CHAPTER 4 DEFINITIONS PSYC 1F90

Transducers

Devices that convert one kind of energy into another.

Sensation

Conversion of energy from the environment into a pattern of response by the nervous system; also, a sensory impression.

Psychophysics

Study of how the mind interprets the physical properties of stimuli.

Absolute threshold

Minimum amount of physical energy that can be detected 50 percent of the time.

Difference threshold

Minimum difference in physical energy between two stimuli that can be detected 50 percent of the time.

Sensory adaptation

A decrease over time in sensory response to an unchanging stimulus.

Perceptual features

Basic attributes of a stimulus, such as lines, shapes, edges, or colors.

Feature detector

Cells in the cortex that respond to a specific attribute of an object.

Hue

Color of light, as determined by its wavelength.

Cornea

Curved, transparent, protective layer through which light enters the eye.

Lens

Clear structure behind the pupil that bends light toward the retina.

Accommodation

Changes in the shape of the lens of the eye to enable the seeing of close and far objects.

Hyperopia

Having difficulty focusing on nearby objects (farsightedness).

Myopia

Having difficulty on distant objects (nearsightedness).

Astigmatism

Defects in the cornea, lens, or eye that cause some areas of vision to be out of focus.

Presbyopia

Farsightedness caused by aging.

Retina

Surface at the back of the eye onto which the lens focuses light rays.

Cones

Photoreceptors that are sensitive to color.

Rods

Photoreceptors for dim light that produce only black and white sensations.

Visual acuity

The sharpness of visual perception.

Blind spot

Area in the retina where the optic nerve exits that contains no photoreceptor cells.

Optic nerve

Structure that conveys visual information away from the retina to the brain.

Fovea

Tiny spot in the center of the retina, containing only cones, where visual acuity is greatest.

Color blindness

A total inability to perceive color.

Color weakness

An inability to distinguish some colors.

Peripheral (side) vision

Vision at the edges of the visual field.

Dark adaptation

Increased light sensitivity of the eye under low-light conditions.

Pupil

The black opening inside the iris that allows light to enter the eye.

Iris

Colored structure on the surface of the eye surrounding the pupil.

Trichromatic theory of color vision

A theory of color vision based on three cone types: red, green, and blue.

Opponent-process theory of color vision

Proposition that color vision is based on coding things as red or green, yellow or blue, or black or white.

Pitch

How high or low a tone sounds; related to the frequency of a sound wave.

Loudness

The volume of a sound; related to the amplitude of a sound wave.

Eardrum

Membrane that vibrates in response to sound waves and transmits them inward.

Cochlea

Snail-shaped organ in the inner ear that contains sensory receptors for hearing.

Basilar membrane

Structure in the cochlea containing hair cells that convert sound waves into action potentials.

Hair cells

Receptor cells within the cochlea that transduce vibrations into nerve impulses.

Conductive hearing loss

Poor transfer of sounds from the eardrum to the inner ear.

Sensorineural hearing loss

Loss of hearing caused by damage to the inner-ear hair cells or auditory nerve.

Noise-induced hearing loss

Damage caused by exposing the hair cells to excessively loud sounds.

Frequency theory of hearing

Proposition that pitch is decoded from the rate at which hair cells of the basilar membrane are firing.

Place theory of hearing

Proposition that higher and lower tones excite specific areas of the cochlea.

Olfaction

Sense of smell.

Gustation

Sense of taste.

Skin senses

The senses of touch, pressure, pain, heat, and cold.

Kinesthetic senses

The senses of body movement and positioning.

Vestibular senses

Perception of balance, gravity, and acceleration.

Lock-and-key theory of olfaction

A theory holding that odors are related to the shapes of chemical molecules.

Taste buds

Receptor cells for taste.

Warning system

Pain based on large nerve fibers; warns that bodily damage may be occurring.

Reminding system

Pain based on small nerve fibers; reminds the brain that the body has been injured.

Gate control theory

A theory proposing that pain messages pass through neural "gates" in the spinal cord.

Multimodal integration

The process by which the brain combines information coming from multiple senses.

Selective attention

Giving priority to a particular incoming sensory message.

Inattentional blindness

A failure to notice a stimulus because attention is focused elsewhere.

Change blindness

A failure to notice that the background is changing because attention is focused elsewhere.

Mind-wandering

The process by which attention is withdrawn from the physical environment to focus on internal events.

Synesthesia

A perceptual phenomenon in which stimulation of one sensory system creates perceptual experiences in another sensory system.

Perception

Selection, organization, and interpretation of sensory input.

Illusion

A misleading or misconstructed perception.

Hallucination

Perception with no basis in reality.

Perceptual construction

A mental model of external events.

Bottom-up processing

Organizing perceptions by beginning with low-level features.

Top-down processing

Perception guided by prior knowledge or expectations.

Figure-ground organization

Organizing a perception so that part of a stimulus appears to stand out as an object (figure) against a less prominent background (ground).

Size constancy

The principle that the perceived size of an object remains constant, despite changes in its retinal image.

Brightness constancy

The principle that the apparent (or relative) brightness of objects remains the same so long as they are illuminated by the same amount of light.

Müller-Lyer illusion

Two equal-length lines tipped with inward or outward pointing Vs appear to be of different lengths.

Depth perception

The ability to see three-dimensional (3-D) space and to judge distances accurately.

Depth cues

Features of the environment and messages from the body that supplies information about distance and space.

Binocular depth cues

Perceptual features that impart information about distance and three-dimensional (3-D) space that require two eyes.

Retinal disparity

Difference between the images projected onto each eye.

Stereoscopic vision

Perception of space and depth as a result of each eye receiving different images.

Convergence

Degree to which the eyes turn in to focus on a close object.

Monocular depth cues

Perceptual features that impart information about distance and three-dimensional (3-D) space that require just one eye.

Pictorial depth cues

Monocular depth cues found in paintings, drawings, and photographs that impart information about space, depth, and distance.

Virtual reality

Environment in which sensory stimuli (such as sights and sounds) are provided by computer software to realistically simulate 'real world' events.

Endocrine system

A network of glands that release hormones into the bloodstream.

Hormones

A chemical released by the endocrine glands.

Pituitary gland

The master gland of the endocrine system that controls the action of all other glands.

Growth hormone

A hormone, secreted by the pituitary gland, that promotes body growth.

Oxytocin

A hormone, released by the pituitary gland, that plays a broad role in regulating pregnancy, parenthood, sexual activity, social bonding, trust, and even reducing stress reactions.

Pineal gland

A gland in the brain that helps regulate body rhythms and sleep cycles.

Melatonin

A hormone released by the pineal gland in response to daily cycles of light and dark.

Thyroid gland

An endocrine gland that helps regulate the rate of metabolism.

Adrenal glands

Endocrine glands that arouse the body, regulate salt balance, adjust the body to stress, and affect sexual functioning.

Epinephrine

An adrenal hormone that tends to arouse the body; epinephrine is associated with fear. (Also known as adrenaline.)

Norepinephrine

Both a brain neurotransmitter and an adrenal hormone that tends to arouse the body; norepinephrine is associated with anger. (Also known as noradrenaline.)

Self-regulation

The ability to consciously exert self-control.