1 Psychology and human development1.1 Sensation and perception
1.1 Visual and auditory perception
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Written by Resident Doctor Committee · Published
Sensation and perception
Sensation converts energy into neural activity. Perception interprets input that is often ambiguous, such as flat retinal images and overlapping sounds.
Bottom-up processing analyses stimulus features such as edges, frequencies and onsets.
Top-down processing uses experience, expectation, context, attention and motivation to interpret those features.
Perceptual set is a temporary readiness to perceive selectively, favouring one interpretation of a stimulus rather than allowing awareness of every aspect or reading.
Theories of perception
Theory | Claim | Struggles with |
|---|---|---|
Gregory, constructivist | The percept is built top-down from incomplete sensory data using stored knowledge | Speed of perception |
Gibson, direct or ecological | Information is picked up directly from the optic array, including affordances | Illusions and expectations |
Gestalt laws of organisation
Wertheimer, Koffka and Köhler held that perception is innately organised into wholes with properties absent from their parts. This sets Gestalt psychology apart from structuralism, constructivism and ecological theory.
The Gestalt laws are a named set describing how the visual system groups elements into unified wholes. Terms from depth perception, learning or attention, and familiarity, are not among them.
Law | Grouping rule |
|---|---|
Prägnanz (good form, simplicity) | The overarching law: perception settles on the simplest, most stable whole |
Proximity | Elements near one another group as one unit, even when nearness is the only link |
Similarity | Elements sharing colour, shape, size or brightness group, seen when spacing is equal in every direction |
Continuity (good continuation) | Elements along a smooth line or curve group as one continuous form, without filling gaps |
Closure | Gaps are filled so an incomplete figure is seen as a complete whole |
Common fate | Elements moving together in one direction group, which nearness alone cannot achieve |
Closure contributes to pareidolia.
Other visual organisation
Figure-ground segregation separates an object from its background, as in Rubin's vase, which alternates between a goblet and two profiles.
Constancy keeps perceived size or shape stable despite changes in distance or viewpoint.
Monocular depth cues include size, overlap, perspective, texture, shading and motion parallax, while convergence and retinal disparity support near depth.
Apparent motion
The phi phenomenon, first described by Wertheimer, is apparent movement when stationary stimuli are flashed in quick succession or alternation, so they are seen as one moving object.
The autokinetic effect is the apparent drift of a single small stationary light in an otherwise dark, featureless field.
Phi needs two or more stimuli in sequence, whereas autokinesis needs one light with no reference frame. Phi also differs from induced movement, the motion after-effect and illusions that distort size, shape or length, such as the Müller-Lyer lines.
Auditory perception
Pitch relates to frequency and loudness to amplitude, but neither relationship is direct.
Young adults hear from roughly 20 Hz to 20 kHz.
People localise sounds by timing differences below about 1.5 kHz and by intensity differences above it.
Phonemic restoration fills in speech masked by noise, using context.
Development of perception
Vision is the least developed sense at birth and matures mainly after birth, whereas touch, taste, smell and hearing already work, having matured before birth.
Newborn acuity is roughly 6/120, focus is best at 20 to 30 cm, and vision improves rapidly over the first year.
Early treatment of cataract, strabismus or unequal refraction protects vision, because delayed treatment risks persistent amblyopia.