| Sensation | the activation of sensory receptors in various sense organs |
| just noticeable difference | the smallest difference between two stimuli that is detectable 50 percent of the time |
| absolute threshold | the smallest amount of energy needed for a person to consciously detect a stimulus 50 percent of the time it is present |
| rods and cones | specialized sensory receptors found in the eyes |
| habituation | the tendency of the brain to stop attending to constant, unchanging information |
| sensory adaptation | tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging |
| saccades | constant, movements of the eyes--little vibrations |
| subliminal stimuli | stimuli below the level of consciousness that may act upon behavior |
| perception | the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion |
| size constancy | the tendency to interpret an object as always being the same actual size, regardless of its distance |
| sensory receptors | specialized forms of neurons that are activated by different stimuli such as light and sound |
| shape constancy | the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina |
| brightness constancy | the tendency to perceive the apparent brightness of an object as the same even when the light conditions change |
| figure-ground | the tendency to perceive objects, or figures, as existing on a background |
| similarity | the tendency to perceive things that look similar to each other as being part of the same group |
| proximity | the tendency to perceive objects that are spacially close to each other as part of the same grouping |
| closure | the tendency to complete figures that are incomplete |
| continuity | the tendency to perceive things as simply as possible with continuous pattern rather than with a complex, broken-up pattern |
| contiguity | the tendency to perceive two things that happen close together in time as being related |
| depth perception | the ability to perceive the world in three dimensions |
| monocular cues | cues for perceiving depth based on one eye only |
| binocular cues | cues for perceiving depth based on both eyes |
| linear perspective | the tendency for parallel lines to appear to converge on each other |
| relative size | perception that occurs when objects that a person expects to be of a certain size appear to be small and are, therefore, assumed to be much further away |
| interposition | the assumption that an object that appears to be blocking part of another object is in front of the second object and closer to the viewer |