Chapter 3: Sensation and Perception

Sensation

The process of receiving stimulus energies from the external environment and transforming those energies into neural energy

Perception

The process of organizing and interpreting sensory information so that it makes sense

bottom-up processing

• The operation in sensation and perception in which sensory receptors register information about the external environment and send it up to the brain for interpretation.

• Begins with the external world

top-down processing

The operation in sensation and perception, launched by cognitive processing at the brain’s higher levels, that allows the organism to sense what is happening and to apply that framework to information from the world.

sensory receptors

Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain.

absolute threshold

The minimum amount of stimulus energy that a person can detect.

difference threshold

The degree of difference that must exist between two stimuli before the difference is detected.

signal detection theory

An approach to perception that focuses on decision making about stimuli in the presence of uncertainty.

selective attention

The act of focusing on a specific aspect of experience while ignoring others.

perceptual set

A predisposition or readiness to perceive something in a particular way

sensory adaptation

A change in the responsiveness of the sensory system based on the average level of surrounding stimulation.

Retina

The multilayered light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain.

Rods

The receptor cells in the retina that are sensitive to light but not very useful for color vision

Cones

The receptor cells in the retina that allow for color perception

visual cortex

Located in the occipital lobe, the part of the cerebral cortex involved in vision

feature detectors

Neurons in the brain’s visual system that respond to particular features of a stimulus. These detectors pick up the edges, shapes, colors, and contours of stimuli

Trichromatic theory

Theory stating that color perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths

Opponent-process theory

Theory stating that cells in the visual system respond to complementary pairs of red-green and blue-yellow colors; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue

figure ground relationship

The principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (ground)

gestalt psychology

A school of thought interested in how people naturally organize their perceptions according to certain patterns. Ex. The whole is different from the sum of its parts

depth perception

The ability to perceive objects three dimensionally

Binocular cues

Depth cues that depend on the combination of the images in the left and right eyes and on the way the two eyes work together.

Monocular cues

Powerful depth cues available from the image in one eye, either the right or the left.

Perceptual constancy

The recognition that objects are constant and unchanging even though sensory input about them is changing.

Size constancy

The recognition that an object remains the same size even though the retinal image of the object changes

Shape constancy

The recognition that an object retains the same shape even though its orientation to you changes.

Color constancy

The recognition that an object retains the same color even though different amounts of light fall on it.

cochlea

A tubular, fluid-filled structure that is coiled up like a snail

kinesthetic sense

Senses that provide information about movement, posture, and orientation

vestibular sense

Sense that provides information about balance and movement.

Christine Ladd-Franklin, Ph.D.

Her research interests were expanding from math and logic to the new field of psychology and specifically the visual sense. She published her first article in psychology in 1887 on binocular vision. She was especially interested in Helmholtz's theory of color vision. She was a trailblazer for women in higher education. She considered herself a mathematician, logician, psychologist, innovator, and feminist.