The sense of smell.

The sense of taste.

The process that occurs when special neuron receptor sites in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain.

The process of converting outside stimuli, such as light, into neural activity.

The smallest difference between two stimuli that is detectable 50 percent of the time.

The lowest level of stimulation that a person can consciously detect 50 percent of the time the stimulation is present.

Tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging.

As a monocular cue of depth perception, the brain’s use of information about the changing thickness of the lens of the eye in response to looking at objects that are close or far away.

Visual sensory receptors found at the back of the retina, responsible for non-color sensitivity to low levels of light.

Visual sensory receptors found at the back of the retina responsible for color vision and sharpness of vision.

Theory of color vision that proposes three types of cones: red, blue, and green.

Theory of color vision that proposes visual neurons (or groups of neurons) are stimulated by light of one color and inhibited by light of another color.

The visible part of the ear.

Theory of pitch that states that different pitches are experienced by the stimulation of hair cells in different locations on the organ of Corti.

Theory of pitch that states the pitch is related to the speed of vibrations in the basilar membrane.