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A mental image is an experience that, on most occasions, significantly resembles the experience of 'perceiving' some object, event, or scene, but occurs when the relevant object, event, or scene is not actually present to the senses. There are sometimes episodes, particularly on falling asleep ( hypnagogic imagery) and waking up ( hypnopompic imagery), when the mental imagery may be dynamic, phantasmagoric and involuntary in character, repeatedly presenting identifiable objects or actions, spilling over from waking events, or defying perception, presenting a kaleidoscopic field, in which no distinct object can be discerned. Mental imagery can sometimes produce the same effects as would be produced by the behavior or experience imagined. The nature of these experiences, what makes them possible, and their function (if any) have long been subjects of research and controversy in philosophy,
psychology Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries between ...
, cognitive science, and, more recently,
neuroscience Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, developme ...
. As contemporary researchers use the expression, mental images or imagery can comprise information from any source of sensory input; one may experience auditory images, olfactory images, and so forth. However, the majority of philosophical and scientific investigations of the topic focus upon ''visual'' mental imagery. It has sometimes been assumed that, like humans, some types of animals are capable of experiencing mental images. Due to the fundamentally introspective nature of the phenomenon, it has been difficult to assess whether or not non-human animals experience mental imagery. Philosophers such as George Berkeley and
David Hume David Hume (; born David Home; 7 May 1711 NS (26 April 1711 OS) – 25 August 1776) Cranston, Maurice, and Thomas Edmund Jessop. 2020 999br>David Hume" ''Encyclopædia Britannica''. Retrieved 18 May 2020. was a Scottish Enlightenment phil ...
, and early experimental psychologists such as Wilhelm Wundt and
William James William James (January 11, 1842 – August 26, 1910) was an American philosopher, historian, and psychologist, and the first educator to offer a psychology course in the United States. James is considered to be a leading thinker of the lat ...
, understood
idea In common usage and in philosophy, ideas are the results of thought. Also in philosophy, ideas can also be mental representational images of some object. Many philosophers have considered ideas to be a fundamental ontological category of bei ...
s in general to be mental images. Today it is very widely believed that much imagery functions as mental representations (or
mental model A mental model is an explanation of someone's thought process about how something works in the real world. It is a representation of the surrounding world, the relationships between its various parts and a person's intuitive perception about thei ...
s), playing an important role in memory and thinking. William Brant (2013, p. 12) traces the scientific use of the phrase "mental images" back to John Tyndall's 1870 speech called the "Scientific Use of the Imagination". Some have suggested that images are best understood to be, by definition, a form of inner, mental or neural representation. Others reject the view that the image experience may be identical with (or directly caused by) any such representation in the mind or the brain, but do not take account of the non-representational forms of imagery.


Mind's eye

The notion of a "mind's eye" goes back at least to
Cicero Marcus Tullius Cicero ( ; ; 3 January 106 BC – 7 December 43 BC) was a Roman statesman, lawyer, scholar, philosopher, and academic skeptic, who tried to uphold optimate principles during the political crises that led to the esta ...
's reference to ''mentis oculi'' during his discussion of the orator's appropriate use of
simile A simile () is a figure of speech that directly ''compares'' two things. Similes differ from other metaphors by highlighting the similarities between two things using comparison words such as "like", "as", "so", or "than", while other metaphors c ...
. In this discussion, Cicero observed that allusions to "the Syrtis of his patrimony" and "the Charybdis of his possessions" involved similes that were "too far-fetched"; and he advised the orator to, instead, just speak of "the rock" and "the gulf" (respectively)—on the grounds that "the eyes of the mind are more easily directed to those objects which we have seen, than to those which we have only heard". The concept of "the mind's eye" first appeared in English in Chaucer's (c. 1387) Man of Law's Tale in his ''
Canterbury Tales ''The Canterbury Tales'' ( enm, Tales of Caunterbury) is a collection of twenty-four stories that runs to over 17,000 lines written in Middle English by Geoffrey Chaucer between 1387 and 1400. It is widely regarded as Chaucer's ''magnum opus ...
'', where he tells us that one of the three men dwelling in a castle was blind, and could only see with "the eyes of his mind"; namely, those eyes "with which all men see after they have become blind".


Physical basis

The biological foundation of mental imagery is not fully understood. Studies using
fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area ...
have shown that the
lateral geniculate nucleus In neuroanatomy, the lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projec ...
and the V1 area of the
visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
are activated during mental imagery tasks. Ratey writes:
The visual pathway is not a one-way street. Higher areas of the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ve ...
can also send visual input back to
neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...
s in lower areas of the visual cortex. ..As humans, we have the ability to see with the mind's eye—to have a perceptual experience in the absence of visual input. For example,
PET scan Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, ...
s have shown that when subjects, seated in a room, imagine they are at their front door starting to walk either to the left or right, activation begins in the
visual association cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
, the parietal cortex, and the
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46 ...
—all higher cognitive processing centers of the brain.
A biological basis for mental imagery is found in the deeper portions of the brain below the neocortex. In a large study with 285 participants, Tabi, Maio, Attaallah, et al. (2022) investigated the association between an established measure of visual mental imagery,
Vividness of Visual Imagery Questionnaire The Vividness of Visual Imagery Questionnaire (VVIQ) was developed in 1973 by the British psychologist David Marks (Marks, 1973). The VVIQ consists of 16 items in four groups of 4 items in which the participant is invited to consider the mental im ...
(VVIQ) scores, and volumes of brain structures including the
hippocampus The hippocampus (via Latin from Greek , ' seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, ...
,
amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verte ...
, primary motor cortex,
primary visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
and the
fusiform gyrus The fusiform gyrus, also known as the ''lateral occipitotemporal gyrus'','' ''is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and th ...
. Tabi et al. (2022) found significant positive correlations between visual imagery vividness and the volumes of the hippocampus and primary visual cortex. Significant positive correlations were also obtained between VVIQ scores and hippocampal structures including Bilateral CA1, CA3, CA4 and Granule Cell (GC) and Molecular Layer (ML) of the Dentate Gyrus (DG). Follow-up analysis revealed that visual imagery was in particular correlated with the four subfields presented in the above illustration (Tabi et al., 2022). The
thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...
has been found to be discrete to other components in that it processes all forms of perceptional data relayed from both lower and higher components of the brain. Damage to this component can produce permanent perceptual damage, however when damage is inflicted upon the
cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...
, the brain adapts to
neuroplasticity Neuroplasticity, also known as neural plasticity, or brain plasticity, is the ability of neural networks in the brain to change through growth and reorganization. It is when the brain is rewired to function in some way that differs from how it p ...
to amend any occlusions for perception . It can be thought that the neocortex is a sophisticated memory storage warehouse in which data received as an input from sensory systems are compartmentalized via the cerebral cortex. This would essentially allow for shapes to be identified, although given the lack of filtering input produced internally, one may as a consequence, hallucinate—essentially seeing something that isn't received as an input externally but rather internal (i.e. an error in the filtering of segmented sensory data from the cerebral cortex may result in one seeing, feeling, hearing or experiencing something that is inconsistent with reality). Not all people have the same mental imagery ability. For many, when the eyes are closed, the perception of darkness prevails. However, some people are able to perceive colorful, dynamic imagery (McKellar, 1957). The use of
hallucinogen Hallucinogens are a large, diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mood, and perception as well as other changes. Most hallucinogens can be categorize ...
ic drugs increases the subject's ability to consciously access mental imagery including synaestesia (McKellar, 1957). Furthermore, the pineal gland is a hypothetical candidate for producing a mind's eye. Rick Strassman and others have postulated that during
near-death experiences A near-death experience (NDE) is a profound personal experience associated with death or impending death which researchers claim share similar characteristics. When positive, such experiences may encompass a variety of sensations including detac ...
(NDEs) and dreaming, the gland might secrete a hallucinogenic chemical ''N'',''N''-Dimethyltryptamine (DMT) to produce internal visuals when external sensory data is occluded. However, this hypothesis has yet to be fully supported with
neurochemical A neurochemical is a small organic molecule or peptide that participates in neural activity. The science of neurochemistry studies the functions of neurochemicals. Prominent neurochemicals Neurotransmitters and neuromodulators *Glutamate is the ...
evidence and plausible mechanism for DMT production. The condition where a person lacks mental imagery is called
aphantasia Aphantasia ( , ) is the inability to create mental imagery. The phenomenon was first described by Francis Galton in 1880 but has since remained relatively unstudied. Interest in the phenomenon renewed after the publication of a study in 2015 ...
. The term was first suggested in a 2015 study. Common examples of mental images include
daydreaming Daydreaming is the stream of consciousness that detaches from current, external tasks when attention drifts to a more personal and internal direction. This phenomenon is common in people's daily life shown by a large-scale study in which partici ...
and the mental visualization that occurs while reading a book. Another is of the pictures summoned by athletes during training or before a competition, outlining each step they will take to accomplish their goal. When a musician hears a song, they can sometimes "see" the song notes in their head, as well as hear them with all their tonal qualities. This is considered different from an after-effect, such as an
afterimage AfterImage is a Filipino rock band formed in 1986, best known for their songs "Habang May Buhay", "Next in Line", and "Mangarap Ka". They disbanded in 1997 and became active again in 2008 after they reunited and released their fourth studio alb ...
. Calling up an image in our minds can be a voluntary act, so it can be characterized as being under various degrees of conscious control. There are several theories as to how mental images are formed in the mind. These include the dual-code theory, the propositional theory, and the functional-equivalency hypothesis. The dual-code theory, created by
Allan Paivio Allan Urho Paivio (March 29, 1925 – June 19, 2016) was a professor of psychology at the University of Western Ontario and former bodybuilder. He earned his Ph.D. from McGill University in 1959 and taught at the University of Western Ontario ...
in 1971, is the theory that we use two separate codes to represent information in our brains: image codes and verbal codes. Image codes are things like thinking of a picture of a dog when you are thinking of a dog, whereas a verbal code would be to think of the word "dog". Another example is the difference between thinking of abstract words such as ''justice'' or ''love'' and thinking of concrete words like ''elephant'' or ''chair.'' When abstract words are thought of, it is easier to think of them in terms of verbal codes—finding words that define them or describe them. With concrete words, it is often easier to use image codes and bring up a picture of a ''human'' or ''chair'' in your mind rather than words associated or descriptive of them. The propositional theory involves storing images in the form of a generic propositional code that stores the meaning of the concept not the image itself. The propositional codes can either be descriptive of the image or symbolic. They are then transferred back into verbal and visual code to form the mental image. The functional-equivalency hypothesis is that mental images are "internal representations" that work in the same way as the actual perception of physical objects. In other words, the picture of a dog brought to mind when the word ''dog'' is read is interpreted in the same way as if the person looking at an actual dog before them. Research has occurred to designate a specific neural correlate of imagery; however, studies show a multitude of results. Most studies published before 2001 suggest neural correlates of visual imagery occur in
Brodmann area 17 The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
. Auditory performance imagery have been observed in the premotor areas, precunes, and medial
Brodmann area 40 Brodmann area 40 (BA40) is part of the parietal cortex in the human brain. The inferior part of BA40 is in the area of the supramarginal gyrus, which lies at the posterior end of the lateral fissure, in the inferior lateral part of the parieta ...
. Auditory imagery in general occurs across participants in the temporal voice area (TVA), which allows top-down imaging manipulations, processing, and storage of audition functions. Olfactory imagery research shows activation in the anterior piriform cortex and the posterior piriform cortex; experts in olfactory imagery have larger gray matter associated to olfactory areas. Tactile imagery is found to occur in the dorsolateral prefrontal area, inferior frontal gyrus, frontal gyrus, insula, precentral gyrus, and the medial frontal gyrus with basal ganglia activation in the ventral posteriomedial nucleus and putamen (hemisphere activation corresponds to the location of the imagined tactile stimulus). Research in gustatory imagery reveals activation in the anterior insular cortex, frontal operculum, and prefrontal cortex. Novices of a specific form of mental imagery show less gray matter than experts of mental imagery congruent to that form. A meta-analysis of neuroimagery studies revealed significant activation of the bilateral dorsal parietal, interior insula, and left inferior frontal regions of the brain. Causal evidence from neurological patients with brain lesions demonstrates that vivid visual mental imagery is possible even when occipital visual areas are lesioned or disconnected from more anterior cortex. Visual mental imagery can instead be impaired by left temporal damage. Consistent with these findings, a meta-analysis of 27 neuroimaging studies demonstrated imagery-related activity in a region of the left ventral temporal cortex, which was dubbed the Fusiform Imagery Node.. An additional Bayesian analysis excluded a role for occipital cortex in visual mental imagery, consistent with the evidence from neurological patients. Imagery has been thought to cooccur with perception; however, participants with damaged sense-modality receptors can sometimes perform imagery of said modality receptors. Neuroscience with imagery has been used to communicate with seemingly unconscious individuals through fMRI activation of different neural correlates of imagery, demanding further study into low quality consciousness. A study on one patient with one
occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...
removed found the horizontal area of their visual mental image was reduced.


Neural substrates of visual imagery

Visual imagery is the ability to create mental representations of things, people, and places that are absent from an individual’s visual field. This ability is crucial to problem-solving tasks, memory, and spatial reasoning.Dijkstra, N., Bosch, S. E., & van Gerven, M. A. J
“Vividness of Visual Imagery Depends on the Neural Overlap with Perception in Visual Areas”
, The Journal of Neuroscience, 37(5), 1367 LP-1373. (2017).
Neuroscientist A neuroscientist (or neurobiologist) is a scientist who has specialised knowledge in neuroscience, a branch of biology that deals with the physiology, biochemistry, psychology, anatomy and molecular biology of neurons, neural circuits, and glial ...
s have found that imagery and
perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
share many of the same
neural substrate A neural substrate is a term used in neuroscience to indicate the part of the central nervous system (i.e., brain and spinal cord) that underlies a specific behavior, cognitive process, or psychological state. ''Neural'' is an adjective relating ...
s, or areas of the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ve ...
that function similarly during both imagery and perception, such as the
visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
and higher visual areas. Kosslyn and colleagues (1999) showed that the early visual cortex, Area 17 and Area 18/19, is activated during visual imagery. They found that inhibition of these areas through repetitive
transcranial magnetic stimulation Transcranial magnetic stimulation (TMS) is a noninvasive form of brain stimulation in which a changing magnetic field is used to induce an electric current at a specific area of the brain through electromagnetic induction. An electric pulse gener ...
(rTMS) resulted in impaired visual perception and imagery. Furthermore, research conducted with lesioned patients has revealed that visual imagery and visual perception have the same representational organization. This has been concluded from patients in which impaired perception also experience visual imagery deficits at the same level of the mental representation. Behrmann and colleagues (1992) describe a patient C.K., who provided evidence challenging the view that visual imagery and visual perception rely on the same representational system. C.K. was a 33-year old man with visual object agnosia acquired after a vehicular accident. This deficit prevented him from being able to recognize objects and copy objects fluidly. Surprisingly, his ability to draw accurate objects from memory indicated his visual imagery was intact and normal. Furthermore, C.K. successfully performed other tasks requiring visual imagery for judgment of size, shape, color, and composition. These findings conflict with previous research as they suggest there is a partial dissociation between visual imagery and visual perception. C.K. exhibited a perceptual deficit that was not associated with a corresponding deficit in visual imagery, indicating that these two processes have systems for mental representations that may not be mediated entirely by the same neural substrates. Schlegel and colleagues (2013) conducted a
functional MRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...
analysis of regions activated during manipulation of visual imagery. They identified 11 bilateral cortical and subcortical regions that exhibited increased activation when manipulating a visual image compared to when the visual image was just maintained. These regions included the
occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...
and
ventral stream The two-streams hypothesis is a model of the neural processing of vision as well as hearing. The hypothesis, given its initial characterisation in a paper by David Milner and Melvyn A. Goodale in 1992, argues that humans possess two distinct vis ...
areas, two
parietal lobe The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...
regions, the
posterior parietal cortex The posterior parietal cortex (the portion of parietal neocortex posterior to the primary somatosensory cortex) plays an important role in planned movements, spatial reasoning, and attention. Damage to the posterior parietal cortex can produce a ...
and the
precuneus In neuroanatomy, the precuneus is the portion of the superior parietal lobule on the medial surface of each brain hemisphere. It is located in front of the cuneus (the upper portion of the occipital lobe). The precuneus is bounded in front by th ...
lobule, and three
frontal lobe The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove be ...
regions, the frontal eye fields, dorsolateral prefrontal cortex, and the
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46 ...
. Due to their suspected involvement in
working memory Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...
and attention, the authors propose that these parietal and prefrontal regions, and occipital regions, are part of a network involved in mediating the manipulation of visual imagery. These results suggest a top-down activation of visual areas in visual imagery. Using Dynamic Causal Modeling (DCM) to determine the connectivity of cortical networks, Ishai et al. (2010) demonstrated that activation of the network mediating visual imagery is initiated by prefrontal cortex and posterior parietal cortex activity. Generation of objects from memory resulted in initial activation of the prefrontal and the posterior parietal areas, which then activate earlier visual areas through backward connectivity. Activation of the prefrontal cortex and posterior parietal cortex has also been found to be involved in retrieval of object representations from
long-term memory Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to short-term and working memory, which persist for only about 18 to 30 seconds. Long- ...
, their maintenance in working memory, and attention during visual imagery. Thus, Ishai et al. suggest that the network mediating visual imagery is composed of attentional mechanisms arising from the posterior parietal cortex and the prefrontal cortex. Vividness of visual imagery is a crucial component of an individual’s ability to perform cognitive tasks requiring imagery. Vividness of visual imagery varies not only between individuals but also within individuals. Dijkstra and colleagues (2017) found that the variation in vividness of visual imagery is dependent on the degree to which the neural substrates of visual imagery overlap with those of visual perception. They found that overlap between imagery and perception in the entire visual cortex, the parietal precuneus lobule, the right parietal cortex, and the medial frontal cortex predicted the vividness of a mental representation. The activated regions beyond the visual areas are believed to drive the imagery-specific processes rather than the visual processes shared with perception. It has been suggested that the precuneus contributes to vividness by selecting important details for imagery. The medial frontal cortex is suspected to be involved in the retrieval and integration of information from the parietal and visual areas during working memory and visual imagery. The right parietal cortex appears to be important in attention, visual inspection, and stabilization of mental representations. Thus, the neural substrates of visual imagery and perception overlap in areas beyond the visual cortex and the degree of this overlap in these areas correlates with the vividness of mental representations during imagery.


Philosophical ideas

Mental images are an important topic in classical and modern philosophy, as they are central to the study of
knowledge Knowledge can be defined as Descriptive knowledge, awareness of facts or as Procedural knowledge, practical skills, and may also refer to Knowledge by acquaintance, familiarity with objects or situations. Knowledge of facts, also called pro ...
. In the '' Republic'', Book VII,
Plato Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was a Greek philosopher born in Athens during the Classical period in Ancient Greece. He founded the Platonist school of thought and the Academy, the first institution ...
has
Socrates Socrates (; ; –399 BC) was a Greek philosopher from Athens who is credited as the founder of Western philosophy and among the first moral philosophers of the ethical tradition of thought. An enigmatic figure, Socrates authored no te ...
present the
Allegory of the Cave The Allegory of the Cave, or Plato's Cave, is an allegory presented by the Greek philosopher Plato in his work ''Republic'' (514a–520a) to compare "the effect of education ( παιδεία) and the lack of it on our nature". It is written as ...
: a prisoner, bound and unable to move, sits with his back to a fire watching the shadows cast on the cave wall in front of him by people carrying objects behind his back. These people and the objects they carry are representations of real things in the world. Unenlightened man is like the prisoner, explains Socrates, a human being making mental images from the sense data that he experiences. The eighteenth-century philosopher Bishop George Berkeley proposed similar ideas in his theory of
idealism In philosophy, the term idealism identifies and describes metaphysical perspectives which assert that reality is indistinguishable and inseparable from perception and understanding; that reality is a mental construct closely connected t ...
. Berkeley stated that reality is equivalent to mental images—our mental images are not a copy of another material reality but that reality itself. Berkeley, however, sharply distinguished between the images that he considered to constitute the external world, and the images of individual imagination. According to Berkeley, only the latter are considered "mental imagery" in the contemporary sense of the term. The eighteenth century British writer Dr. Samuel Johnson criticized idealism. When asked what he thought about idealism, he is alleged to have replied "I refute it thus!" as he kicked a large rock and his leg rebounded. His point was that the idea that the rock is just another mental image and has no material existence of its own is a poor explanation of the painful sense data he had just experienced. David Deutsch addresses Johnson's objection to idealism in ''The Fabric of Reality'' when he states that, if we judge the value of our mental images of the world by the quality and quantity of the sense data that they can explain, then the most valuable mental image—or theory—that we currently have is that the world has a real independent existence and that humans have successfully evolved by building up and adapting patterns of mental images to explain it. This is an important idea in scientific thought. Critics of
scientific realism Scientific realism is the view that the universe described by science is real regardless of how it may be interpreted. Within philosophy of science, this view is often an answer to the question "how is the success of science to be explained?" Th ...
ask how the inner perception of mental images actually occurs. This is sometimes called the "
homunculus A homunculus ( , , ; "little person") is a representation of a small human being, originally depicted as small statues made out of clay. Popularized in sixteenth-century alchemy and nineteenth-century fiction, it has historically referred to the ...
problem" (see also the mind's eye). The problem is similar to asking how the images you see on a computer screen exist in the memory of the computer. To scientific materialism, mental images and the perception of them must be brain-states. According to critics, scientific realists cannot explain where the images and their perceiver exist in the brain. To use the analogy of the computer screen, these critics argue that cognitive science and
psychology Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries between ...
have been unsuccessful in identifying either the component in the brain (i.e., "hardware") or the mental processes that store these images (i.e. "software").


In experimental psychology

Cognitive psychologists and (later) cognitive neuroscientists have empirically tested some of the philosophical questions related to whether and how the human brain uses mental imagery in cognition.
right Rights are legal, social, or ethical principles of freedom or entitlement; that is, rights are the fundamental normative rules about what is allowed of people or owed to people according to some legal system, social convention, or ethical ...
One theory of the mind that was examined in these experiments was the "brain as serial computer" philosophical metaphor of the 1970s. Psychologist
Zenon Pylyshyn Zenon Walter Pylyshyn (; 25 August 1937–6 December 2022) was a Canadian cognitive scientist and philosopher. He was a Canada Council Senior Fellow from 1963 to 1964. Pylyshyn's research generally involved the theoretical analysis of the nat ...
theorized that the human mind processes mental images by decomposing them into an underlying mathematical proposition.
Roger Shepard Roger Newland Shepard (January 30, 1929 – May 30, 2022) was an American cognitive scientist and author of the "universal law of generalization" (1987). He was considered a father of research on spatial relations. He studied mental rotation, an ...
and Jacqueline Metzler challenged that view by presenting subjects with 2D line drawings of groups of 3D block "objects" and asking them to determine whether that "object" is the same as a second figure, some of which rotations of the first "object". Shepard and Metzler proposed that if we decomposed and then mentally re-imaged the objects into basic mathematical propositions, as the then-dominant view of cognition "as a serial digital computer" assumed, then it would be expected that the time it took to determine whether the object is the same or not would be independent of how much the object had been rotated. Shepard and Metzler found the opposite: a linear relationship between the degree of rotation in the mental imagery task and the time it took participants to reach their answer. This
mental rotation Mental rotation is the ability to rotate mental representations of two-dimensional and three-dimensional objects as it is related to the visual representation of such rotation within the human mind. There is a relationship between areas of the bra ...
finding implied that the human mind—and the human brain—maintains and manipulates mental images as topographic and topological wholes, an implication that was quickly put to test by psychologists.
Stephen Kosslyn Stephen Michael Kosslyn (born 1948) is an American psychologist and neuroscientist. Kosslyn is best known for his work on visual cognition and the science of learning. Kosslyn currently serves as the president of Active Learning Sciences Inc., w ...
and colleagues showed in a series of neuroimaging experiments that the mental image of objects like the letter "F" are mapped, maintained and rotated as an image-like whole in areas of the human visual cortex. Moreover, Kosslyn's work showed that there are considerable similarities between the neural mappings for imagined stimuli and perceived stimuli. The authors of these studies concluded that, while the neural processes they studied rely on mathematical and computational underpinnings, the brain also seems optimized to handle the sort of mathematics that constantly computes a series of topologically-based images rather than calculating a mathematical model of an object. Recent studies in neurology and neuropsychology on mental imagery have further questioned the "mind as serial computer" theory, arguing instead that human mental imagery manifests both visually and kinesthetically. For example, several studies have provided evidence that people are slower at rotating line drawings of objects such as hands in directions incompatible with the joints of the human body, and that patients with painful, injured arms are slower at mentally rotating line drawings of the hand from the side of the injured arm. Some psychologists, including Kosslyn, have argued that such results occur because of interference in the brain between distinct systems in the brain that process the visual and motor mental imagery. Subsequent
neuroimaging Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incr ...
studies showed that the interference between the motor and visual imagery system could be induced by having participants physically handle actual 3D blocks glued together to form objects similar to those depicted in the line-drawings. Amorim et al. have shown that, when a cylindrical "head" was added to Shepard and Metzler's line drawings of 3D block figures, participants were quicker and more accurate at solving mental rotation problems. They argue that motoric embodiment is not just "interference" that inhibits visual mental imagery but is capable of facilitating mental imagery. As cognitive neuroscience approaches to mental imagery continued, research expanded beyond questions of serial versus parallel or topographic processing to questions of the relationship between mental images and perceptual representations. Both brain imaging (fMRI and ERP) and studies of neuropsychological patients have been used to test the hypothesis that a mental image is the reactivation, from memory, of brain representations normally activated during the perception of an external stimulus. In other words, if perceiving an apple activates contour and location and shape and color representations in the brain’s visual system, then imagining an apple activates some or all of these same representations using information stored in memory. Early evidence for this idea came from neuropsychology. Patients with brain damage that impairs perception in specific ways, for example by damaging shape or color representations, seem to generally to have impaired mental imagery in similar ways. Studies of brain function in normal human brains support this same conclusion, showing activity in the brain’s visual areas while subjects imagined visual objects and scenes. The previously mentioned and numerous related studies have led to a relative consensus within cognitive science, psychology, neuroscience, and philosophy on the neural status of mental images. In general, researchers agree that, while there is no
homunculus A homunculus ( , , ; "little person") is a representation of a small human being, originally depicted as small statues made out of clay. Popularized in sixteenth-century alchemy and nineteenth-century fiction, it has historically referred to the ...
inside the head viewing these mental images, our brains do form and maintain mental images as image-like wholes. The problem of exactly how these images are stored and manipulated within the human brain, in particular within language and communication, remains a fertile area of study. One of the longest-running research topics on the mental image has basis on the fact that people report large individual differences in the vividness of their images. Special questionnaires have been developed to assess such differences, including the Vividness of Visual Imagery Questionnaire (VVIQ) developed by
David Marks David Lee Marks (born August 22, 1948) is an American guitarist who is best known for being an early member of the Beach Boys. While growing up in Hawthorne, California, Marks was a neighborhood friend of the original band members and was a freq ...
. Laboratory studies have suggested that the subjectively reported variations in imagery vividness are associated with different neural states within the brain and also different cognitive competences such as the ability to accurately recall information presented in pictures Rodway, Gillies and Schepman used a novel long-term change detection task to determine whether participants with low and high vividness scores on the VVIQ2 showed any performance differences. Rodway et al. found that high vividness participants were significantly more accurate at detecting salient changes to pictures compared to low-vividness participants. This replicated an earlier study. Recent studies have found that individual differences in VVIQ scores can be used to predict changes in a person's brain while visualizing different activities. Functional magnetic resonance imaging (fMRI) was used to study the association between early visual cortex activity relative to the whole brain while participants visualized themselves or another person bench pressing or stair climbing. Reported image vividness correlates significantly with the relative fMRI signal in the visual cortex. Thus, individual differences in the vividness of visual imagery can be measured objectively. Logie, Pernet, Buonocore and Della Sala (2011) used behavioural and fMRI data for mental rotation from individuals reporting vivid and poor imagery on the VVIQ. Groups differed in brain activation patterns suggesting that the groups performed the same tasks in different ways. These findings help to explain the lack of association previously reported between VVIQ scores and mental rotation performance.


Training and learning styles

Some educational theorists have drawn from the idea of mental imagery in their studies of
learning styles Learning styles refer to a range of theories that aim to account for differences in individuals' learning. Although there is ample evidence that individuals express personal preferences for how they prefer to receive information, few studies have ...
. Proponents of these theories state that people often have learning processes that emphasize visual, auditory, and kinesthetic systems of experience. According to these theorists, teaching in multiple overlapping sensory systems benefits learning, and they encourage teachers to use content and media that integrates well with the visual, auditory, and kinesthetic systems whenever possible. Educational researchers have examined whether the experience of mental imagery affects the degree of learning. For example, imagining playing a five-finger piano exercise (mental practice) resulted in a significant improvement in performance over no mental practice—though not as significant as that produced by physical practice. The authors of the study stated that "mental practice alone seems to be sufficient to promote the modulation of neural circuits involved in the early stages of motor skill learning".


Visualization and the Himalayan traditions

In general,
Vajrayana Vajrayāna ( sa, वज्रयान, "thunderbolt vehicle", "diamond vehicle", or "indestructible vehicle"), along with Mantrayāna, Guhyamantrayāna, Tantrayāna, Secret Mantra, Tantric Buddhism, and Esoteric Buddhism, are names referring t ...
Buddhism Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religions, Indian religion or Indian philosophy#Buddhist philosophy, philosophical tradition based on Pre-sectarian Buddhism, teachings attributed to the Buddha. ...
, Bön, and
Tantra Tantra (; sa, तन्त्र, lit=loom, weave, warp) are the esoteric traditions of Hinduism and Buddhism that developed on the Indian subcontinent from the middle of the 1st millennium CE onwards. The term ''tantra'', in the Indian ...
utilize sophisticated visualization or ''imaginal'' (in the language of
Jean Houston Jean Houston (born 10 May 1937) is an American author involved in the human potential movement. Along with her husband, Robert Masters, she co-founded the Foundation for Mind Research. Biography Early life and education Houston was born in New ...
of
Transpersonal Psychology Transpersonal psychology, or spiritual psychology, is a sub-field or school of psychology that integrates the spiritual and transcendent aspects of the human experience with the framework of modern psychology. The '' transpersonal'' is defined ...
) processes in the thoughtform construction of the
yidam ''Yidam'' is a type of deity associated with tantric or Vajrayana Buddhism said to be manifestations of Buddhahood or enlightened mind. During personal meditation (''sādhana'') practice, the yogi identifies their own form, attributes and mi ...
sadhana, kye-rim, and dzog-rim modes of
meditation Meditation is a practice in which an individual uses a technique – such as mindfulness, or focusing the mind on a particular object, thought, or activity – to train attention and awareness, and achieve a mentally clear and emotionally calm ...
and in the
yantra Yantra () (literally "machine, contraption") is a geometrical diagram, mainly from the Tantric traditions of the Indian religions. Yantras are used for the worship of deities in temples or at home; as an aid in meditation; used for the benefit ...
,
thangka A ''thangka'', variously spelled as ''thangka'', ''tangka'', ''thanka'', or ''tanka'' (; Tibetan: ཐང་ཀ་; Nepal Bhasa: पौभा), is a Tibetan Buddhist painting on cotton, silk appliqué, usually depicting a Buddhist deity, scene, ...
, and
mandala A mandala ( sa, मण्डल, maṇḍala, circle, ) is a geometric configuration of symbols. In various spiritual traditions, mandalas may be employed for focusing attention of practitioners and adepts, as a spiritual guidance tool, for e ...
traditions, where holding the fully realized form in the mind is a prerequisite prior to creating an 'authentic' new art work that will provide a sacred support or foundation for deity.


Substitution effects

Mental imagery can act as a substitute for the imagined experience: Imagining an experience can evoke similar cognitive, physiological, and/or behavioral consequences as having the corresponding experience in reality. At least four classes of such effects have been documented. # Imagined experiences are attributed evidentiary value like physical evidence. # Mental practice can instantiate the same performance benefits as physical practice and reduction central neuropathic pain. # Imagined consumption of a food can reduce its actual consumption. # Imagined goal achievement can reduce motivation for actual goal achievement.


See also

*
Aphantasia Aphantasia ( , ) is the inability to create mental imagery. The phenomenon was first described by Francis Galton in 1880 but has since remained relatively unstudied. Interest in the phenomenon renewed after the publication of a study in 2015 ...
(condition whereby people can't think with mental images at all) *
Animal cognition Animal cognition encompasses the mental capacities of non-human animals including insect cognition. The study of animal conditioning and learning used in this field was developed from comparative psychology. It has also been strongly influen ...
* Audiation (imaginary sound) * Cognition *
Creative visualization Creative visualization is the cognitive process of purposefully generating visual mental imagery, with eyes open or closed, simulating or recreating visual perception, in order to maintain, inspect, and transform those images, consequently modi ...
*
Fantasy (psychology) In psychology, fantasy is a broad range of mental experiences, mediated by the faculty of imagination in the human brain, and marked by an expression of certain desires through vivid mental imagery. Fantasies are associated with scenarios that ar ...
*
Fantasy prone personality Fantasy prone personality (FPP) is a disposition or personality trait in which a person experiences a lifelong, extensive, and deep involvement in fantasy. This disposition is an attempt, at least in part, to better describe "overactive imagination ...
* Guided imagery * Imagination *
Internal monologue Intrapersonal communication is the process by which an individual communicates within themselves, acting as both sender and receiver of messages, and encompasses the use of unspoken words to consciously engage in self-talk and inner speech. Intr ...
*
Mental event A mental event is any event that happens within the mind of a conscious individual. Examples include thoughts, feelings, decisions, dreams, and realizations. Some believe that mental events are not limited to human thought but can be associated ...
*
Mental rotation Mental rotation is the ability to rotate mental representations of two-dimensional and three-dimensional objects as it is related to the visual representation of such rotation within the human mind. There is a relationship between areas of the bra ...
* Mind * Motor imagery *
Spatial ability Spatial ability or visuo-spatial ability is the capacity to understand, reason, and remember the visual and spatial relations among objects or space. Visual-spatial abilities are used for everyday use from navigation, understanding or fixing equi ...
*
Tulpa Tulpa is a concept in Theosophy, mysticism, and the paranormal, of an object or being that is created through spiritual or mental powers. Modern practitioners, who call themselves "tulpamancers", use the term to refer to a type of willed imaginary ...
*
Visual space Visual space is the experience of space by an aware observer. It is the subjective counterpart of the space of physical objects. There is a long history in philosophy, and later psychology of writings describing visual space, and its relationship ...
*
Vividness of Visual Imagery Questionnaire The Vividness of Visual Imagery Questionnaire (VVIQ) was developed in 1973 by the British psychologist David Marks (Marks, 1973). The VVIQ consists of 16 items in four groups of 4 items in which the participant is invited to consider the mental im ...


References


Further reading

* Albert, J.-M. ‘’Mental Image and Representation. (French text by
Jean-Max Albert Jean-Max Albert (born 1942) is a French painter, sculptor, writer, and musician. He has published theory, books on artists, and a collection of poems, plays and novels inspired by quantum physics. He perpetuated experiments initiated by Paul Klee ...
and translation by H. Arnold) Paris: Mercier & Associés, 2018

* Amorim, Michel-Ange, Brice Isableu and Mohammed Jarraya (2006) Embodied Spatial Transformations: “Body Analogy” for the Mental Rotation. Journal of Experimental Psychology: General. * * * Bennett, M.R. & Hacker, P.M.S. (2003). ''Philosophical Foundations of Neuroscience.'' Oxford: Blackwell. * * * Brant, W. (2013). Mental Imagery and Creativity: Cognition, Observation and Realization. Akademikerverlag. pp. 227. Saarbrücken, Germany. * * * Kieran Egan (educationist), Egan, Kieran (1992). ''Imagination in Teaching and Learning''. Chicago: University of Chicago Press. * * Finke, R.A. (1989). ''Principles of Mental Imagery.'' Cambridge, MA: MIT Press. * Garnder, Howard. (1987)
The Mind's New Science: A History of the Cognitive Revolution
' New York: Basic Books. * * Kosslyn, Stephen M. (1983). ''Ghosts in the Mind's Machine: Creating and Using Images in the Brain.'' New York: Norton. * Kosslyn, Stephen (1994)
Image and Brain: The Resolution of the Imagery Debate
'' Cambridge, MA: MIT Press. * * * * * * McGabhann. R, Squires. B, 2003, 'Releasing The Beast Within – A path to Mental Toughness', Granite Publishing, Australia. * McKellar, Peter (1957). ''Imagination and Thinking.'' London: Cohen & West. * * Paivio, Allan (1986). ''Mental Representations: A Dual Coding Approach.'' New York: Oxford University Press. * * * Pascual-Leone, Alvaro, Nguyet Dang, Leonardo G. Cohen, Joaquim P. Brasil-Neto, Angel Cammarota, and Mark Hallett (1995). Modulation of Muscle Responses Evoked by Transcranial Magnetic Stimulation During the Acquisition of New Fine Motor Skills. ''Journal of Neuroscience'

* * * Prinz, J.J. (2002).
Furnishing the Mind: Concepts and their Perceptual Basis
'' Boston, MA: MIT Press. * * Reisberg, Daniel (Ed.) (1992). ''Auditory Imagery.'' Hillsdale, NJ: Erlbaum. * Richardson, A. (1969). ''Mental Imagery.'' London: Routledge & Kegan Paul. * * Rohrer, T. (2006).
The Body in Space: Dimensions of embodiment
The Body in Space: Embodiment, Experientialism and Linguistic Conceptualization. In ''Body, Language and Mind, vol. 2.'' Zlatev, Jordan; Ziemke, Tom; Frank, Roz; Dirven, René (eds.). Berlin: Mouton de Gruyter. * Ryle, G. (1949). ''The Concept of Mind.'' London: Hutchinson. *Sartre, J.-P. (1940). ''The Psychology of Imagination.'' (Translated from the French by B. Frechtman, New York: Philosophical Library, 1948.) * * Skinner, B.F. (1974). ''About Behaviorism.'' New York: Knopf. * * * Thomas, N.J.T. (2003)

In L. Nadel (Ed.), ''Encyclopedia of Cognitive Science'' (Volume 2, pp. 1147–1153). London: Nature Publishing/Macmillan.


External links


Mental Imagery
in th
''Stanford Encyclopedia of Philosophy''
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