in cognitive perspective-taking. After reviewing developmental literature on hindsight bias and other limitations, it was found that some of children's limitation in the theory of mind may stem from the same core component as hindsight bias. This key factor brings forth underlying mechanisms. A developmental approach is necessary for a comprehensive understanding of the nature of hindsight bias in social cognition.^[19]

Bernstein et al. ran an experiment that determined that hindsight bias was more prevalent in preschool aged children, decreased in older childhood and adulthood, and then increased again older adulthood. Results indicated that preschool aged children often exhibited hindsight bias by confusing their original answer with information that was presented to them at a later date. This led them to believe that they had known it all along. Older adults exhibited hindsight bias by forgetting their original answers and using the information presented at a later date to construct a new answer. Older children and adults displayed a different type of hindsight bias when presented with an identical task. After being presented with new information, older children and adults often adjusted their answers but did not formulate or adopt an entirely new idea. Regardless of age, all participants claimed to know more answers than they actually did.^[8]

Auditory distractions

Another topic that affects the function of hindsight bias is the auditory function of humans. To test the effects of auditory distractions on hindsight bias, four experiments were completed. Experiment one included plain words, experiment two included words with warning, experiment three included full sentences, and experiment four included less-degraded words. By using these different techniques, it offers a different range of detection. Knowing the identities of words caused people to overestimate others' naïve ability to identify moderately to highly degraded spoken versions of those words. People who know the outcome of an event tend to overestimate their own prior knowledge or others' naïve knowledge of the event. Speakers tend to overestimate the clarity of their message while listeners overestimate their understanding of communication. This hindsight bias creates a feeling of inevitability. This auditory hindsight bias occurs despite people's effort to avoid it.^[20]

Cognitive models

To understand how a person can so easily change the foundation of knowledge and belief for events after receiving new information, three cognitive models of hindsight bias have been reviewed.^[21] The three models are SARA (Selective Activation and Reconstructive Anchoring), RAFT (Reconstruction After Feedback with Take the best) and CMT (Causal Model Theory). SARA and RAFT focus on distortions or changes in a memory process, while CMT focuses on probability judgments of hindsight bias.

The SARA model, created by Rüdiger Pohl and associates, explains hindsight bias for descriptive information in memory and hypothetical situations.^[21][22] SARA assumes that people have a set of images to draw their memories from. They suffer from the hindsight bias due to selective activation or biased sampling of that set of images. Basically, people only remember small, select amounts of information—and when asked to recall it later, use that biased image to support their own opinions about the situation. The set of images is originally processed in the brain when first experienced. When remembered, this image reactivates, and the mind can edit and alter the memory, which takes place in hindsight bias when new and correct information is presented, leading one to believe that this new information when remembered at a later time is the persons original memory. Due to this reactivation in the brain, a more permanent memory trace can be created. The new information acts as a memory anchor causing retrieval impairment.^[23]

The RAFT model^[24] explains hindsight bias with comparisons of objects using knowledge-based probability then applying interpretations to those probabilities.^[21] When given two choices, a person recalls the information on both topics and makes assumptions based on how reasonable they find the information. An example case is someone comparing the size of two cities. If they know one city well (e.g. because it has a popular sporting team or through personal history) and know much less about the other, their mental cues for the more popular city increase. They then "take the best" option in their assessment of their own probabilities. For example, they recognize a city due to knowing of its sports team, and thus they assume that that city has the highest population. "Take the best" refers to a cue that is viewed as most valid and becomes support for the person's interpretations. RAFT is a by-product of adaptive learning. Feedback information updates a person's knowledge base. This can lead a person to be unable to retrieve the initial information, since the information cue has been replaced by a cue that they thought was more fitting. The "best" cue has been replaced, and the person only remembers the answer that is most likely and believes that they thought this was the best point the whole time.^[21]

Both SARA and RAFT descriptions include a memory trace impairment or cognitive distortion that is caused by feedback of information and reconstruction of memory.

CMT is a non-formal theory based on work by many researchers to create a collaborative process model for hindsight bias that involves event outcomes.^[21] People try to make sense of an event that has not turned out how they expected by creating causal reasoning for the starting event conditions. This can give that person the idea that the event outcome was inevitable and there was nothing that could take place to prevent it from happening. CMT can be caused by a discrepancy between a person's expectation of the event and the reality of an outcome. They consciously want to make sense of what has happened and selectively retrieve memory that supports the current outcome. The causal attribution can be motivated by wanting to feel more positive about the outcome, and possibly themselves.^[25]

Are people liars or are they tricking themselves into believing that they knew the right answer? These models would show that memory distortions and personal bias play a role.

Memory distortions

Hindsight bias has similarities to other memory distortions, such as misinformation effect and false autobiographical memory.^[11] Misinformation effect occurs after an event is witnessed; new information received after the fact influences how the person remembers the event, and can be called post-event misinformation. This is an important issue with eyewitness testimony. False autobiographical memory takes place when suggestions or additional outside information is provided to distort and change memory of events; this can also lead to false memory syndrome. At times this can lead to creation of new memories that are completely false and have not taken place.

All three of these memory distortions contain a three-stage procedure.^[11] The details of each procedure are different, but all three can result in some psychological manipulation and alteration of memory. Stage one is different between the three paradigms, although all involve an event, an event that has taken place (misinformation effect), an event that has not taken place (false autobiographical memory), and a judgment made by a person about an event that must be remembered (hindsight bias). Stage two consists of more information that is received by the person after the event has taken place. The new information given in hindsight bias is correct and presented upfront to the person, while the extra information for the other two memory distortions is wrong and presented in an indirect and possibly manipulative way. The third stage consists of recalling the starting information. The person must recall the original information with hindsight bias and misinformation effect, while a person that has a false autobiographical memory is expected to remember the incorrect information as a true memory.^[11]

Cavillo (2013) tested whether there is a relationship between the amount of time the experimenters gave the participants to respond and their level of bias when recalling their initial judgements. The results showed that there is in fact a relationship; the hindsight bias index was greater among the participants asked to respond rapidly than among participants allowed more time to respond.^[26]

To create a false autobiographical memory, the person must believe a memory that is not real. To seem real, the information must be influenced by their own personal judgments. There is no real episode of an event to remember, so this memory construction must be logical to that person's knowledge base. Hindsight bias and misinformation effect recall a specific time and event; this is called an episodic memory process.^[11] These two memory distortions both use memory-based mechanisms that involve a memory trace that has been changed. Hippocampus activation takes place when an episodic memory is recalled.^[27] The memory is then available for alteration by new information. The person believes that the remembered information is the original memory trace, not an altered memory. This new memory is made from accurate information, and therefore the person does not have much motivation to admit that they were wrong originally by remembering the original memory. This can lead to motivated forgetting.

Motivated forgetting

Following a negative outcome of a situation, people do not want to accept responsibility. Instead of accepting their role in the event, they might either view themselves as caught up in a situation that was unforeseeable with them therefore not being the culprits (this is referred to as defensive processing) or view the situation as inevitable with there therefore being nothing that could have been done to prevent it (this is retroactive pessimism).^[28] Defensive processing involves less hindsight bias, as they are playing ignorant of the event. Retroactive pessimism makes use of hindsight bias after a negative, unwanted outcome. Events in life can be hard to control or predict. It is no surprise that people want to view themselves in a more positive light and do not want to take responsibility for situations they could have altered. This leads to hindsight bias in the form of retroactive pessimism to inhibit upward counterfactual thinking, instead interpreting the outcome as succumbing to an inevitable fate.^[29]
This memory inhibition that prevents a person from recalling what really happened may lead to failure to accept mistakes, and therefore may make someone unable to learn and grow to prevent repeating the mistake.^[28] Hindsight bias can also lead to overconfidence in decisions without considering other options.^[30] Such people see themselves as persons who remember correctly, even though they are just forgetting that they were wrong. Avoiding responsibility is common among the human population. Examples are discussed below to show the regularity and severity of hindsight bias in society.

Elimination

Research shows that people still exhibit the bias even when they are informed about it.^[31] Researchers attempts to decrease the bias in participants has failed, leading one to think that hindsight bias has an automatic source in cognitive reconstruction. This supports the Causal Model Theory and the use of sense-making to understand event outcomes.^[21] The only observable way to decrease hindsight bias in testing is to have the participant think about how alternative hypotheses could be correct. This makes the participant doubt correct hypothesis and report that they would not have chosen it. However, this only decreases the hindsight bias, and there is not a solution to eliminate it.^[30]

Related disorders

Schizophrenia

Schizophrenia is an example of a disorder that directly affects the hindsight bias. Schizophrenic individuals are more strongly affected by the hindsight bias than are individuals from the general public.^[32]

The hindsight bias effect is a paradigm that demonstrates how recently acquired knowledge influences the recollection of past information. Recently acquired knowledge has a strange but strong influence on schizophrenic individuals in relation to information previous learned. New information combined with the lack of acceptable influence of past reality-based memories can disconfirm behaviour and delusional belief, which typify in patients suffering from schizophrenia.^[32] This can cause faulty memory, which can lead to hindsight thinking and believing in knowing something they don't.^[32] Delusion-prone individuals suffering from schizophrenia can falsely jump to conclusions.^[33] Jumping to conclusions can lead to hindsight, which strongly influences the delusional conviction in schizophrenic individuals.^[33] In numerous studies, cognitive functional deficits in schizophrenic individuals impair their ability to represent and uphold contextual processing.^[34]

Post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is the re-experiencing and avoidance of trauma-related stressors, emotions, and memories from a past event or events that has cognitive dramatizing impact on an individual.^[35] PTSD can be attributed to the functional impairment of the prefrontal cortex (PFC) structure. Dysfunctions of cognitive processing of context and abnormalities that PTSD patients suffer from can affect hindsight thinking, such as in combat soldiers perceiving they could have altered outcomes of events in war.^[36] The PFC and dopamine systems are parts of the brain that can be responsible for the impairment in cognitive control processing of context information. The PFC is well known for controlling the thought process in hindsight bias that something will happen when it evidently does not. Brain impairment in certain brain regions can also affect the thought process of an individual who may engage in hindsight thinking.^[37]

Cognitive flashbacks and other associated features from a traumatic event can trigger severe stress and negative emotions such as unpardonable guilt. For example, studies were done on trauma-related guilt characteristics of war veterans with chronic PTSD 8.^[38] Although there has been limited research, significant data suggests that hindsight bias has an effect on war veterans' personal perception of wrongdoing, in terms of guilt and responsibility from traumatic events of war. They blame themselves, and, in hindsight, perceive that they could have prevented what happened.

Examples

Health care system

Accidents are prone to happen in any human undertaking, but accidents occurring within the healthcare system seem more salient and severe due to their profound effect on the lives of those involved, sometimes resulting in the death of a patient. Hindsight bias has been shown to be a disadvantage of nearly all methods of measuring error and adverse events within the healthcare system.^[39] These methods include morbidity and mortality conferences, autopsies, case analysis, medical malpractice claims analysis, staff interviews, and even patient observation. Furthermore, studies of injury or death rates as a result of error and virtually all incident review procedures used in healthcare today fail to control for hindsight bias, severely limiting the generalizability and integrity of the research.^[40] Physicians who are primed with a possible diagnosis before evaluating the symptoms of a patient themselves are more likely to arrive at the primed diagnosis than physicians who were only given the symptoms of the patient.^[41] According to Harvard Medical Practice Studies, 44,000–98,000 deaths in the United States each year are a result of safety incidents within the healthcare system.^[39] Many of these deaths are considered preventable after the fact, clearly indicating the presence and importance of a hindsight bias in this field.

Judicial system

Hindsight bias results in being held to a higher standard in court. The defense is particularly susceptible to these effects, since their actions are the ones being scrutinized by the jury. Due to the hindsight bias, defendants are judged as capable of preventing the bad outcome.^[42] Though much stronger for the defendants, hindsight bias also affects the plaintiffs. In cases where there is an assumption of risk, hindsight bias may contribute to the jurors perceiving the event as riskier due to the poor outcome. This may lead the jury to feel that the plaintiff should have exercised greater caution in the situation. Both of these effects can be minimized if attorneys put the jury in a position of foresight rather than hindsight through the use of language and timelines. Encouraging people to explicitly think about the counterfactuals was an effective means of reducing the hindsight bias.^[43] In other words, people became less attached to the actual outcome and were more open to consider alternative lines of reasoning prior to the event. Judges involved in fraudulent transfer litigation cases were subject to the hindsight bias as well, resulting in an unfair advantage for the plaintiff,^[44] showing that jurors are not the only ones sensitive to the effects of the hindsight bias in the courtroom.

Fine-tuned Universe

From Wikipedia, the free encyclopedia

The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range, so that if any of several fundamental constants were only slightly different, the Universe would be unlikely to be conducive to the establishment and development of matter, astronomical structures, elemental diversity, or life as it is understood.^[1] The proposition is discussed among philosophers, scientists, theologians, and proponents and detractors of creationism.

Physicist Paul Davies has asserted that "There is now broad agreement among physicists and cosmologists that the Universe is in several respects ‘fine-tuned' for life". However, he continues, "the conclusion is not so much that the Universe is fine-tuned for life; rather it is fine-tuned for the building blocks and environments that life requires." He also states that "'anthropic' reasoning fails to distinguish between minimally biophilic universes, in which life is permitted, but only marginally possible, and optimally biophilic universes, in which life flourishes because biogenesis occurs frequently".^[2] Among scientists who find the evidence persuasive, a variety of natural explanations have been proposed, such as the anthropic principle along with multiple universes. George F. R. Ellis observes "that no possible astronomical observations can ever see those other universes. The arguments are indirect at best. And even if the multiverse exists, it leaves the deep mysteries of nature unexplained."^[3]

History

In 1913, the chemist Lawrence Joseph Henderson (1878–1942) wrote The Fitness of the Environment, one of the first books to explore concepts of fine tuning in the Universe. Henderson discusses the importance of water and the environment with respect to living things, pointing out that life depends entirely on the very specific environmental conditions on Earth, especially with regard to the prevalence and properties of water.^[4]

In 1961, the physicist Robert H. Dicke claimed that certain forces in physics, such as gravity and electromagnetism, must be perfectly fine-tuned for life to exist anywhere in the Universe.^[5][6] Fred Hoyle also argued for a fine-tuned Universe in his 1984 book Intelligent Universe. He compares "the chance of obtaining even a single functioning protein by chance combination of amino acids to a star system full of blind men solving Rubik's Cube simultaneously".^[7]

John Gribbin and Martin Rees wrote a detailed history and defence of the fine-tuning argument in their book Cosmic Coincidences (1989). According to Gribbin and Rees, carbon-based life was not haphazardly arrived at, but the deliberate end of a Universe "tailor-made for man."^{[8][page needed]}

Premise

The premise of the fine-tuned Universe assertion is that a small change in several of the dimensionless fundamental physical constants would make the Universe radically different. As Stephen Hawking has noted, "The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron. ... The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life."^[9]

If, for example, the strong nuclear force were 2% stronger than it is (i.e., if the coupling constant representing its strength were 2% larger), while the other constants were left unchanged, diprotons would be stable and hydrogen would fuse into them instead of deuterium and helium.^[10] This would drastically alter the physics of stars, and presumably preclude the existence of life similar to what we observe on Earth. The existence of the diproton would short-circuit the slow fusion of hydrogen into deuterium. Hydrogen would fuse so easily that it is likely that all of the Universe's hydrogen would be consumed in the first few minutes after the Big Bang.^[10] However, some of the fundamental constants describe the properties of the unstable strange, charmed, bottom and top quarks and mu and tau leptons that seem to play little part in the Universe or the structure of matter.^{[citation needed]}

The precise formulation of the idea is made difficult by the fact that physicists do not yet know how many independent physical constants there are. The current standard model of particle physics has 25 freely adjustable parameters with an additional parameter, the cosmological constant, for gravitation. However, because the standard model is not mathematically self-consistent under certain conditions (e.g., at very high energies, at which both quantum mechanics and general relativity are relevant), physicists believe that it is underlaid by some other theory, such as a grand unified theory, string theory, or loop quantum gravity. In some candidate theories, the actual number of independent physical constants may be as small as one. For example, the cosmological constant may be a fundamental constant, but attempts have also been made to calculate it from other constants, and according to the author of one such calculation, "the small value of the cosmological constant is telling us that a remarkably precise and totally unexpected relation exists among all the parameters of the Standard Model of particle physics, the bare cosmological constant and unknown physics."^[11]

Examples

Martin Rees formulates the fine-tuning of the Universe in terms of the following six dimensionless physical constants.^[12]

N, the ratio of the strength of electromagnetism to the strength of gravity for a pair of protons, is approximately 10³⁶. According to Rees, if it were significantly smaller, only a small and short-lived universe could exist.^[12]

Epsilon (ε), the strength of the force binding nucleons into nuclei, is 0.007. If it were 0.006, only hydrogen could exist, and complex chemistry would be impossible. If it were 0.008, no hydrogen would exist, as all the hydrogen would have been fused shortly after the big bang.^[12]

Omega (Ω), also known as the Density parameter, is the relative importance of gravity and expansion energy in the Universe. It is the ratio of the mass density of the Universe to the "critical density" and is approximately 1. If gravity were too strong compared with dark energy and the initial metric expansion, the Universe would have collapsed before life could have evolved. On the other side, if gravity were too weak, no stars would have formed.^[12]

Lambda (λ) is the cosmological constant. It describes the ratio of the density of dark energy to the critical energy density of the Universe, given certain reasonable assumptions such as positing that dark energy density is a constant. In terms of Planck units, and as a natural dimensionless value, the cosmological constant, λ, is on the order of 10⁻¹²².^[13] This is so small that it has no significant effect on cosmic structures that are smaller than a billion light-years across. If the cosmological constant was not extremely small, stars and other astronomical structures would not be able to form.^[12]

Q, the ratio of the gravitational energy required to pull a large galaxy apart to the energy equivalent of its mass, is around 10⁻⁵. If it is too small, no stars can form. If it is too large, no stars can survive because the Universe is too violent, according to Rees.^[12]

D, the number of spatial dimensions in spacetime, is 3. Rees claims that life could not exist if there were 2 or 4.^[12]

Carbon and oxygen

An older example is the Hoyle state, the third-lowest energy state of the carbon-12 nucleus, with an energy of 7.656 MeV above the ground level. According to one calculation, if the state's energy were lower than 7.3 or greater than 7.9 MeV, insufficient carbon would exist to support life; furthermore, to explain the Universe's abundance of carbon, the Hoyle state must be further tuned to a value between 7.596 and 7.716 MeV. A similar calculation, focusing on the underlying fundamental constants that give rise to various energy levels, concludes that the strong force must be tuned to a precision of at least 0.5%, and the electromagnetic force to a precision of at least 4%, to prevent either carbon production or oxygen production from dropping significantly.^[14]

Disputes regarding the existence and extent of fine-tuning

Physicist Victor Stenger objects to the fine-tuning, and especially to theist use of fine-tuning arguments. His numerous criticisms include what he calls "the wholly unwarranted assumption that only carbon-based life is possible."^[15] In turn, the astrophysicist Luke Barnes has criticised much of Stenger's work.^[16]

Fred Adams has investigated the existence of stars in universes with different values of the gravitational constant G, the fine-structure constant α, and a nuclear reaction rate parameter C. The study found that stars can exist in approximately 25% of the parameter space. His criteria of star existence is based on achieving sustained nuclear reaction and he suggests considering other factors, i.e. cosmic expansion, etc. in future work. The study addressed the question of whether stars can exist, not if life can exist -- asking the question about the life would introduce additional requirements that will place additional constraints.^[17]

The validity of fine tuning examples is sometimes questioned on the grounds that such reasoning is subjective anthropomorphism applied to natural physical constants. Critics also suggest that the fine-tuned Universe assertion and the anthropic principle are essentially tautologies.^[18]

The fine-tuned Universe argument has also been criticized as an argument by lack of imagination, as it assumes no other forms of life, sometimes referred to as carbon chauvinism. Conceptually, alternative biochemistry or other forms of life are possible.^[19] Regarding this, Stenger argues: "We have no reason to believe that our kind of carbon-based life is all that is possible. Furthermore, modern cosmology theorises that multiple universes may exist with different constants and laws of physics. So, it is not surprising that we live in the one suited for us. The Universe is not fine-tuned to life; life is fine-tuned to the Universe."^[20]

In addition, critics argue that humans are adapted to the Universe through the process of evolution, rather than the Universe being adapted to humans (see puddle thinking, below). They also see it as an example of the logical flaw of hubris or anthropocentrism in its assertion that humans are the purpose of the Universe.^[21]

Possible naturalistic explanations

There are fine tuning arguments that are naturalistic.^{[22][page needed]} As modern cosmology developed, various hypotheses have been proposed. One is an oscillatory universe or a multiverse, where fundamental physical constants are postulated to resolve themselves to random values in different iterations of reality.^[23] Under this hypothesis, separate parts of reality would have wildly different characteristics. In such scenarios, the issue of fine-tuning does not arise at all, as only those "universes" with constants hospitable to life (such as what we observe) would develop life capable of contemplating the question of the origin of fine-tuning.

Based upon the Anthropic principle, physicist Robert H. Dicke proposed the "Dicke coincidence" argument that the structure (age, physical constants, etc.) of the Universe as seen by living observers is not random, but is constrained by biological factors that require it to be roughly a "golden age".^[5]

Inflationary cosmology

Inflation theory posits that an inflaton field in the first 10⁻³⁰ seconds of the Universe produces strong repulsive gravity, and the Universe and space-time expand by a factor of 10³⁰. After 10⁻³⁰ seconds, gravity starts to become attractive. In this framework, with such rapid expansion, the overall shape of the Universe at 14 billion years is much less sensitive to initial parameters than the standard big bang model, and thus the fine-tuning issue disappears.^{[24][citation needed]}

Multiverse

The Multiverse hypothesis proposes the existence of many universes with different physical constants, some of which are hospitable to intelligent life (see multiverse: anthropic principle). Because we are intelligent beings, we are, by definition, in a hospitable universe.
This idea has led to considerable research into the anthropic principle and has been of particular interest to particle physicists, because theories of everything do apparently generate large numbers of universes in which the physical constants vary widely. As yet, there is no evidence for the existence of a multiverse, but some versions of the theory do make predictions that some researchers studying M-theory and gravity leaks hope to see some evidence of soon.^[25] Some multiverse theories are not falsifiable, thus scientists may be reluctant to call any multiverse theory "scientific". UNC-Chapel Hill professor Laura Mersini-Houghton claims that the WMAP cold spot may provide testable empirical evidence for a parallel universe,^[26] although this claim was recently refuted as the WMAP cold spot was found to be nothing more than a statistical artifact.^[27] Variants on this approach include Lee Smolin's notion of cosmological natural selection, the Ekpyrotic universe, and the Bubble universe theory.

Critics of the multiverse-related explanations argue that there is no evidence that other universes exist.

Bubble universe theory

The bubble universe model by physicist Andrei Linde postulates that our Universe is one of many that grew from a multiverse consisting of vacuum that had not yet decayed to its ground state.

According to this scenario, by means of a random quantum fluctuation, the Universe "tunneled" from pure vacuum ("nothing") to what is called a false vacuum, a region of space that contains no matter or radiation, but is not quite "nothing." The space inside this bubble of false vacuum was curved, or warped. A small amount of energy was contained in that curvature, somewhat like the energy stored in a strung bow. This ostensible violation of energy conservation is allowed by the Heisenberg uncertainty principle for sufficiently small time intervals. The bubble then inflated exponentially and the Universe grew by many orders of magnitude in a tiny fraction of a second. (For a not-too-technical discussion, see Stenger 1990^[28]). As the bubble expanded, its curvature energy was converted into matter and radiation, inflation stopped, and the more linear Big Bang expansion we now experience commenced. The Universe cooled and its structure spontaneously froze out, as formless water vapor freezes into snowflakes whose unique patterns arise from a combination of symmetry and randomness.

—Victor J. Stenger, The Anthropic Coincidences^[29]

In standard inflation, inflationary expansion occurred while the Universe was in a false vacuum state, halting when the Universe decayed to a true vacuum state. The bubble universe model proposes that different parts of this inflationary universe (termed a Multiverse) decayed at different times, with decaying regions corresponding to universes not in causal contact with each other. It further supposes that each bubble universe may have different physical constants.

Top-down cosmology

Stephen Hawking, along with Thomas Hertog of CERN, proposed that the Universe's initial conditions consisted of a superposition of many possible initial conditions, only a small fraction of which contributed to the conditions we see today.^[30] According to their theory, it is inevitable that we find our Universe's "fine-tuned" physical constants, as the current Universe "selects" only those past histories that led to the present conditions. In this way, top-down cosmology provides an anthropic explanation for why we find ourselves in a universe that allows matter and life, without invoking the existence of the Multiverse.^[31]

Alien design

One hypothesis is that the Universe may have been designed by extra-universal aliens. Some believe this would solve the problem of how a designer or design team capable of fine-tuning the Universe could come to exist.
Cosmologist Alan Guth believes humans will in time be able to generate new universes. By implication previous intelligent entities may have generated our Universe.^[32] This idea leads to the possibility that the extraterrestrial designer/designers are themselves the product of an evolutionary process in their own universe, which must therefore itself be able to sustain life. However it also raises the question of where this universe came from, leading to an infinite regress.

The Biocosm hypothesis and the Meduso-anthropic principle^{[citation needed]} both suggest that natural selection has made the Universe biophilic. The Universe enables intelligence because intelligent entities later create new biophilic universes. This is different from the suggestion above that aliens from a universe that is less-finely tuned than ours made our Universe finely tuned.

The Designer Universe theory of John Gribbin suggests that the Universe could have been made deliberately by a member or members of a technologically advanced civilization in another part of the Multiverse, and that this advanced civilization may have been responsible for causing the Big Bang.^[33]

Religious arguments

As with theistic evolution, some individual scientists, theologians, and philosophers as well as certain religious groups argue that providence or creation are responsible for fine-tuning.

Christian philosopher Alvin Plantinga argues that random chance, applied to a single and sole universe, only raises the question as to why this universe could be so "lucky" as to have precise conditions that support life at least at some place (the Earth) and time (within millions of years of the present).

One reaction to these apparent enormous coincidences is to see them as substantiating the theistic claim that the Universe has been created by a personal God and as offering the material for a properly restrained theistic argument—hence the fine-tuning argument. It's as if there are a large number of dials that have to be tuned to within extremely narrow limits for life to be possible in our Universe. It is extremely unlikely that this should happen by chance, but much more likely that this should happen, if there is such a person as God.

—Alvin Plantinga, The Dawkins Confusion; Naturalism ad absurdum^[34]

This fine-tuning of the Universe is cited^[35] by philosopher and Christian apologist William Lane Craig as an evidence for the existence of God or some form of intelligence capable of manipulating (or designing) the basic physics that governs the Universe. Craig argues, however, "that the postulate of a divine Designer does not settle for us the religious question."

Philosopher and theologian Richard Swinburne reaches the design conclusion using Bayesian probability.^{[36][page needed]}

Theologian Alister McGrath has pointed out that the fine-tuning of carbon is even responsible for nature’s ability to tune itself to any degree.

[The entire biological] evolutionary process depends upon the unusual chemistry of carbon, which allows it to bond to itself, as well as other elements, creating highly complex molecules that are stable over prevailing terrestrial temperatures, and are capable of conveying genetic information (especially DNA). […] Whereas it might be argued that nature creates its own fine-tuning, this can only be done if the primordial constituents of the universe are such that an evolutionary process can be initiated. The unique chemistry of carbon is the ultimate foundation of the capacity of nature to tune itself.^[37][38]

Theoretical physicist John Polkinghorne has stated: Anthropic fine tuning is too remarkable to be dismissed as just a happy accident.^[39]

Intelligent design

Proponents of Intelligent design argue that certain features of the Universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection. The fine-tuned Universe argument is a central premise or presented as given in many of the published works of prominent intelligent design proponents, such as William A. Dembski and Michael Behe.

Counter arguments

Mark Colyvan, Jay Garfield and Graham Priest (2005) have argued that a theistic explanation for fine tuning is faulted due to fallacious probabilistic reasoning.^[40]

Mathematician Michael Ikeda and astronomer William H. Jefferys have argued that the anthropic principle and selection effect are not properly taken into account in the fine tuning argument for a designer, and that in taking them into account, fine tuning does not support the designer hypothesis.^[41][42] Philosopher of science Elliott Sober makes a similar argument.^[43]

Richard Carrier utilized the work of Ikeda, Jefferys, and Sober, in a Bayesian analysis. He concludes that fine tuning is strong evidence against the existence of God.^{[44][page needed]}

Physicist Robert L. Park has also criticized the theistic interpretation of fine-tuning:

If the universe was designed for life, it must be said that it is a shockingly inefficient design. There are vast reaches of the universe in which life as we know it is clearly impossible: gravitational forces would be crushing, or radiation levels are too high for complex molecules to exist, or temperatures would make the formation of stable chemical bonds impossible... Fine-tuned for life? It would make more sense to ask why God designed a universe so inhospitable to life.^[45]

Victor Stenger argues that "The fine-tuning argument and other recent intelligent design arguments are modern versions of God-of-the-gaps reasoning, where a God is deemed necessary whenever science has not fully explained some phenomenon".^[15] Stenger argues that science may provide an explanation if a Theory of Everything is formulated, which he says may reveal connections between the physical constants. A change in one physical constant may be compensated by a change in another, suggesting that the apparent fine-tuning of the Universe is a fallacy because, in hypothesizing the apparent fine-tuning, it is mistaken to vary one physical parameter while keeping the others constant.^[46]

In popular culture

John C. Lennox discusses the fine-tuned Universe at length in God's Undertaker: Has Science Buried God? (2006).^{[citation needed]}

Robert J. Sawyer discusses the fine-tuned Universe at length in his novel Calculating God (2000).^{[citation needed]}

Author Neal Stephenson discussed the issue of fine-tuning in the conclusion to his essay In the Beginning... was the Command Line.^{[47][citation needed]}

Puddle theory is a term coined by Douglas Adams to satirize arguments that the Universe is made for man.^[48][49] As stated in Adams's book The Salmon of Doubt:^[50]

imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact, it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be all right, because this World was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.