Chapter 7 Sensation and Perception

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Chapter 7 Sensation and Perception

sensation

The study of the relationship between physical stimulation and its psychological effects.

perception

How we recognize, interpret, and organize our sensations.

detection

The act of sensing a stimulus

absolute threshold

The minimal amount of stimulation needed to detect a stimulus and cause the neuron to fire 50% of the time.

signal detection theory

This theory takes into consideration that there are four possible outcomes on each trial in a detection experiment: hit, miss, false alarm, and correct rejection.

hit

The signal was present, and the participant reported sensing it.

miss

The signal was present, but the participant did not sense it.

false alarm

The signal was absent, but the participant reported sensing it.

correct rejection

The signal was absent, and the participant did not report sensing it.

difference threshold (also just noticeable difference- JND)

The minimum amount of distance between two stimuli that can be detected as distinct.

Ernst Weber

He noticed that at low weights (like 1oz) it was easy to notice a 0.5oz increase or decrease in weight; but at higher weights (like 32oz) participants were not able to judge 0.5oz differences.

Weber's Law

This law states that the greater magnitude of the stimulus, the larger the differences must be noted.

subliminal perception

a form of preconscious processing that occurs when we are presented with stimuli so rapidly that we are not consciously aware of them.

receptor cells

specialized cells designed to detect specific types of energy.

receptive field

the area from which our receptor cells receive input.

transduction

The term describing the process which the form of the input is converted into the electrochemical form of communication used by the nervous system. Takes place at the level of the receptor cells.

contralateral shift

the switch of sensory input from one side of the body to the opposite side of the brain.

Olfaction

the sense of smell.

sensory coding

the process by which receptors convey such a range of information to the brain.

single cell recording

a technique by which the firing rate and pattern of a single receptor cell can be measured in response to varying sensory input.

visual sensation

when the eye receives light input from the outside world.

distal stimulus

the object as it exists in the environment.

proximal stimulus

the image of the object on the retina- it is later inverted and the brain interprets the image correctly.

cornea

a protective layer on the outside of the eye.

lens

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

retina

located at the back of the eye and covered with receptor cells (rods and cones)

rods

located on the periphery of the retina and are sensitive to low light.

cones

located in the center of the retina (or fovea) and are sensitive to bright light and color vision.

bipolar cells

specialized cells which connect rods and cones to the ganglion cells of the optic nerve.

amacrine cells

Between the ganglion cells and the bipolar cells.

optic nerves

nerves that carry visual information from the eyes to the brain.

optic chiasma

the crossing of the optic nerves from the two eyes at the base of the brain.

feature detector neurons

"see" different parts of the pattern such as a line set at a specific angle to background.

Young-Helmoltz or trichromatic theory

According to this theory, the cones in the retina of the eyes are activated by light waves associated with blue, red, and green. We see all colors by mixing these three colors.

opponent process theory

The theory contends that cells within the thalamus respond to opponent pairs of receptor sets- namely black/white, red/green, and blue/yellow. If one color of the set is activated, the other is essentially turned off.

afterimage

if you stare at a red dot on a page and turn away to a blank piece of white paper, you will see a green dot on the blank piece of paper- this is known as the ________.

dichromats

people who cannot distinguish between the red/green or blue/yellow continuums.

monochromats

people who see only in shades of black and white.

auditory input

the form of sound waves that enters the ear by passing the outer ear and into the ear canal.

tympanic membrane

the membrane in the ear that vibrates to sound; known as the eardrum.

ossicles

The three small bones found in the middle ear (the malleus, the incus, and the stapes) that help to amplify the vibrations from sound waves. The malleus is atached to the tympanic membrane and the stapes is attached to the oval window of the cochlea.

cochlea

the snail-shaped tube (in the inner ear coiled around the modiolus) where sound vibrations are converted into nerve impulses by the Organ of Corti.

vestibular sacs

Sacs in the inner ear that are responsible for sensing gravitation and forward, backward, and vertical movement.

place theory

theory that asserts that sound waves generate activity at different places along the basilar membrane.

frequency theory

theory that states that we sense pitch because the rate of neural impulses is equal to the frequency of a particular sound.

conductive deafness

damage to the outer or middle ear structure or the neural pathway.

sensorineural deafness

nerve deafness

gustation

taste

four basic tastes

sweet, salty, sour, bitter

cutaneous and tactile receptors

receptor cells located in the skin that provide information about pain, pressure, and temperature.

cold fibers

receptor cells that fire in response to cold stimuli

warm fibers

receptor cells that fire in response to warm stimuli

vestibular sense

involves sensation of balance.

kinesthesis

found in joints and ligaments, transmits information about the location and position of the limbs and body parts.

adaptation

an unconscious, temporary change in response to environmental stimuli.

habituation

the process by which we become accustomed to a stimulus and notice it less and less over time.

dihabituation

occurs when a change in the stimulus, even a small change, causes us to notice the stimulus again.

attention

the processing through cognition of a select portion of the massive amount of information incoming from the senses and contained in memory.

selective attention

when we try to attend to one thing while ignoring another.

cocktail part phenomenon

our ability to carry on and follow a single conversation in a room full of conversations.

filter theories

these theories propose that stimuli must pass through some sort of screen or filter to enter into attention.

attentional resource theories

these theories posit that we have only a fixed amount of attention and that this resource is divided up as is required in a given situation.

divided attention

trying to focus on more than one task at a time.

perceptual processes

how our mind interprets environmental stimuli.

bottom-up processing

achieving recognition of an object by breaking it down into its component parts. it relies heavily on sensory receptors.

top-down processing

relies on prior experience with an object.

visual perception

how we perceive depth, size, shape and motion.

monocular depth cues

we need only one eye to see these cues.

relative size

refers to the fact that images that are farther from us project a smaller image on the retina than do those that are closer to us.

texture gradient

the patterns of distribution of objects, appear to grow more dense as distance increases.

interposition

occurs when a near object partially blocks the view of an object behind it.

linear perspective

a monocular cue based on the perception that parallel lines seem to draw closer together as the lines recede into the distance.

vanishing point

the point at which the two lines become indistinguishable from a single line, and then disappear.

ariel perspective

a perceptual cue based on the observation that atmospheric moisture and dust tend to obscure objects in the distance more than they do nearby objects.

relative clarity

a perceptual clue that explains why less distinct, fuzzy images appear to be more distant.

motion parallax

the difference in the apparent movement of objects at different distances, when the observer is in motion.

binocular depth cues

rely on both eyes viewing an image.

stereopsis

refers to the three-dimensional image of the world resulting from binocular vison.

retinal convergence

a depth cue that results from the fact that your eyes must turn inward slightly to focus on near objects- the closer the object, the more the eye turns inwards

binocular disparity

results from the fact that the closer an object is, the less similar the information arriving at each eye will be.

Eleanor Gibson and RIchard Walk

researchers who developed the visual cliff to test depth perception.

visual cliff

a glass tabletop that appeared to be clear on one side and had a checkerboard design visible on the other side.

Gestalt approach

this view holds that most perceptual stimuli can be broken down into figure-ground relationships.

proximity

the tendency to see objects near to each other as forming groups.

similarity

the tendency to prefer to group like objects together.

symmetry

the tendency to perceive preferentially forms that make up mirror images.

continuity

the tendency to perceive preferentially fluid or continuous forms, rather than jagged or irregular ones.

closure

the tendency preferentially to close up objects that are not complete.

law of Pragnanz

law that states we tend to see objects in their simplest forms.

feature detector approach

posits that organisms respond to specific aspects of a particular stimulus.

constancy

we know that a stimulus remains the same size, shape, brightness, weight, and/or volume even though it does not appear to.

motion detection

we perceive motion through two processes: one records the changing position of the object as it moves across the retina; the other tracks how we movie our head to follow the stimuli.

apparent motion

the appearance of movement

phi phenomenon

an example includes blinking lights on a roadside arrow- they give the appearance of movement.

stroboscopic effect

an example when still pictures move fast enough to imply movement.

autokinetic effect

example: still light that appears to twinkle in darkness.

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