subliminal perception: see perception.

perception, in psychology, mental organization and interpretation of sensory information. The Gestalt psychologists studied extensively the ways in which people organize and select from the vast array of stimuli that are presented to them, concentrating particularly on visual stimuli. Perception is influenced by a variety of factors, including the intensity and physical dimensions of the stimulus; such activities of the sense organs as effects of preceding stimulation; the subject's past experience; attention factors such as readiness to respond to a stimulus; and motivation and emotional state of the subject. Stimulus elements in visual organization form perceived patterns according to their nearness to each other, their similarity, the tendency for the subject to perceive complete figures, and the ability of the subject to distinguish important figures from background. Perceptual constancy is the tendency of a subject to interpret one object in the same manner, regardless of such variations as distance, angle of sight, or brightness. Through selective attention, the subject focuses on a limited number of stimuli, and ignores those that are considered less important. Depth perception, considered to be innate in most animals, is produced by a variety of visual cues indicating perspective, and by a slight disparity in the images of an object on the two retinas. An absolute threshold is the minimal physical intensity of a stimulus that a subject can normally perceive, whereas a difference threshold is the minimal amount of change in a stimulus that can be consciously detected by the subject. Recent studies have shown that stimuli are actually perceived in the brain, while sensory organs merely gather the signals. William Dobelle's research, for instance, has offered significant hope for the blind.

extrasensory perception: see parapsychology.

Process of registering sensory stimuli as meaningful experience. The differences between sensation and perception have varied according to how the terms are defined. A common distinction is that sensations are simple sensory experiences, while percepts are complex constructions of simple elements joined through association. Another is that perception is more subject to the influence of learning. Though hearing, smell, touch, and taste perceptions have all been explored, vision has received the most attention. Structuralist researchers such as Edward Bradford Titchener focused on the constituent elements of visual perceptions, whereas Gestalt psychology has stressed the need to examine organized wholes, believing humans are disposed to identifying patterns. Visual objects tend to appear stable despite continually changing stimulus features (such as ambient light, perspective, ground vs. figure arrangement), which enables an observer to match a perceived object with the object as it is understood to exist. Perceptions may be influenced by expectations, needs, unconscious ideas, values, and conflicts.

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Perception that involves awareness of information about something (such as a person or event) not gained through the senses and not deducible from previous experience. Classic forms of ESP include telepathy, clairvoyance, and precognition. No conclusive demonstrations of the existence of ESP in any individual have been given, but popular belief in the phenomenon remains widespread, and people who claim to possess ESP are sometimes employed by investigative teams searching for missing persons or things. Seealso parapsychology.

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