CHAPTER 6 (SUMMARY): PERCEPTION
Perception involves the selection, organization, and interpretation of sensory information. It
quickly became one of psychology’s primary concerns as early researchers attempted to explain
In organizing sensory data into whole perceptions, our first task is to discriminate figure from
ground. We then organize the figure into meaningful form by following certain rules for grouping
stimuli. We transform two-dimensional retinal images into three-dimensional perceptions by
using binocular cues, such as retinal disparity, and monocular cues, such as the relative sizes of
objects. Our brain computes motion as objects move across the retina. A quick succession of
images can also create an illusion of movement.
The perceptual constancies enable us to perceive objects as enduring in shape, size, and
lightness, regardless of viewing angle, distance, and illumination. The constancies explain
several well-known illusions.
Studies of sensory deprivation reveal that, for many species, infancy is a critical period
during which experience must activate the brain’s innate visual mechanisms. For example, when
cataracts are removed from adults who have been blind from birth, they can distinguish figure
and ground and they can perceive color, but they are unable to distinguish shapes and forms.
At the same time, human vision is remarkably adaptable. Given glasses that turn the world
upside down, people manage to adapt and move about with ease. Clear evidence that
perception is influenced by our experience comes from the many demonstrations of perceptual
set and context effects. Because perceptions vary, they may not be what the designer of a
machine assumes. Human factors psychologists study how people perceive and use machines
and how machines and physical environments can be better suited to that use.
Although parapsychologists have tried to document ESP, most research psychologists
remain skeptical, particularly because the results of experiments have not been reproducible.
How the process of perception is directed and limited by selective attention.
Selective attention means that at any moment, awareness focuses on only a limited aspect of all
that we are capable of experiencing. For example, even if a stimulus figure can evoke more than
one perception, we consciously experience only one at a time. The cocktail party effect provides
another example of selective attention. The ability to attend to one voice among many enables
us to converse coherently in the midst of auditory chaos. Selective attention also limits our
perception, as many stimuli will pass by unnoticed. This lack of awareness is evident in studies
of change blindness.