Your “mind’s eye” is your visual memory or imagination. Common examples of mental images include daydreaming, the mental visualization that occurs while reading a book, and the pictures summoned by athletes during training or before a competition.
This ability to create mental representations of things, people, and places that are absent from your visual field is important for problem-solving, memory, and spatial reasoning. Useful for humans, but it’s unlikely that animals can experience mental images.
The idea of having an “eye in our mind” first appeared in English in Chaucer’s (c. 1387) Man of Law’s Tale. However, the idea itself goes back at least to Cicero.
The term probably became known through the work of Shakespeare. He uses it in the best-known of all plays — Hamlet (1602), in a scene where Hamlet is recalling his father.
About 2% of people, when the eyes are closed, see only darkness, and such lack of ability is called aphantasia, though the other 98% can see colorful images. Hallucinogenic drugs increase that ability. Aphantasia does not seem to prevent creativity. Many aphantasics are successful in creative professions.
Aphantasics, being unable to visually summon the appearances of people they know and places they’ve been, can forget what their loved ones look like. They take photographs so that their memories are preserved. Meditation feels pointless, because the lack of mental imagery already gives them a clear mind.
Visual (as well as auditory, olfactory, etc.) imagery has long been researched in philosophy, psychology, cognitive science, and neuroscience. Mental imagery can sometimes produce the same effects as would be produced by the behavior or experience imagined.
The biological foundation of the mind’s eye is not fully understood, but the rudiments of are found in the deeper portions of the brain, where the center of perception exists. The pineal gland is a hypothetical candidate for producing a mind’s eye. Rick Strassman and others have postulated that during 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 evidence and plausible mechanism for DMT production.
According to psychologist and cognitive scientist Steven Pinker, we can use real images along with mental images to put together completely new images, thus seeing how the world works without having to directly experience it.
In The Mind’s Eye, Oliver Sacks tells the stories of people who are able to navigate the world and communicate with others despite losing the power of speech, the capacity to recognize faces, the sense of three-dimensional space, the ability to read, and the sense of sight. For all of these people, the challenge is to adapt to a radically new way of being in the world.
Sometimes when I’m driving, my physical eyes are watching the road, but my mind’s eye is visualizing a different scene. I try not to let myself do that; it’s scary as hell to “come to” and not remember how I got halfway across town.