Chapter 5 - Sensation and Perception

Sensation

Sensation

the process by which stimuli are detected, transduced into nerve impulses, and sent to the brain

Perception

the process of organizing stimulus input and giving it meaning

Transduction

the conversion of one form of energy into another; in sensation, the process whereby physical stimuli are translated into nerve impulses

Psychophysics

the study of relations between the physical characteristics of stimuli and the sensory experiences they evoke

Absolute threshold

the lowest intensity at which a stimulus can be detected correctly 50 percent of the time

Subliminal Stimulis

a stimulus that is received by the senses but not perceived consciously

Decision Criterion

in signal detection theory, the potentially changing standard of how certain a person must be that a stimulus is present in order to report its presence

Signal Detection Theory

a theory that assumes that stimulus detection is not based on a fixed absolute threshold but rather is affected by rewards, punishments, expectations, and motivational factors

Difference Threshold

the smallest difference between two stimuli

Webers Law

the principle that to perceive a difference between two stimuli, the stimuli must differ by a constant percentage or ratio

Sensory Adaptation

diminishing sensitivity to an unchanging stimulus with the passage of time as sensory neurons habituate to the stimulation

Lens

the transparent structure behind the pupil that changes its shape to focus images on the retina

Retina

the light-sensitive back surface of the eye that contains the visual receptors

Myopia

a visual defect, sometimes called nearsightedness, in which the lens focuses distant images in front of the retina rather than on it

Hyperopia

a visual deficit sometimes called farsightedness in which the lens focuses the image behind the retina, reducing acuity for nearby objects

Rods

visual receptors that function under low levels of illumination and do not give rise to colour sensations

Cones

photoreceptors in the retina that function best in bright light and are differentially sensitive to red, green, or blue wavelengths; the retina's colour receptors

Fovea

a small area in the centre of the retina that contains only cones and in which visual acuity is greatest

Bipolar Cells

the second layer of retinal cells with which the rods and cones synapse

Ganglion Cells

the third layer of retinal cells with which the bipolar cells synapse and whose axons form the optic nerve

Optic Nerve

a bundle of ganglion cell axons in the retina that transmits visual information to the brain

Visual Acuity

the ability to see fine detail

Photopigments

protein molecules within the rods and cones whose chemical reactions when absorbing light result in nerve impulses being generated

Dark Adaptation

the progressive increase in brightness sensitivity that occurs over time as photopigments regenerate themselves during exposure to low levels of illumination

Trichromatic Theory

the colour vision theory originally advanced by Young and Helmholtz that there are three types of colour receptors in the retina and that combinations of activation of these receptors can produce perception of any hue in the visible spectrum

Opponent -Process Theory

the theory proposed by Hering that the retina contains three sets of colour receptors that respond differentially to red-green, blue-yellow, and black-white; the opponent processes that result can produce a perception of any hue

Dual-Process Theory

the modern colour vision theory that posits cones that are sensitive to red, blue, and green, and opponent processes at the level of ganglion cells and beyond

Primary Visual Cortex

the area of the occipital lobe which receives impulses generated from the retina via the thalamus and analyzes visual input by using its feature detectors

Feature detectors

sensory neurons that respond to particular features of a stimulus, such as its shape, angle, or colour

Parallel Processing

our ability to use our senses to take in a variety of information about an object and construct a unified image of its properties

Visual Association Cortex

cortical areas in the occipital, parietal, and temporal lobes that analyze visual stimuli sent to the primary visual cortex in relation to stored knowledge and that establish the "meaning" of the stimuli

Frequency

in audition, the number of cycles per second in a sound wave, responsible for the pitch of the sound; the measure of frequency is the hertz (Hz), which equals one cycle per second

Hertz (Hz)

the measure of sound wave frequency as cycles per second

Amplitude

the vertical size of the sound wave, which gives rise to the perception of loudness and is measured in terms of decibels

Decibel (db)

a logarithmic measure of sound intensity

Cochlea

a small coil-shaped structure of the inner ear that contains the receptors for sound

Basilar Membrane

a membrane that runs the length of the cochlea and contains the organ of Corti and its sound receptor hair cells

Oragn of corti

structure embedded in the basilar membrane that contains the hair cell receptors for sound

Frequency Theory

the theory of pitch perception that holds that the number of nerve impulses sent to the brain by the hair cells of the cochlea corresponds to the frequency of the sound wave; this theory is accurate at low frequencies

Place Theory

the theory of pitch perception that holds that sound frequencies are coded in terms of the portion of the basilar membrane where the fluid wave in the cochlea peaks; this theory accounts for perception of frequencies above 4000 Hz

Conduction Deafness

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

Nerve Deafness

hearing loss caused by damage to the cochlear receptor cells or the auditory nerve

Gustation

sense of taste

Olfaction

sense of smell

Taste Buds

the receptors for taste in the tongue and in the roof and back of the mouth that are sensitive to the qualities of sweet, sour, salty, and bitter

Olfactory bulb

a forebrain structure immediately above the nasal cavity odorus chemical excites only a limited portion of the olfactory bulb and coded in terms of where on that bulb the sense excites

Pheromones

chemical signals found in natural body scents

menstral synchrony

the tendency for some women who live together over time to become more similar to one another in the timing of their menstrual cycles

Gate Control theory

theory that proposes that the experience of pain results from the opening and closing of "gating mechanisms" in the nervous system

Endorphins

natural opiate-like substances that are involved in pain reduction

Kinesthesis

the body sense that provides feedback on the position and movements of our body parts

Vestibular Sense

the sense of body orientation or equilibrium

sensory prosthetic devices

devices that provide sensory input that can, to some extent, substitute for what blind and deaf people are not supplied by their sensory receptors

bottom-up processing

perceptual processing that begins with the analysis of individual elements of the stimulus and works up to the brain's integration of them into a unified perception

Top-down Processing

perceptual processing in which existing knowledge, concepts, ideas, or expectations are applied to make sense of incoming stimulation

Shadowing

an experimental procedure used in attention research in which a person simultaneously receives two or more messages, is asked to focus on one of them, and then is asked to report on the other messages as well

figure-ground relations

perceptual organization in which a focal stimulus is perceived as a figure against a background of other stimuli

Gestault Laws

the laws of perceptual organization advanced by the Gestalt psychologists similarity Proximity Closure Continuity

Perceptual Schemas

internal representations that contain the essential features of an object of perception

Perceptual Consistencies

recognize stimulus characteristics under varying conditions

Monocular Cues

depth cues that require only one eye; include linear perspective, decreasing size, height in the horizontal plane, texture, clarity, light and shadow, motion parallax, and interposition

Binocular Cues

depth cues that require the use of both eyes

Binocular Disparity

each eye sees a slightly different image

Convergence

a binocular depth cue produced by the muscles that rotate the eyes as they focus on nearby objects

Stroboscopic Movement

illusory movement produced when a light is briefly flashed in darkness and then, a few milliseconds later, another light is flashed nearby

Illusions

incorrect perceptions based on false perceptual hypotheses that often result from constancies that do not apply to the stimuli in question

Critical Period

a time period in which exposure to particular kinds of stimulation (e.g., perceptual) is required for normal development to occur

Deprivation Experiment

method of determining the critical periods during which certain experiences must occur for the related brain mechanisms to develop normally -cat stuck in containment with bars

Perceptual set

A readiness to perceive stimuli in a particular way

Inattention Blindness

the failure of unattended stimuli to register in consciousness

Tactile Sensations

Pressure (touch) Pain Warmth Cold

Synaesthesia

A condition in which stimuli are experienced not only in the normal sensory modality but in others as well

Subliminal Stimulus

A stimulus that is received by the senses but not perceived consciously

Trichromats

Normal colour vision They are sensitive to red-green, yellow-blue and black-white

Dichromat

Deficiency is caused by an absence of hue-sensitive photopigment in certain cone types. A person who is colour blind is in only of of the systems

Monocrhomat

Sensitive to only black-white system and is totally colour blind

Parallel Processing

Unified images created Modules which process colour, movement, shape, distance simultaneously

Photopigments

Protein molecules within the rods and cones whose chemical light result in nerve impulses being generated

Auditory cortex

totonic map, increasingly complex feature detectors, auditory association cortex

Adaptive significance

primary window into the chemical composition of what we ingest Seek out tastes that have caloric and nutritious value Avoid tastes that may have toxins

Inattentional Blindness

Failure of unattended stimuli to register in consciousness Gorilla and ball experiment

Perceptual set

readiness to perceive stimuli in a particular way top-down processing

Cognitive Penetrability

the extent to which knowing the trick diminishes the illusion