Radiative cooling

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

Earth's longwave thermal radiation intensity, from clouds, atmosphere and surface.

In the study of heat transfer, radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation.

Radiative cooling has been applied in various contexts throughout human history, including ice making in India and Iran, heat shields for spacecraft, and in architecture. In 2014, a scientific breakthrough in the use of photonic metamaterials made daytime radiative cooling possible. It has since been proposed as a strategy to mitigate local and global warming caused by greenhouse gas emissions known as passive daytime radiative cooling.

Terrestrial radiative cooling

Mechanism

Infrared radiation can pass through dry, clear air in the wavelength range of 8–13 µm. Materials that can absorb energy and radiate it in those wavelengths exhibit a strong cooling effect. Materials that can also reflect 95% or more of sunlight in the 200 nanometres to 2.5 µm range can exhibit cooling even in direct sunlight.

Earth's energy budget

Further information: Earth's energy budget

The Earth-atmosphere system is radiatively cooled, emitting long-wave (infrared) radiation which balances the absorption of short-wave (visible light) energy from the sun.

Convective transport of heat, and evaporative transport of latent heat are both important in removing heat from the surface and distributing it in the atmosphere. Pure radiative transport is more important higher up in the atmosphere. Diurnal and geographical variation further complicate the picture.

The large-scale circulation of the Earth's atmosphere is driven by the difference in absorbed solar radiation per square meter, as the sun heats the Earth more in the Tropics, mostly because of geometrical factors. The atmospheric and oceanic circulation redistributes some of this energy as sensible heat and latent heat partly via the mean flow and partly via eddies, known as cyclones in the atmosphere. Thus the tropics radiate less to space than they would if there were no circulation, and the poles radiate more; however in absolute terms the tropics radiate more energy to space.

Nocturnal surface cooling

Radiative cooling is commonly experienced on cloudless nights, when heat is radiated into outer space from Earth's surface, or from the skin of a human observer. The effect is well-known among amateur astronomers.

The effect can be experienced by comparing skin temperature from looking straight up into a cloudless night sky for several seconds, to that after placing a sheet of paper between the face and the sky. Since outer space radiates at about a temperature of 3 K (−270.15 °C; −454.27 °F), and the sheet of paper radiates at about 300 K (27 °C; 80 °F) (around room temperature), the sheet of paper radiates more heat to the face than does the darkened cosmos. The effect is blunted by Earth's surrounding atmosphere, and particularly the water vapor it contains, so the apparent temperature of the sky is far warmer than outer space. The sheet does not block the cold, but instead reflects heat to the face and radiates the heat of the face that it just absorbed.

The same radiative cooling mechanism can cause frost or black ice to form on surfaces exposed to the clear night sky, even when the ambient temperature does not fall below freezing.

Kelvin's estimate of the Earth's age

Further information: Age of the Earth

The term radiative cooling is generally used for local processes, though the same principles apply to cooling over geological time, which was first used by Kelvin to estimate the age of the Earth (although his estimate ignored the substantial heat released by radioisotope decay, not known at the time, and the effects of convection in the mantle).

Astronomy

Radiative cooling is one of the few ways an object in space can give off energy. In particular, white dwarf stars are no longer generating energy by fusion or gravitational contraction, and have no solar wind. So the only way their temperature changes is by radiative cooling. This makes their temperature as a function of age very predictable, so by observing the temperature, astronomers can deduce the age of the star.

Applications

Climate change

Main article: Passive daytime radiative cooling

Passive radiative cooling technologies use the infrared window of 8–13 µm to radiate heat into outer space and impede solar absorption.

The widespread application of passive daytime radiative cooling (PDRC) technologies that use the infrared window (8–13 µm) to dissipate heat through longwave infrared (LWIR) thermal radiation heat transfer with outer space, has been proposed as a method of reducing temperature increases caused by climate change. The installation of passive radiative heat emission technologies has been proposed as necessary to lower the temperature of Earth at a fast enough rate for human survivability. Munday summarized the global implementation of such technologies:

Currently the Earth is absorbing ~1 W/m² more than it is emitting, which leads to an overall warming of the climate. By covering the Earth with a small fraction of thermally emitting materials, the heat flow away from the Earth can be increased, and the net radiative flux can be reduced to zero (or even made negative), thus stabilizing (or cooling) the Earth (...) If only 1%–2% of the Earth’s surface were instead made to radiate at this rate rather than its current average value, the total heat fluxes into and away from the entire Earth would be balanced and warming would cease.

PDRCs mimic the natural process of radiative cooling, in which the Earth cools itself by releasing heat to outer space (Earth's energy budget), although during the daytime, lowering ambient temperatures under direct solar intensity. On a clear day, solar irradiance can reach 1000 W/m² with a diffuse component between 50-100 W/m². The average PDRC has an estimated cooling power of ~100-150 W/m². The cooling power of PDRCs is proportional to the exposed surface area of the installation.

Architecture

Different roof materials absorb more or less heat. A higher roof albedo, or the whiter a roof, the higher its solar reflectance and heat emittance, which can reduce energy use and costs.

Cool roofs combine high solar reflectance with high infrared emittance, thereby simultaneously reducing heat gain from the sun and increasing heat removal through radiation. Radiative cooling thus offers potential for passive cooling for residential and commercial buildings. Traditional building surfaces, such as paint coatings, brick and concrete have high emittances of up to 0.96. They radiate heat into the sky to passively cool buildings at night. If made sufficiently reflective to sunlight, these materials can also achieve radiative cooling during the day.

The most common radiative coolers found on buildings are white cool-roof paint coatings, which have solar reflectances of up to 0.94, and thermal emittances of up to 0.96. The solar reflectance of the paints arises from optical scattering by the dielectric pigments embedded in the polymer paint resin, while the thermal emittance arises from the polymer resin. However, because typical white pigments like titanium dioxide and zinc oxide absorb ultraviolet radiation, the solar reflectances of paints based on such pigments do not exceed 0.95.

In 2014, researchers developed the first daytime radiative cooler using a multi-layer thermal photonic structure that selectively emits long wavelength infrared radiation into space, and can achieve 5 °C sub-ambient cooling under direct sunlight. Later researchers developed paintable porous polymer coatings, whose pores scatter sunlight to give solar reflectance of 0.96-0.99 and thermal emittance of 0.97. In experiments under direct sunlight, the coatings achieve 6 °C sub-ambient temperatures and cooling powers of 96 W/m².

Other notable radiative cooling strategies include dielectric films on metal mirrors, and polymer or polymer composites on silver or aluminum films. Silvered polymer films with solar reflectances of 0.97 and thermal emittance of 0.96, which remain 11 °C cooler than commercial white paints under the mid-summer sun, were reported in 2015. Researchers explored designs with dielectric silicon dioxide or silicon carbide particles embedded in polymers that are translucent in the solar wavelengths and emissive in the infrared. In 2017, an example of this design with resonant polar silica microspheres randomly embedded in a polymeric matrix, was reported. The material is translucent to sunlight and has infrared emissivity of 0.93 in the infrared atmospheric transmission window. When backed with silver coating, the material achieved a midday radiative cooling power of 93 W/m² under direct sunshine along with high-throughput, economical roll-to-roll manufacturing.

Heat shields

High emissivity coatings that facilitate radiative cooling may be used in reusable thermal protection systems (RTPS) in spacecraft and hypersonic aircraft. In such heat shields a high emissivity material, such as molybdenum disilicide (MoSi₂) is applied on a thermally insulating ceramic substrate. In such heat shields high levels of total emissivity, typically in the range 0.8 - 0.9, need to be maintained across a range of high temperatures. Planck's law dictates that at higher temperatures the radiative emission peak shifts to lower wavelengths (higher frequencies), influencing material selection as a function of operating temperature. In addition to effective radiative cooling, radiative thermal protection systems should provide damage tolerance and may incorporate self-healing functions through the formation of a viscous glass at high temperatures.

James Webb Space Telescope

The James Webb Space Telescope uses radiative cooling to reach its operation temperature of about 50 K. To do this, its large reflective sunshield blocks radiation from the Sun, Earth, and Moon. The telescope structure, kept permanently in shadow by the sunshield, then cools by radiation.

Nocturnal ice making in early India and Iran

See also: Yakhchāl

 

Radiative cooling energy budget

 

Ice Pool beside the Meybod yakhchāl in Iran

Before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common in both India and Iran.

In India, such apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards. Provided the air was calm and not too far above freezing, heat gain from the surrounding air by convection was low enough to allow the water to freeze.

In Iran, this involved making a large flat ice pools, which consisted of a reflection pool of water built on a bed of highly insulative material surrounded by high walls. The high walls provided protection against convective warming, the insulative material of the pool walls would protect against conductive heating from the ground, the large flat plane of water would then permit evaporative and radiative cooling to take place.

Psychosexual development

From Wikipedia, the free encyclopedia

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

In Freudian Ego psychology, psychosexual development is a central element of the psychoanalytic sexual drive theory. Freud believed that personality developed through a series of childhood stages in which pleasure seeking energies from the child became focused on certain erogenous areas. An erogenous zone is characterized as an area of the body that is particularly sensitive to stimulation. The five psychosexual stages are the oral, the anal, the phallic, the latent, and the genital. The erogenous zone associated with each stage serves as a source of pleasure. Being unsatisfied at any particular stage can result in fixation. On the other hand, being satisfied can result in a healthy personality. Sigmund Freud proposed that if the child experienced frustration at any of the psychosexual developmental stages, they would experience anxiety that would persist into adulthood as a neurosis, a functional mental disorder.

Background

The neurologist Sigmund Freud, c. 1921

Sigmund Freud (1856–1939) observed that during the predictable stages of early childhood development, the child's behavior is oriented towards certain parts of their body, e.g. the mouth during breast-feeding, the anus during toilet-training. He argued that adult neurosis (functional mental disorder) often is rooted in childhood sexuality, and consequently suggested that neurotic adult behaviors are manifestations of childhood sexual fantasy and desire. That is because human beings are born "polymorphous perverse", infants can derive sexual pleasure from any part of their bodies, and that socialization directs the instinctual libidinal drives into adult heterosexuality. Given the predictable timeline of childhood behavior, he proposed "libido development" as a model of normal childhood sexual development, wherein the child progresses through five psychosexual stages – the oral; the anal; the phallic; the latent; and the genital – in which the source pleasure is in a different erogenous zone.

Freudian psychosexual development

Sexual infantilism: in pursuing and satisfying their libido (sexual drive), the child might experience failure (parental and societal disapproval) and thus might associate anxiety with the given erogenous zone. To avoid anxiety, the child becomes fixated, preoccupied with the psychologic themes related to the erogenous zone in question. The fixation persists into adulthood and underlies the personality and psychopathology of the individual. It may manifest as mental ailments such as neurosis, hysteria, "female hysteria", or personality disorder.

Stage	Age Range	Erogenous zone	Consequences of psychologic fixation
Oral	Birth–1 year	Mouth	Orally aggressive: chewing gum and the ends of pencils, etc. Orally passive: smoking, eating, kissing, oral sexual practices Oral stage fixation might result in a passive, gullible, immature, manipulative personality.
Anal	1–3 years	Bowel and bladder elimination	Anal retentive: Obsessively organized, or excessively neat Anal expulsive: reckless, careless, defiant, disorganized, coprophiliac
Phallic	3–6 years	Genitalia	Oedipus complex (in boys and girls); according to Sigmund Freud. Electra complex (in girls); according to Carl Jung. Promiscuity and low self-esteem in both sexes.
Latency	6–puberty	Dormant sexual feelings	Immaturity and an inability to form fulfilling non-sexual relationships as an adult if fixation occurs in this stage.
Genital	Puberty–death	Sexual interests mature	Frigidity, impotence, sexual perversion, great difficulty in forming a healthy sexual relationship with another person

Oral stage

Main article: Oral stage

Oral needs may be satisfied by thumb-sucking.

The first stage of psychosexual development is the oral stage, spanning from birth until the age of one year, wherein the infant's mouth is the focus of libidinal gratification derived from the pleasure of feeding at the mother's breast, and from the oral exploration of their environment, i.e. the tendency to place objects in the mouth. The id dominates, because neither the ego nor the super ego is yet fully developed, and, since the infant has no personality (identity), every action is based upon the pleasure principle. Nonetheless, the infantile ego is forming during the oral stage; two factors contribute to its formation: (i) in developing a body image, they are discrete from the external world, e.g. the child understands pain when it is applied to their body, thus identifying the physical boundaries between body and environment; (ii) experiencing delayed gratification leads to understanding that specific behaviors satisfy some needs, e.g. crying gratifies certain needs.

Weaning is the key experience in the infant's oral stage of psychosexual development, their first feeling of loss consequent to losing the physical intimacy of feeding at mother's breast. Yet, weaning increases the infant's self-awareness that they do not control the environment, and thus learns of delayed gratification, which leads to the formation of the capacities for independence (awareness of the limits of the self) and trust (behaviors leading to gratification). Yet, thwarting of the oral-stage – too much or too little gratification of desire – might lead to an oral-stage fixation, characterized by passivity, gullibility, immaturity, unrealistic optimism, which is manifested in a manipulative personality consequent to ego malformation. In the case of too much gratification, the child does not learn that they do not control the environment, and that gratification is not always immediate, thereby forming an immature personality. In the case of too little gratification, the infant might become passive upon learning that gratification is not forthcoming, despite having produced the gratifying behavior.

Anal stage

Main article: Anal stage

A boy with open-crotch pants and diaper

The second stage of psychosexual development is the anal stage, spanning from the age of eighteen months to three years, wherein the infant's erogenous zone changes from the mouth (the upper digestive tract) to the anus (the lower digestive tract), while the ego formation continues. Toilet training is the child's key anal-stage experience, occurring at about the age of two years, and results in conflict between the id (demanding immediate gratification) and the ego (demanding delayed gratification) in eliminating bodily wastes, and handling related activities (e.g. manipulating excrement, coping with parental demands). The style of parenting influences the resolution of the id–ego conflict, which can be either gradual and psychologically uneventful, or which can be sudden and psychologically traumatic.

The ideal resolution of the id–ego conflict is in the child's adjusting to moderate parental demands that teach the value and importance of physical cleanliness and environmental order, thus producing a self-controlled adult. Yet, if the parents make immoderate demands of the child, by overemphasizing toilet training, it might lead to the development of a compulsive personality, a person too concerned with neatness and order. If the child obeys the id, and the parents yield, they might develop a self-indulgent personality characterized by personal slovenliness and environmental disorder. If the parents respond to that, the child must comply, but might develop a weak sense of self, because it was the parents' will, and not the child's ego, which controlled the toilet training.

Phallic stage

Main article: Phallic stage

The third stage of psychosexual development is the phallic stage, spanning the ages of three to six years, wherein the child's genitalia are their primary erogenous zone. It is in this third infantile development stage that children become aware of their bodies, the bodies of other children, and the bodies of their parents; they gratify physical curiosity by undressing and exploring each other as well as their genitals, and so learn the physical (sexual) differences between male and female and their associated social roles. In the phallic stage, a boy's decisive psychosexual experience is the Oedipus complex, his son–father competition for possession of mother. This psychological complex derives from the 5th-century BC Greek mythologic character Oedipus, who unwittingly killed his father, Laius, and sexually possessed his mother, Jocasta. Analogously, in the phallic stage, a girl's decisive psychosexual experience is the Electra complex, her daughter–mother competition for psychosexual possession of father. This psychological complex derives from the 5th-century BC Greek mythologic character Electra, who plotted matricidal revenge with Orestes, her brother, against Clytemnestra, their mother, and Aegisthus, their stepfather, for their murder of Agamemnon, their father, (cf. Electra, by Sophocles).

Initially, Freud equally applied the Oedipus complex to the psychosexual development of boys and girls, but later developed the female aspects of the theory as the feminine Oedipus attitude and the negative Oedipus complex; yet, it was his student–collaborator, Carl Jung, who coined the term Electra complex in 1913. Nonetheless, Freud rejected Jung's term as psychoanalytically inaccurate: "that what we have said about the Oedipus complex applies with complete strictness to the male child only, and that we are right in rejecting the term 'Electra complex', which seeks to emphasize the analogy between the attitude of the two sexes".

Oedipus complex: Oedipus explains the riddle of the Sphinx, Jean Auguste Dominique Ingres (c. 1805)

Electra complex: Electra at the Tomb of Agamemnon, by Frederic Leighton, c. 1869

Oedipus: Despite mother being the parent who primarily gratifies the child's desires, the child begins forming a discrete sexual identity – "boy", "girl" – that alters the dynamics of the parent and child relationship; the parents become the focus of infantile libidinal energy. The boy focuses his libido (sexual desire) upon his mother, and focuses jealousy and emotional rivalry against his father – because it is he who sleeps with mother. To facilitate uniting him with his mother, the boy's id wants to kill father (as did Oedipus), but the ego, pragmatically based upon the reality principle, knows that the father is the stronger of the two males competing to possess the one female. Nevertheless, the boy remains ambivalent about his father's place in the family, which is manifested as fear of castration by the physically greater father; the fear is an irrational, subconscious manifestation of the infantile Id.

Electra: Whereas boys develop castration anxiety, girls develop penis envy that is rooted in anatomic fact: without a penis, she cannot sexually possess mother, as the infantile id demands. As a result, the girl redirects her desire for sexual union upon father; thus, she progresses towards heterosexual femininity that culminates in bearing a child who replaces the absent penis. Moreover, after the phallic stage, the girl's psychosexual development includes transferring her primary erogenous zone from the infantile clitoris to the adult vagina. Freud thus considered a girl's Oedipal conflict to be more emotionally intense than that of a boy, potentially resulting in a submissive woman of insecure personality.

Psychologist Karen Horney has disputed this theory, calling it inaccurate and demeaning to women. She proposed that, in fact men experience feelings of inferiority because they cannot give birth to children, a concept she referred to as womb envy.

Psychologic defense: In both sexes, defense mechanisms provide transitory resolutions of the conflict between the drives of the Id and the drives of the ego. The first defense mechanism is repression, the blocking of memories, emotional impulses, and ideas from the conscious mind; yet it does not resolve the id–ego conflict. The second defense mechanism is Identification, by which the child incorporates, to their ego, the personality characteristics of the same-sex parent; in so adapting, the boy diminishes his castration anxiety, because his likeness to father protects him from father's wrath as a rival for mother; by so adapting, the girl facilitates identifying with mother, who understands that, in being females, neither of them possesses a penis, and thus they are not antagonists.

Dénouement: Unresolved psychosexual competition for the opposite-sex parent might produce a phallic-stage fixation leading a girl to become a woman who continually strives to dominate men (viz. penis envy), either as an unusually seductive woman (high self-esteem) or as an unusually submissive woman (low self-esteem). In a boy, a phallic-stage fixation might lead him to become an aggressive, over-ambitious, vain man. Therefore, the satisfactory parental handling and resolution of the Oedipus complex and of the Electra complex are most important in developing the infantile super-ego, because, by identifying with a parent, the child internalizes morality, thereby, choosing to comply with societal rules, rather than having to reflexively comply in fear of punishment.

Latency stage

Main article: Latency stage

The fourth stage of psychosexual development is the latency stage that spans from the age of six years until puberty, wherein the child consolidates the character habits they developed in the three earlier stages of psychologic and sexual development. Whether or not the child has successfully resolved the Oedipal conflict, the instinctual drives of the child are inaccessible to the ego, because their defense mechanisms repressed them during the phallic stage. Hence, because said drives are latent (hidden) and gratification is delayed – unlike during the preceding oral, anal, and phallic stages – the child must derive the pleasure of gratification from secondary process-thinking that directs the libidinal drives towards external activities, such as schooling, friendships, hobbies, etc. Any neuroses established during the fourth, latent stage, of psychosexual development might derive from the inadequate resolution either of the Oedipus conflict or of the ego's failure to direct their energies towards socially acceptable activities.

Genital stage

Main article: Genital stage

The fifth stage of psychosexual development is the genital stage that spans puberty through adult life, and thus represents most of a person's life; its purpose is the psychological detachment and independence from the parents. The genital stage affords the person the ability to confront and resolve their remaining psychosexual childhood conflicts. As in the phallic stage, the genital stage is centered upon the genitalia, but the sexuality is consensual and adult, rather than solitary and infantile. The psychological difference between the phallic and genital stages is that the ego is established in the latter; the person's concern shifts from primary-drive gratification (instinct) to applying secondary process-thinking to gratify desire symbolically and intellectually by means of friendships, a love relationship, family and adult responsibility.

Criticisms

Scientific

A criticism of the scientific validity of the psychoanalytical theory of human psychosexual development is that Sigmund Freud was personally fixated upon human sexuality. According to this criticism, he favored defining human development with a normative theory of psychologic and sexual development. The phallic stage proved more complex, as it drew on clinical observations that Freud interpreted as supporting the Oedipus complex.

Freud stated that his patients commonly had memories and fantasies of childhood seduction. Critics hold that these were more likely to have been constructs which Freud created and forced upon his patients. According to Frederick Crews, the seduction theory that Freud abandoned in the late 1890s acted as a precedent to the wave of false allegations of childhood sexual abuse in the 1980s and 1990s.

Feminist

Main article: Feminist views on the Oedipus complex

Some feminists criticize Freud's psychosexual development theory as being sexist and phallocentric, arguing that it was overly informed by his own self-analysis. In response to the Freudian concept of penis envy in the development of the feminine Oedipus complex, the German Neo-Freudian psychoanalyst Karen Horney, counter-proposed that girls instead develop "Power envy" rather than penis envy. She also proposed the concept of "womb and vagina envy", the male's envy of the female ability to bear children. Some contemporary theorists suggest, in addition to this, the envy of the woman's perceived right to be the kind parent.

Anthropologic

Bronisław Malinowski and natives, Trobriand Islands (1918)

Contemporary cultural considerations have questioned the normative presumptions of the Freudian psychodynamic perspective that posits the son–father conflict of the Oedipal complex as universal and essential to human psychologic development.

The anthropologist Bronisław Malinowski's studies of the Trobriand islanders challenged the Freudian proposal that psychosexual development (e.g. the Oedipus complex) was universal. He reported that in the insular matriarchal society of the Trobriand, boys are disciplined by their maternal uncles, not their fathers (impartial, avuncular discipline). In Sex and Repression in Savage Society (1927), Malinowski reported that boys dreamed of feared uncles, not of beloved fathers, thus, power – not sexual jealousy – is the source of Oedipal conflict in such non–Western societies. Furthermore, contemporary research confirms that although personality traits corresponding to the oral stage, the anal stage, the phallic stage, the latent stage, and the genital stage are observable, they remain undetermined as fixed stages of childhood, and as adult personality traits derived from childhood.

Iconic memory

From Wikipedia, the free encyclopedia

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

Iconic memory is the visual sensory memory register pertaining to the visual domain and a fast-decaying store of visual information. It is a component of the visual memory system which also includes visual short-term memory (VSTM) and long-term memory (LTM). Iconic memory is described as a very brief (<1 second), pre-categorical, high capacity memory store. It contributes to VSTM by providing a coherent representation of our entire visual perception for a very brief period of time. Iconic memory assists in accounting for phenomena such as change blindness and continuity of experience during saccades. Iconic memory is no longer thought of as a single entity but instead, is composed of at least two distinctive components. Classic experiments including Sperling's partial report paradigm as well as modern techniques continue to provide insight into the nature of this SM store.

Overview

The occurrence of a sustained physiological image of an object after its physical offset has been observed by many individuals throughout history. One of the earliest documented accounts of the phenomenon was by Aristotle who proposed that afterimages were involved in the experience of a dream. Natural observation of the light trail produced by glowing ember at the end of a quickly moving stick sparked the interest of researchers in the 1700s and 1800s. They became the first to begin empirical studies on this phenomenon which later became known as visible persistence. In the 1900s, the role of visible persistence in memory gained considerable attention due to its hypothesized role as a pre-categorical representation of visual information in visual short-term memory (VSTM). In 1960, George Sperling began his classic partial-report experiments to confirm the existence of visual sensory memory and some of its characteristics including capacity and duration. It was not until 1967 that Ulric Neisser termed this quickly decaying memory store iconic memory. Approximately 20 years after Sperling's original experiments, two separate components of visual sensory memory began to emerge: visual persistence and informational persistence. Sperling's experiments mainly tested the information pertaining to a stimulus, whereas others such as Coltheart performed directs tests of visual persistence. In 1978, Di Lollo proposed a two-state model of visual sensory memory. Although it has been debated throughout history, current understanding of iconic memory makes a clear distinction between visual and informational persistence which are tested differently and have fundamentally different properties. Informational persistence which is the basis behind iconic memory is thought to be the key contributor to visual short-term memory as the precategorical sensory store. A similar storage area serves as a temporary warehouse for sounds.

Components

The two main components of iconic memory are visible persistence and informational persistence. The first is a relatively brief (150 ms) pre-categorical visual representation of the physical image created by the sensory system. This would be the "snapshot" of what the individual is looking at and perceiving. The second component is a longer-lasting memory store which represents a coded version of the visual image into post-categorical information. This would be the "raw data" that is taken in and processed by the brain. A third component may also be considered which is neural persistence: the physical activity and recordings of the visual system. Neural persistence is generally represented by neuroscientific techniques such as EEG and fMRI.

Visible persistence

Visible persistence is the phenomenal impression that a visual image remains present after its physical offset. This can be considered a by-product of neural persistence. Visible persistence is more sensitive to the physical parameters of the stimulus than informational persistence which is reflected in its two key properties.:

1. The duration of visible persistence is inversely related to stimulus duration. This means that the longer the physical stimulus is presented for, the faster the visual image decays in memory.
2. The duration of visible persistence is inversely related to stimulus luminance. When the luminance, or brightness of a stimulus is increased, the duration of visible persistence decreases. Due to the involvement of the neural system, visible persistence is highly dependent on the physiology of the photoreceptors and activation of different cell types in the visual cortex. This visible representation is subject to masking effects whereby the presentation of interfering stimulus during, or immediately after stimulus offset interferes with one's ability to remember the stimulus.

Different techniques have been used to attempt to identify the duration of visible persistence. The Duration of Stimulus Technique is one in which a probe stimulus (auditory "click") is presented simultaneously with the onset, and on a separate trial, with the offset of a visual display. The difference represents the duration of the visible store which was found to be approximately 100-200 ms. Alternatively, the Phenomenal Continuity and Moving Slit Technique estimated visible persistence to be 300 ms. In the first paradigm, an image is presented discontinuously with blank periods in between presentations. If the duration is short enough, the participant will perceive a continuous image. Similarly, the Moving Slit Technique is also based on the participant observing a continuous image. Only instead of flashing the entire stimulus on and off, only a very narrow portion or "slit" of the image is displayed. When the slit is oscillated at the correct speed, a complete image is viewed.

Neural basis

Underlying visible persistence is neural persistence of the visual sensory pathway. A prolonged visual representation begins with activation of photoreceptors in the retina. Although activation in both rods and cones has been found to persist beyond the physical offset of a stimulus, the rod system persists longer than cones. Other cells involved in a sustained visible image include M and P retinal ganglion cells. M cells (transient cells), are active only during stimulus onset and stimulus offset. P cells (sustained cells), show continuous activity during stimulus onset, duration, and offset. Cortical persistence of the visual image has been found in the primary visual cortex (V1) in the occipital lobe which is responsible for processing visual information.

Informational persistence

Information persistence represents the information about a stimulus that persists after its physical offset. It is visual in nature, but not visible. Sperling's experiments were a test of informational persistence. Stimulus duration is the key contributing factor to the duration of informational persistence. As stimulus duration increases, so does the duration of the visual code. The non-visual components represented by informational persistence include the abstract characteristics of the image, as well as its spatial location. Due to the nature of informational persistence, unlike visible persistence, it is immune to masking effects. The characteristics of this component of iconic memory suggest that it plays the key role in representing a post-categorical memory store for which VSTM can access information for consolidation.

The dorsal stream (green) and ventral stream (purple) are shown. They originate from a common source in visual cortex

Neural basis

Although less research exists regarding the neural representation of informational persistence compared to visible persistence, new electrophysiological techniques have begun to reveal cortical areas involved. Unlike visible persistence, informational persistence is thought to rely on higher-level visual areas beyond the visual cortex. The anterior superior temporal sulcus (STS), a part of the ventral stream, was found to be active in macaques during iconic memory tasks. This brain region is associated with object recognition and object identity. Iconic memory's role in change detection has been related to activation in the middle occipital gyrus (MOG). MOG activation was found to persist for approximately 2000ms suggesting a possibility that iconic memory has a longer duration than what was currently thought. Iconic memory is also influenced by genetics and proteins produced in the brain. Brain-derived neurotrophic factor (BDNF) is a part of the neurotrophin family of nerve growth factors. Individuals with mutations to the BDNF gene which codes for BDNF have been shown to have shortened, less stable informational persistence.

Role

Iconic memory provides a smooth stream of visual information to the brain which can be extracted over an extended period of time by VSTM for consolidation into more stable forms. One of iconic memory's key roles is involved with change detection of our visual environment which assists in the perception of motion.

Temporal integration

Iconic memory enables integrating visual information along a continuous stream of images, for example when watching a movie. In the primary visual cortex new stimuli do not erase information about previous stimuli. Instead the responses to the most recent stimulus contain about equal amounts of information about both this and the preceding stimulus. This one-back memory may be the main substrate for both the integration processes in iconic memory and masking effects. The particular outcome depends on whether the two subsequent component images (i.e., the "icons") are meaningful only when isolated (masking) or only when superimposed (integration).

Change blindness

The brief representation in iconic memory is thought to play a key role in the ability to detect change in a visual scene. The phenomenon of change blindness has provided insight into the nature of the iconic memory store and its role in vision. Change blindness refers to an inability to detect differences in two successive scenes separated by a very brief blank interval, or interstimulus interval (ISI). As such change blindness can be defined as being a slight lapse in iconic memory. When scenes are presented without an ISI, the change is easily detectable. It is thought that the detailed memory store of the scene in iconic memory is erased by each ISI, which renders the memory inaccessible. This reduces the ability to make comparisons between successive scenes.

Saccadic eye movement

It has been suggested that iconic memory plays a role in providing continuity of experience during saccadic eye movements. These rapid eye movements occur in approximately 30 ms and each fixation lasts for approximately 300 ms. Research suggests however, that memory for information between saccades is largely dependent on VSTM and not iconic memory. Instead of contributing to trans-saccadic memory, information stored in iconic memory is thought to actually be erased during saccades. A similar phenomenon occurs during eye-blinks whereby both automatic and intentional blinking disrupts the information stored in iconic memory.

Development

The development of iconic memory begins at birth and continues as development of the primary and secondary visual system occurs. By 6 months of age, infants' iconic memory capacity approaches adults'. By 5 years of age, children have developed the same unlimited capacity of iconic memory that adults possess. The duration of informational persistence however increases from approximately 200 ms at age 5, to an asymptotic level of 1000 ms as an adult (>11 years). A small decrease in visual persistence occurs with age. A decrease of approximately 20 ms has been observed when comparing individuals in their early 20s to those in their late 60s. Throughout one's lifetime, mild cognitive impairments (MCIs) may develop such as errors in episodic memory (autobiographical memory about people, places, and their contex), and working memory (the active processing component of STM) due to damage in hippocampal and association cortical areas. Episodic memories are autobiographical events that a person can discuss. Individuals with MCIs have been found to show decreased iconic memory capacity and duration. Iconic memory impairment in those with MCIs may be used as a predictor for the development of more severe deficits such as Alzheimer's disease and dementia later in life. Previous studies have shown that glucocorticoids have been closely linked to impact higher cognitive functioning. Glucocorticoid exposure causes severe memory retrieval impairment, explicitly advancing iconic memory decay. It reduces the active maintenance and storage of sensory information by altering transient neural responses during the initial stimulus processing stages.  Elevated cortisol levels have also been associated with faster iconic memory decay and top-down processing impairment, putting individuals at a higher risk of developing Dementia and AD. 

Iconic memory formation has been previously described as attention-free and fleeting, however newer studies have shown that in fact it does require attention. IM is shown to decay at a faster rate if attention focus is not appropriately met to the attention load. This allows for the information that is being transported into working memory to be retained more precisely.  Iconic memory decay has been found to occur at a rapid speed after the visual stimulus is no longer present. Without active retrieval, iconic memory averages to disappear within half a second. The theory of gradual decay in visual working memory claims that the accuracy at which the stimulus is remembered in iconic memory deteriorates over time. However, information stored in sensory memory is considered to facilitate exponential decay. 

Sperling's partial report procedure

In 1960, George Sperling became the first to use a partial report paradigm to investigate the bipartite model of VSTM. In Sperling's initial experiments in 1960, observers were presented with a tachistoscopic visual stimulus for a brief period of time (50 ms) consisting of either a 3x3 or 3x4 array of alphanumeric characters such as:

P Y F G

V J S A

D H B U

Recall was based on a cue which followed the offset of the stimulus and directed the subject to recall a specific line of letters from the initial display. Memory performance was compared under two conditions: whole report and partial report.

Whole report

Sperling's original partial report paradigm.

The whole report condition required participants to recall as many elements from the original display in their proper spatial locations as possible. Participants were typically able to recall three to five characters from the twelve character display (~35%). This suggests that whole report is limited by a memory system with a capacity of four-to-five items.

Partial report

The partial report condition required participants to identify a subset of the characters from the visual display using cued recall. The cue was a tone which sounded at various time intervals (~50 ms) following the offset of the stimulus. The frequency of the tone (high, medium, or low) indicated which set of characters within the display were to be reported. Due to the fact that participants did not know which row would be cued for recall, performance in the partial report condition can be regarded as a random sample of an observer's memory for the entire display. This type of sampling revealed that immediately after stimulus offset, participants could recall a given row (from a 3x3 grid of 9 letters) on 75% of trials, suggesting that 75% of the entire visual display (75% of 9-letters) was accessible to memory. This is a dramatic increase in the hypothesized capacity of iconic memory derived from full-report trials.

Variations of the partial report procedure

Averbach & Coriell's partial report paradigm.

Visual bar cue

A small variation in Sperling's partial report procedure which yielded similar results was the use of a visual bar marker instead of an auditory tone as the retrieval cue. In this modification, participants were presented with a visual display of 2 rows of 8 letters for 50 ms. The probe was a visual bar placed above or below a letter's position simultaneously with array offset. Participants had an average accuracy of 65% when asked to recall the designated letter.

Temporal variations

Varying the time between the offset of the display and the auditory cue allowed Sperling to estimate the time course of sensory memory. Sperling deviated from the original procedure by varying tone presentation from immediately after stimulus offset, to 150, 500, or 1000 ms. Using this technique, the initial memory for a stimulus display was found to decay rapidly after display offset. At approximately 1000 ms after stimulus offset, there was no difference in recall between the partial-report and whole report conditions. Overall, experiments using partial report provided evidence for a rapidly decaying sensory trace lasting approximately 1000 ms after the offset of a display.

Circle cue and masking

The effects of masking were identified by the use of a circle presented around a letter as the cue for recall. When the circle was presented before the visual stimulus onset or simultaneously with stimulus offset, recall matched that found when using a bar or tone. However, if a circle was used as a cue 100 ms after stimulus offset, there was decreased accuracy in recall. As the delay of circle presentation increased, accuracy once again improved. This phenomenon was an example of metacontrast masking. Masking was also observed when images such as random lines were presented immediately after stimulus offset.

Short-term memory

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Short-term_memory

Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recited. The duration of short-term memory (absent rehearsal or active maintenance) is estimated to be on the order of seconds. The commonly cited capacity of 7 items, found in Miller's Law, has been superseded by 4±1 items. In contrast, long-term memory holds information indefinitely.

Short-term memory is not the same as working memory, which refers to structures and processes used for temporarily storing and manipulating information.

Stores

The idea of separate memories for short-term and long-term storage originated in the 19th century. A model of memory developed in the 1960s assumed that all memories are formed in one store and transfer to others store after a small period of time. This model is referred to as the "modal model", most famously detailed by Shiffrin. The model states that memory is first stored in sensory memory, which has a large capacity but can only maintain information for milliseconds. A representation of that rapidly decaying memory is moved to short-term memory. Short-term memory does not have a large capacity like sensory memory, but holds information for seconds or minutes. The final storage is long-term memory, which has a very large capacity and is capable of holding information possibly for a lifetime.

The exact mechanisms by which this transfer takes place, whether all or only some memories are retained permanently, and even to have the existence of a genuine distinction between stores, remain controversial.

Evidence

Anterograde amnesia

One form of evidence cited in favor of the existence of a short-term store comes from anterograde amnesia, the inability to learn new facts and episodes. Patients with this form of amnesia have an intact ability to retain small amounts of information over short time scales (up to 30 seconds) but have little ability to form longer-term memories (illustrated by patient HM). This is interpreted as showing that the short-term store is spared from damage and diseases.

Distraction tasks

Other evidence comes from experimental studies showing that some manipulations impair memory for the 3 to 5 most recently learned words of a list (it is presumed that they are held in short-term memory). Recall for words from earlier in the list (it is presumed, stored in long-term memory) are unaffected. Other manipulations (e.g., semantic similarity of the words) affect only memory for earlier list words, but do not affect memory for the most recent few words. These results show that different factors affect short-term recall (disruption of rehearsal) and long-term recall (semantic similarity). Together, these findings show that long-term memory and short-term memory can vary independently of each other.

Models

Unitary model

Not all researchers agree that short- and long-term memory are separate systems. The alternative Unitary Model proposes that short-term memory consists of temporary activations of long term representations (that there is one memory that behaves variously over all time scales, from milliseconds to years). It has been difficult to identify a sharp boundary between short-term and long-term memory. For instance, Tarnow reported that the recall probability vs. latency curve is a straight line from 6 to 600 seconds, with the probability of failure to recall only saturating after 600 seconds. If two different stores were operating in this time domain, it is reasonable to expect a discontinuity in this curve. Other research has shown that the detailed pattern of recall errors looks remarkably similar to recall of a list immediately after learning (it is presumed, from short-term memory) and recall after 24 hours (necessarily from long-term memory).

Further evidence for a unified store comes from experiments involving continual distractor tasks. In 1974, Bjork and Whitten presented subjects with word pairs to remember; before and after each word pair, subjects performed a simple multiplication task for 12 seconds. After the final word-pair, subjects performed the multiplication distractor task for 20 seconds. They reported that the recency effect (the increased probability of recall of the last items studied) and the primacy effect (the increased probability of recall of the first few items) was sustained. These results are incompatible with a separate short-term memory as the distractor items should have displaced some of the word-pairs in the buffer, thereby weakening the associated strength of the items in long-term memory.

Tzeng (1973) reported an instance where the recency effect in free recall did not seem to result from a short-term memory store. Subjects were presented with four study-test periods of 10 word lists, with a continual distractor task (20-second period of counting-backward). At the end of each list, participants had to free-recall as many words as possible. After recall of the fourth list, participants were asked to recall items from all four lists. Both the initial and final recall showed a recency effect. These results violated the predictions of a short-term memory model, where no recency effect would be expected.

Koppenaal and Glanzer (1990) attempted to explain these phenomena as a result of the subjects' adaptation to the distractor task, which allowed them to preserve at least some short-term memory capabilities. In their experiment the long-term recency effect disappeared when the distractor after the last item differed from the distractors that preceded and followed the other items (e.g., arithmetic distractor task and word reading distractor task). Thapar and Greene challenged this theory. In one of their experiments, participants were given a different distractor task after every study item. According to Koppenaal and Glanzer's theory, no recency effect would be expected as subjects would not have had time to adapt to the distractor; yet such a recency effect remained in place in the experiment.

Another explanation

One proposed explanation for recency in a continual distractor condition, and its disappearance in an end-only distractor task is the influence of contextual and distinctive processes. According to this model, recency is a result of the similarity of the final items' processing context to the processing context of the other items and the distinctive position of the final items versus intermediate items. In the end distractor task, the processing context of the final items is no longer similar to that of the other list items. At the same time, retrieval cues for these items are no longer as effective as without the distractor. Therefore, recency recedes or vanishes. However, when distractor tasks are placed before and after each item, recency returns, because all the list items have similar processing context.

Synaptic theory

Various researchers have proposed that stimuli are coded in short-term memory using transmitter depletion. According to this hypothesis, a stimulus activates a spatial pattern of activity across neurons in a brain region. As these neurons fire, the available neurotransmitters are depleted. This depletion pattern represents stimulus information and functions as a memory trace. The memory trace decays over time as a consequence of neurotransmitter reuptake mechanisms that restore neurotransmitters to prior levels.

Relationship with working memory

The relationship between short-term memory and working memory is described by various theories, but the two concepts are generally considered distinct. Neither holds information for long, but short-term memory is a simple store, while working memory allows it to be manipulated. Short-term memory is part of working memory, but is not the same thing.

Working memory refers to structures and processes used for temporarily storing and manipulating information. Working memory has been termed working attention. Working memory and attention together play a major role in the thought process. Short-term memory in general refers to the short-term storage of information, and it does not encompass memory manipulation or organization. Thus, while short-term memory components appear in working memory models, the concept of short-term memory is distinct from other concepts.

Within Baddeley's influential 1986 model of working memory two short-term storage mechanisms appear: the phonological loop and the visuospatial sketchpad. Most of the above research involves the phonological loop, because most of the work on short-term memory uses verbal material. Since the 1990s, however, research on visual short-term memory and spatial short-term memory has expanded.

Duration

The limited duration of short-term memory (~18 seconds without rehearsal) suggests that its contents spontaneously decay over time. The decay assumption is part of many theories of short-term memory. The most notable one is Baddeley's model of working memory. The decay assumption is usually paired with the idea of rapid covert rehearsal: to retain information for longer, information must be periodically repeated or rehearsed, either by articulating it out loud or by mental simulation. Another type of rehearsal that can improve short-term memory is attention-based rehearsal. Information is mentally searched in a particular sequence. Once recalled, the information re-enters short-term memory and is then retained for a further period.

Nairn and Lewandosky et. al. dispute that spontaneous decay plays any significant role in short-term forgetting, and the evidence is not conclusive.

One alternative asserts that several elements (such as digits, words, or pictures, or logos) are held in short-term memory simultaneously, their representations compete with each other for recall, degrading each other. Thereby, new content gradually replaces older content, unless the older content is actively protected.

Capacity

Whatever the cause(s) of short-term forgetting, consensus asserts that it limits the amount of retained new information short term. This limit is referred to as the finite capacity of short-term memory. Short-term memory capacity is often called memory span, in reference to a common measurement procedure. In a memory span test, the experimenter presents a list of items (e.g. digits or words) of increasing length. An individual's span is determined as the longest list length that he or she can recall correctly in the given order on half or more trials.

In an early and influential article, "The Magical Number Seven, Plus or Minus Two", Miller suggested that human short-term memory has a forward memory span of approximately seven plus or minus two items and that that was well known at the time (apparently originating with Wundt). Later research reported that this "magical number seven" is roughly accurate for college students recalling lists of digits, but memory span varies widely across populations and material. For example, the ability to recall words in order depends on characteristics of those words: fewer words can be recalled when the words have longer spoken duration; this is known as the word-length effect, or when their speech sounds are similar to each other; this is called the phonological similarity effect. More words can be recalled when the words are highly familiar or occur frequently in speech. Recall performance is better when all of the words are taken from a single semantic category (such as games) than when the words are chosen randomly. A later estimate of short-term memory capacity reported that the capacity was about four pieces, or "chunks", of information. Other notable theories argue against measuring capacity in terms of the number of elements.

In the visual domain, several studies report no fixed capacity limit in terms of total number of items that can be retained. Instead, some investigators have argued for a limited resource that can be flexibly shared between items held in short-term memory, with some items (in the focus of attention) being allocated more resource and being recalled with greater fidelity. Many of these experiments have used delayed response tasks that have a continuous, analogue response space, rather than using a binary (correct/incorrect) recall method as is often used in change detection tasks. Instead of asking people to report whether a change occurred between the memory and probe array, delayed reproduction tasks require participants to reproduce the precise quality of a visual feature, e.g. an object’s orientation or colour.

Rehearsal

Rehearsal is the process of repeating information to be retained, ostensibly keeping it in short-term memory. Each repetition reenters the information into short-term memory, thus keeping that information for another 10 to 20 seconds (the average storage time for short-term memory).

Chunking

Chunking is a technique that allows memory to remember more things. Chunking involves organizing material into meaningful groups. Chunking can greatly increase recall capacity. For example, in recalling a phone number, chunking the digits into three groups (area code, prefix, and extension). This method of remembering phone numbers is far more effective than attempting to remember a string of 10 digits.

Practice and the usage of existing information in long-term memory can lead to additional improvements in chunking. In one testing session, an American cross-country runner was able to recall a string of 79 digits after hearing them only once by chunking them into groups the size of a running time.

Factors

Diseases that cause neurodegeneration, such as Alzheimer's disease, can damage short-term as well as long-term memory. Damage to certain sections of the brain due to this disease causes a shrinkage in the cerebral cortex, which impairs the ability to think and recall.

Short-term memory performance is influenced by diet. More intake of blueberries was reported to improve short-term memory after continuous use whereas alcohol decreases short-term memory performance.

Conditions

Age

Memory loss is a natural aging process. Research has reported short-term memory decreases with age. The decline appears to be constant and continuous beginning in the twenties.

One study used data from a previous study that compiled normative French data for three short-term memory tasks (verbal, visual and spatial). They found impairments in participants between the ages of 55 and 85 years of age.

Advanced age is also associated with decrements in episodic memory. The associated deficit is that differences in recognition memory reflect difficulty in binding components of a memory episode and bound units. A previous study used mixed and blocked test designs and reported an associative deficit for older adults.

Even absent neurological diseases and disorders, progressive and gradual loss of some intellectual functions become evident in later years. Several tests assess the psychophysical characteristics of the elderly, such as the functional reach (FR) test and the mini–mental state examination (MMSE). FR is an index of the aptitude to maintain balance in an upright position, while the MMSE test is a global index of cognitive abilities. These tests were used by Costarella et al. to evaluate the psychophysical characteristics of older adults. They found a loss of physical performance (FR, related to height) as well as a loss of cognitive abilities (MMSE).

Alzheimer's disease

Memory distortion in Alzheimer's disease is a disorder common in older adults. One study compared patients with mild to moderate Alzheimer's disease versus age matched healthy adults. Alzheimer's patients had more severely reduced short-term memory. Visual short-term memory is also impaired in sporadic, late-onset as well as familial Alzheimer’s disease, when assessed using delayed reproduction tasks. These studies point to a deficit in visual feature binding as an important component of the deficit. Episodic memory and semantic abilities deteriorate early in Alzheimer's disease. Since the cognitive system includes interconnected and reciprocally influenced neuronal networks, one study hypothesized that stimulation of lexical-semantic abilities may benefit semantically structured episodic memory. They found that Lexical-Semantic stimulation treatment could improve episodic memory.

Aphasia

Aphasias commonly occur after left-hemisphere stroke or with neurodegenerative conditions such as primary progressive aphasias. Patients with left temporoparietal focal lesions may suffer a deficit of verbal short-term memory, which may also be a feature of logopenic primary progressive aphasia.

Many language-impaired patients complain about short-term memory deficits. Family members confirm that patients have trouble recalling previously known names and events. These signals are supported by studies reporting that many aphasics also have trouble with visual-memory required tasks. There have been reports of deficits in verbal short-term memory when related to short term memory, these deficits are harder to treat since their are less measurements for verbal short term memory.

Schizophrenia

Core symptoms of schizophrenia patients have been linked to cognitive deficits. One neglected factor that contributes to those deficits is the comprehension of time. Schizophrenics are not able to process how much time has passed. They are unable to process this because they have impaired temporal information processing. They can't tell what the actual time is, what day of the week it is, what month it is, or what year it is. For some, they feel as though time is either sped up or slowed down. This causes them to have instability in life. Not being able to tell time or know what year they are in, forces them to not be able to have a stable life. Schizophrenics have the inability to detect rhythm irregularities and estimating durations of time. This affects the verbal and psychical abilities. They have a harder time making judgments between multiple events because it is all bound together as one for them.

Post-traumatic stress disorder

Posttraumatic stress disorder (PTSD) is associated with altered processing of emotional material with strong attentional bias toward trauma-related information. It interferes with cognitive processing. Aside from trauma processing specificities, a range of cognitive impairments have been associated with PTSD state, including attention and verbal memory deficits.

Intelligence

Few studies have been done on the relationship between short-term memory and intelligence. One study examined whether people with PTSD had equivalent levels of short-term, non-verbal memory on the Benton Visual Retention Test (BVRT), and whether they had equivalent levels of intelligence on the Raven Standard Progressive Matrices (RSPM). They found that people with PTSD had worse short-term, non-verbal memory on the BVRT, despite having comparable levels of intelligence on the RSPM, concluding impairments in memory influence intelligence assessments in the subjects.

Short-term memory in literature and popular culture

• "The Last Hippie" in An Anthropologist on Mars, a medical case history in a book by British neurologist Oliver Sacks.
• 50 First Dates, a film
• Ghajini, a film
• Memento, a film
• "Ænema", Tool