Absolute refractory period
The minimum length of time after an action potential during which another action potential cannot begin.
The minimum amount of stimulation that an organism can detect for a specific type of sensory input.
An inherited characteristic that increased in a population (through natural selection) because it helped solve a problem of survival or reproduction during the time it emerged.
Additive color mixing
Formation of colors by superimposing lights, putting more light in the mixture than exists in any one light by itself.
A structure that runs the length of the cochlea in the inner ear and holds the auditory receptors, called hair cells.
People, objects, events, and other standards that are used as a baseline for comparisons in making judgments.
A cue to depth that involves sensing the eyes converging toward each other as they focus on closer objects.
Making a large request that is likely to be turned down as a way to increase the chances that people will agree to a smaller request later.
A device that monitors the electrical activity of the brain over time by means of recording electrodes attached to the surface of the scalp.
The entire family of internally produced chemicals that resemble opiates in structure and effects.
A vision deficiency in which distant objects are seen clearly but close objects appear blurry.
The process of detecting specific elements in visual input and assembling them into a more complex form.
Neurons that respond selectively to very specific features of more complex stimuli.
A psychophysical law stating that larger and larger increases in stimulus intensity are required to produce perceptible increments in the magnitude of sensation.
A tiny spot in the center of the retina that contains only cones; visual acuity is greatest at this spot.
The theory that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates.
The idea that incoming pain sensations must pass through a "gate" in the spinal cord that can be closed, thus blocking pain signals.
A theoretical orientation based on the idea that the whole is greater than the sum of its parts.
Objects that can be represented in two-dimensional pictures but cannot exist in three-dimensional space.
Just noticeable difference (JND)
The smallest difference in the amount of stimulation that a specific sense can detect.
The sensory system that monitors the positions of the various parts of one's body.
A process in the retina that occurs when neural activity in a cell opposes activity in surrounding cells.
Cue to depth that involves images of objects at different distances moving across the retina at different rates.
A vision deficiency in which close objects are seen clearly but distant objects appear blurry.
Opponent process theory
The theory that color perception depends on receptors that make antagonistic responses to three pairs of colors.
The point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain.
An apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality.
A tendency to experience a stable perception in the face of continually changing sensory input.
An inference about which distal stimuli could be responsible for the proximal stimuli sensed.
The idea that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane.
The fact that subjects' expectations can lead them to experience some change even though they receive an empty, fake, or ineffectual treatment.
The opening in the center of the iris that helps regulate the amount of light passing into the rear chamber of the eye.
Receptive field of a visual cell
The retinal area that, when stimulated, affects the firing of that cell.
The neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain.
A cue to the depth based on the fact that objects within 25 feet project images to slightly different locations on the left and right retinas, so the right and left eyes see slightly different views of the object.
A drawing that is compatible with two different interpretations that can shift back and forth.
A psychophysiological theory proposing that the detection of stimuli involves decision processes as well as sensory processes, which are influenced by a variety of factors besides the physical intensity of a stimulus.
Subtractive color mixing
Formation of colors by removing some wavelengths of light, leaving less light than was originally there.
The theory of color vision holding that the human eye has three types of receptors with differing sensitivities to different wavelengths.
The sensory system that responds to gravity and keeps people informed of their body's location in space.
The theory holding that groups of auditory nerve fibers fire neural impulses in rapid succession, creating volleys of impulses.