Chapter 04 - Sensation and Perception

absolute threshold

The minimum amount of physical energy (stimulation) needed for an observer to notice a stimulus

accommodation

In vision, the changes in the shape of the lens that focus light rays

amplitude

The difference between the minimum and maximum pressure levels in a sound wave, measured in decibels; this corresponds to the psychological property of loudness.

audition

Hearing.

auditory nerve

The bundle of sensory neurons that transmit auditory information from the ear to the brain.

binocular cells

Neurons that receive information from both eyes.

binocular cues

Visual input integrated from two eyes that provides perception of depth.

bipolar cells

Neurons in the retina that combine information from many receptors and excite ganglion cells.

blindsight

A phenomenon in which individuals with cortical lesions have no conscious visual awareness but can make discriminations about objects placed in front of them.

blind spot

The point on the retina where the optic nerve leaves the eye and which contains no receptor cells.

bottom-up processing

Perceptual processing that starts with raw sensory data that feed 'up' to the brain; what is perceived is determined largely by the features of the stimuli reaching the sense organs.

closure

A Gestalt rule of perception which states that people tend to perceive incomplete figures as complete.

cochlea

The three-chambered tube in the inner ear in which sound is transduced.

colour constancy

The tendency to perceive the colour of objects as stable despite changing illumination.

complexity

The extent to which a sound wave is composed of multiple frequencies.

cones

One of two types of photoreceptors, which are specialised for colour vision and allow perception of fine detail.

cornea

The tough, transparent tissue covering the front of the eyeball.

cycle

A single round of expansion and contraction of the distance between molecules of air in a sound wave.

decibel (dB)

The unit of measure of amplitude (loudness) of a sound wave.

depth perception

The organisation of perception in three dimensions; also called distance perception.

difference threshold

The smallest difference in intensity between two stimuli that a person can detect.

direct perception

A theory which states that sensory information intrinsically carries meaning.

eardrum

The thin, flexible membrane that marks the outer boundary of the middle ear; it is set in motion by sound waves and in turn sets in motion the ossicles; also called the tympanic membrane.

feature detector

A neuron that fires only when stimulation in its receptive field matches a particular pattern or orientation.

Fechner's law

The law of psychophysics r, that the subjective magnitude of a sensation grows as a proportion of the logarithm of the stimulus.

figure-ground perception

A fundamental rule of perception described by Gestalt psychology that states that people inherently differentiate between figure (the object they are viewing, sound to which they are listening, etc.) and ground (background).

form perception

The organisation of sensations into meaningful shapes and patterns.

fovea

The central region of the retina, where light is most directly focused by the lens.

frequency

In a sound wave, the number of cycles per second, expressed in hertz and responsible for subjective experience of pitch.

frequency theory

The theory of pitch that asserts that perceived pitch reflects the rate of vibration of the basilar membrane.

ganglion cells

Nerve cells in the retina that integrate information from multiple bipolar cells, the axons of which bundle together to form the optic nerve.

gate-control theory

Theory that emphasises the role of the central nervous system in regulating pain.

good continuation

A Gestalt rule of perception which states that, if possible, the brain organises stimuli into continuous lines or patterns rather than discontinuous elements.

gustation

Taste.

hair cells

Receptors for sound attached to the basilar membrane.

hertz (Hz)

The unit of measurement of frequency of sound waves.

hue

The sensory quality people normally consider colour.

iris

The ring of pigmented tissue that gives the eye its blue, green, or brown colour; its muscle fibers cause the pupil to constrict or dilate.

just noticeable difference (jnd)

The smallest difference in intensity between two stimuli that a person can detect

kinesthesia

The sense that provides information about the movement and position of the limbs and other parts of the body; receptors in joints transduce information about the position of the bones, and receptors in the tendons and muscles transmit messages about muscular tension.

lens

The disk-shaped, elastic structure of the eye that focuses light.

loudness

The psychological property corresponding to a sound wave's amplitude.

monocular cues

Visual input from a single eye alone that contributes to depth perception.

motion detectors

Ganglion cells that are particularly sensitive to movement.

motion parallax

A monocular depth cue involving the relative movements of retinal images of objects; nearby objects appear to speed across the field of vision, whereas distant objects barely seem to move.

motion perception

The perception of movement in objects.

Müler-Lyer illusion

A perceptual illusion in which two lines of equal length appear different in size

olfaction

Smell.

olfactory epithelium

Thin pair of structures in which transduction of smell occurs.

olfactory nerve

The bundle of axons from sensory receptor cells that transmits information from the nose to the brain.

opponent-process theory

A theory of colour vision that proposes the existence of three antagonistic colour systems: a blue-yellow system, a red-green system and a black-white system; according to this theory, the blue-yellow and red-green systems are responsible for hue, while the black-white system contributes to perception of brightness and saturation.

optic nerve

The bundle of axons of ganglion cells that carries information from the retina to the brain.

perception

The process by which the brain selects, organises and interprets sensations

percepts

Meaningful perceptual units, such as images of particular objects.

perceptual constancy

The organisation of changing sensations into percepts that are relatively stable in size, shape and colour.

perceptual illusions

Perceptual misinterpretations produced in the course of normal perceptual processes.

perceptual interpretation

The process of generating meaning from sensory experience.

perceptual organisation

The process of integrating sensations into meaningful perceptual units.

phantom limbs

Misleading 'sensations' from missing limbs.

pheromone

A chemical secreted by organisms in some species that allows communication between organisms.

pitch

The psychological property corresponding to the frequency of a sound wave; the quality of a tone from low to high.

place theory

A theory of pitch which proposes that different areas of the basilar membrane are maximally sensitive to different frequencies.

proprioceptive senses

Senses that provide information about body position and movement; the two senses are kinesthesia and vestibular sense.

proximity

A Gestalt rule of perception which states that, other things being equal, the brain groups objects together that are close to each other .

psychophysics

Branch of psychology that studies the relationship between attributes of the physical world and the psychological experience of them.

pupil

The opening in the centre of the iris that constricts or dilates to regulate the amount of light entering the eye.

receptive field

A region within which a neuron responds to appropriate stimulation.

recognition-by-components

The theory that asserts that we perceive and categorise objects in our environment by breaking them down into component parts and then matching the components and the way they are arranged against similar 'sketches' stored in memory.

response bias

In signal detection theory, the subject's readiness to report detecting a signal when uncertain; also called decision criterion.

retina

The light-sensitive layer of tissue at the back of the eye that transduces light into neural impulses.

rods

One of two types of photoreceptors; allow vision in dim light.

schema

Integrated pattern of knowledge stored in memory that organises information and guides the acquisition of new information.

sensation

The process by which the sense organs gather information about the environment.

sensory adaptation

The tendency of sensory systems to respond less to stimuli that continue without change.

sensory receptors

Specialised cells in the nervous system that transform energy in the environment into neural impulses that can be interpreted by the brain.

shape constancy

The perception that an object's shape remains constant despite the changing shape of the retinal image as the object is viewed from varying perspectives.

signal detection theory

The theory that experiencing a sensation means making a judgement about whether a stimulus is present or absent.

similarity

A Gestalt rule of perception which states that the brain tends to group similar elements within a perceptual field.

simplicity

A Gestalt rule of perception which states that people tend to perceive the simplest pattern possible.

size constancy

The perception that the shape of objects remains unchanged in spite of the fact that different impressions are made on the retina each time the object is encountered.

sound localisation

Identifying the location of a sound in space.

sound wave

A pulsation of acoustic energy

Stevens's power law

A law of sensation , which states that the subjective intensity of a stimulus grows as a proportion of the actual intensity raised to some power.

tastebuds

Structures that line the walls of the papillae of the tongue (and elsewhere in the mouth) that contain taste receptors.

timbre

The psychological property corresponding to a sound wave's complexity; the texture of a sound.

top-down processing

Perceptual processing that starts with the observer's expectations and knowledge.

transduction

The process of converting physical energy into neural impulses.

vestibular sense

The sense that provides information about the position of the body in space by sensing gravity and movement.

visual cliff

A clear table with a checkerboard directly beneath it on one side and another checkerboard that appears to drop off like a cliff on the other, used especially with human infants in depth perception studies.

wavelength

The distance over which a wave of energy completes a full oscillation.

Weber's law

The perceptual law that states that for two stimuli to be perceived as differing in intensity, the second must differ from the first by a constant proportion

'what' pathway

running from the striate cortex in the occipital lobes through the lower part of the temporal lobes, involved in determining what an object is.

'where' pathway

running from the striate cortex through the middle and upper regions of the temporal lobes and up into the parietal lobes, involved in locating an object in space, following its movement and guiding movement towards it.

Young-Helmholtz theory

A theory of colour vision which proposes that the eye contains three types of receptors, each sensitive to wavelengths of light that produce sensations of blue, green and red; by this theory, the colours that humans see reflect blends of the three colours to which the retina is sensitive; also called trichromatic theory.

trichromatic theory of colour

A theory that proposes that the eye contains three types of receptors, each sensitive to wavelengths of light that produce sensations of blue, green and red; by this theory, the colours that humans see reflect blends of the three colours to which the retina is sensitive; also called the Young-Helmholtz theory.