Griggs Psychology - Chapter 3

absolute threshold

the minimum amount of energy in a sensory stimulus detected 50 percent of the time

signal detection theory

a theory that assumes that the detection of faint sensory stimuli depends not only upon a person's physiological sensitivity to a stimulus but also upon his decision criterion for detection, which is based on non-sensory factors

difference threshold

the minimum difference between two sensory stimuli detected 50 percent of the time. The difference threshold is also sometimes referred to as the just noticeable difference, or jnd

Weber's law

for each type of sensory judgement that we can make, the measured difference threshold is a constant fraction of the standard stimulus value used to measure it. This constant fraction is different for each type of sensory judgement

Steven's power law

the perceived magnitude of a stimulus is equal to its actual physical intensity raised to some constant power. The constant power is different for each type of sensory judgement

sensory adaptation

our sensitivity to unchanging and repetitious stimuli disappears over time

wavelength

the distance in one cycle of a wave, from one crest to another

amplitude

the amount of energy in a wave, its intensity, which is the height of the wave at its crest

frequency

the number of times a wave cycles in one second

transduction

the conversion of physical energy into neural signals that the brain can understand

accommodation

the focusing of light waves from objects of different distances directly on the retina

nearsightedness

a visual problem in which the light waves from distant objects come into focus in front of the retina, blurring the images of these objects

farsightedness

a visual problem in which the light waves from nearby objects come into focus behind the retina, blurring the images of these objects

retina

the light-sensitive layer of the eye that is composed of three layers of cells--ganglion, bipolar, and receptor (rods and cones)

blindsight

a condition in which a blind person has some spared visual capacities in the absence of any visual awareness

rods

receptor cells in the retina that are principally responsible for dim light and achromatic vision

cones

receptor cells in the retina that are principally responsible for bright light and color vision

fovea

a tiny pit in the center of the retina filled with cones

dark adaptation

the process by which the rods and cones through internal chemical changes become more and more sensitive to light in dim light conditions

trichromatic theory

a theory of color vision that assumes that there are three types of cones, each only activated by wavelength ranges of light corresponding roughly to blue, green, and red. It further assumes that all of the various colors that we can see are mixtures of various levels of activation of the three types of cones. If all three are equally activated, we see white.

additive mixtures

direct mixtures of different wavelengths of light in which all of the wavelengths reach the retina and are added together

subtractive mixtures

mixtures of wavelengths of light in which some wavelengths are absorbed (subtracted) and so do not get reflected from the mixtures to the retina

complementary colors

wavelengths of light that when added together produce white

opponent-process theory

a theory of color vision that assumes that there are three opponent-process cell systems (red-green, blue-yellow, and black-white) that process color information after it has been processed by the cones. The colors in each system oppose one another in that if one color is stimulated, the other is inhibited.

hair cells

the receptor cells for hearing. they line the basilar membrane inside the cochlea

nerve deafness

hearing loss created by damage to the hair cells or the auditory nerve fibers in the inner ear

conduction deafness

hearing loss created by damage to one of the structures in the ear responsible for mechanically conducting the auditory information to the inner ear

place theory

a theory of pitch perception which assumes that there is a specific location along the basilar membrane that will maximally respond to a particular frequency, thereby indicating the pitch to the brain. As this location goes down the basilar membrane from the oval window, the pitch goes down from 20,000 Hz to 20 Hz

frequency theory

a theory of pitch perception that assumes that the frequency of the sound wave is mimicked by the firing rate of the entire basilar membrane

volley principle

cells taking turns firing will increase the maximum firing rate for a group of cells

sensation

the initial information gathering and recoding by the sensory structures

perception

the interpretation by the brain of sensory information

bottom-up processing

the processing of incoming sensory information as it travels up from the sensory structures to the brain

top-down processing

the brain's use of knowledge, beliefs, and expectations to interpret sensory information

perceptual set

the interpretation of ambiguous sensory information in terms of how our past experiences have set us to perceive it

contextual effect

the use of the present context of sensory information to determine its meaning

figure-and-ground principle

the Gestalt perceptual organizational principle that the brain organizes sensory information into a figure or figures (the center of attention) and ground (the less distinct background)

closure

the Gestalt perceptual organizational principle that the brain completes (closes) incomplete figures to form meaningful objects

subjective contour

A line or shape that is perceived to be present but does not really exist. The brain creates it during perception

perceptual constancy

the perceptual stability of the size, shape, brightness, and color for familiar objects seen at varying distances, different angles, and under different lighting conditions

depth perception

our ability to perceive the distance of objects from us

retinal disparity

a binocular depth cue referring to the fact that as the disparity (difference) between the two retinal images of an object increases, the distance of the object from us decreases

linear perspective

A monocular depth cue referring to the fact that as parallel lines recede away from us, they appear to converge--the greater the distance, the more they seem to converge. Sometimes referred to as perspective convergence.

interposition

A monocular depth cue referring to the fact that if one object partially blocks our view of another, we perceive it as closer to us

proprioception

sense of where your body & limbs are located in space

tactile sensation

sense of touch (really pressure) that isn't painful

nociception

pain sensations elicited by noxious stimuli (happens everywhere but the brain)

temperature

separate reactions from cells sensitive to stimuli that are either warmer or colder than the body