Chapter 4 Definitions

threshold

A point which a stimulus triggers a response

stimulus intensity

How intense a stimulus has to be in order for it to be in detected

Absolute threshold

The weakest detectable stimulus

different threshold

The lowest intensity of stimulation needed to create a noticable difference between stimuli

Signal detection theory

emphasises the psychological state that influences the detection of a stimulus

Lens

A transparent eye structure that focuses the light rays falling on the retina

nearsightedness

Vision problem in which close objects are seen clearly but distance objects appear blurry

farsightedness

Vision problem in which distant objects are seen clearly but close objects appear blurry.

pupil

that opening in the centre of the iris that helps regulate the amount of light passing into the rear chamber of the eye

Retina

The neural tissue lining the inside back surface of the eye; it absorbs light, processes images and sends visual information to the brain

Cones

specialised visual receptors that play a key role in daylight vision and colour vision

fovea

A tiny spot in the centre of the retina that contains only cones; visual acuity is great at the spot

rods

specialised visual receptors that play a key role in night vision and peripheral vision

dark adaptation

The process in which the eyes become more sensitive to light and low illumination

light adaptation

The process in which the eyes become less sensitive to light in high illumination

receptive field of a visual cell

The retinal area that, when stimulated, affects the firing of that cell

Optic chiasm

The point at which the axons from the inside half of the eye crossover and then project to the opposite of half of the brain

feature detectors

Neurons that respond selectively to very specific features of more complex stimuli

subtracted colour mixing

Works by removing some wavelength of light, leaving less light than was originally there.

additive colour mixing

works by super imposing lights, putting more lights in the mixture than exist in any one light by itself

trichromatic theory

Holds that the human eye has three types of receptors with differing sensitivity to different light wavelengths

colour blindness

encompasses a variety of deficiencies in the ability to distinguish among colours

complementary colours

Pairs of colours that produce grey tones when mixed together

after-image

A visual image that persists after a stimulus removed

the opponent process theory

holds that colour perception depends on receptors that make antagonistic responses to 3 pairs of colour

cochlea

A fluid-filled, coiled tunnel that contains the receptors for hearing

Basilar membrane

runs the length of the spiral-shaped cochlea, holds the auditory receptors, called hair cells

Place theory

suggests that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane

frequency theory

States that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates

Auditory localisation

Locating the source of a sound in space

The gustatory system

The sensory system for taste

The olfactory system

The sensory system will smell