Glossary of Key Terms
Affordances: in Gibson’s theory, the possible uses of objects, which are claimed to be given directly in the
sensory information provided by the stimulus.
Amblyopia: an eye condition in which there is impaired vision in one eye that is not due to physiological
damage; commonly referred to as lazy eye.
Apperceptive agnosia: a form of visual agnosia in which there is impaired perceptual analysis of familiar
objects.
Associative agnosia: a form of visual agnosia in which perceptual processing is fairly normal, but there is
an impaired ability to derive the meaning of objects.
Bottom-up processing: gathering information directly from the external environment, as distinct from the
effects of expectations (top-down processing).
Double dissociation: the finding that some brain-damaged individuals do well on task A and poorly on
task B, whereas others show the opposite pattern.
Habituation method: a way of assessing perception in young children based on habituation (the gradual
reduction in the attention paid to a stimulus that is repeated several times).
Invariants: in Gibson’s theory those aspects of the visual environment that remain the same as the
observer moves.
Maturation: aspects of development in children owing little to learning or experience.
Optic array: in Gibson’s theory, the pattern of light reaching the eye.
Optic flow pattern: perceptual effect in which the visual environment appears to move away from the point
towards which a person is moving.
Prosopagnosia: a condition caused by brain damage in which the patient cannot recognise familiar faces,
but can recognise familiar objects.
Resonance: Gibson’s explanation for how we detect invariant sensory information; the information is there
in the environment and one simply tunes into it.
Shape constancy: objects are perceived to have a given shape regardless of the angle from which they are
viewed.
Size constancy: objects are perceived as having a given size regardless of the size of the retinal image.
Texture gradient: a cue to depth given by the increased rate of change in texture density as you look from
the front to the back of a slanting stimulus.
Top-down processing: processing that is affected by expectations and prior knowledge, as distinct from
bottom-up processing, which is driven directly by the stimulus.
Visual agnosia: a condition where individuals can see but fail to be able to recognise objects.