Sensation and perception

Sensation

The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Sensory receptors

Sensory nerve endings that respond to stimuli.

Perception

The process by which our brain organizes and interprets sensory information, enabling us to recognize objects and events as meaningful.

Bottom-Up Processing

Information processing that begins with the sensory receptors and works up to the brain’s integration of sensory information.

Top-Down Processing

Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

Transduction

Conversion of one form of energy into another; in sensation, the transforming of physical energy into neural impulses the brain can interpret.

Psychophysics

The study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.

Absolute Threshold

The minimum stimulus energy needed to detect a particular stimulus 50 percent of the time.

Signal Detection Theory

A theory predicting how and when we detect the presence of a faint stimulus amid background stimulation; assumes there is no single absolute threshold.

Subliminal

Below one's absolute threshold for conscious awareness.

Priming

The activation, often unconsciously, of certain associations that predispose one's perception, memory, or response.

Difference Threshold

The minimum difference between two stimuli required for detection 50 percent of the time; experienced as a just noticeable difference (jnd).

Weber’s Law

The principle that to be perceived as different, two stimuli must differ by a constant minimum percentage.

Sensory Adaptation

Diminished sensitivity as a consequence of constant stimulation.

Wavelength

The distance from the peak of one light wave or sound wave to the peak of the next.

Hue

The dimension of color determined by the wavelength of light; what we know as the color names blue, green, and so forth.

Intensity

The amount of energy in a light or sound wave, which influences perceived brightness or loudness; determined by the wave’s amplitude.

Cornea

The eye's clear, protective outer layer covering the pupil and iris.

Pupil

The adjustable opening in the center of the eye through which light enters.

Iris

A ring of muscle tissue that forms the colored portion of the eye and controls the size of the pupil opening.

Lens

The transparent structure behind the pupil that changes shape to help focus images on the retina.

Retina

The light-sensitive inner surface of the eye, containing receptor rods and cones and layers of neurons for processing visual information.

Accommodation

The process by which the eye’s lens changes shape to focus images of near or far objects on the retina.

Rods

Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision.

Cones

Retinal receptors concentrated near the center of the retina that function in daylight and detect fine detail and color.

Optic Nerve

The nerve that carries neural impulses from the eye to the brain.

Blind Spot

The point at which the optic nerve leaves the eye, creating a 'blind' spot because no receptor cells are located there.

Fovea

The central focal point in the retina, around which the eye's cones cluster.

Young-Helmholtz Trichromatic Theory

The theory that the retina contains three types of color receptors sensitive to red, green, and blue.

Opponent-Process Theory

The theory that opposing retinal processes enable color vision; explains after-images.

Feature Detectors

Nerve cells in the brain’s visual cortex that respond to specific features of the stimulus, such as shape or movement.

Parallel Processing

Processing multiple aspects of a problem simultaneously.

Audition

The sense or act of hearing.

Frequency

The number of complete wavelengths that pass a point in a given time.

Pitch

A tone's experienced highness or lowness; depends on frequency.

Middle Ear

The chamber between the eardrum and the cochlea containing tiny bones that concentrate vibrations.

Cochlea

A coiled, fluid-filled tube in the inner ear; converts sound pressure into electrical impulses.

Inner Ear

The innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.

Sensorineural hearing loss

Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve.

Conduction Hearing Loss

Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

Cochlear Implant

A device for converting sounds into electrical signals and stimulating the auditory nerve.

Place Theory

The theory linking pitch we hear to the place where the cochlea’s membrane is stimulated.

Frequency Theory

The theory that the rate of nerve impulses matches the frequency of a tone, enabling pitch sensing.

Gate-Control Theory

The theory that the spinal cord contains a neurological 'gate' that blocks or allows pain signals to pass.

Gustation

Our sense of taste.

Olfaction

Our sense of smell.

Kinesthesis

Our movement sense; our system for sensing the position and movement of body parts.

Vestibular Sense

Our balance sense; our sense of body movement and position.

Sensory Interaction

The principle that one sense may influence another.

Embodied Cognition

The influence of bodily sensations and gestures on cognitive preferences and judgments.