Chapter 4Chapter 4Sensation and PerceptionSensation and Perception

Sensation and PerceptionSensation and Perception

SensationThe process by which our sense organs receive information from the environment

PerceptionThe sorting out, interpretation, analysis, and integration of stimuli involving our sense organs and brain

Sensing the World Around UsSensing the World Around Us

Stimulus◦ Energy that produces a

response in a sense organ◦ Varies in both type and

intensity

PsychophysicsThe study of the relationship between the physical aspects of stimuli and our psychological experience of them

Sensing the World Around UsSensing the World Around Us

Absolute thresholdThe smallest intensity of a stimulus that must be present for it to be detected

Sensing the World Sensing the World Around UsAround Us

NoiseBackground stimulation that interferes with the perception of other stimuli

Noticing Distinctions Between Noticing Distinctions Between StimuliStimuli

“just-noticeable difference”

The smallest level of stimulation required to sense that a change in stimulation has occurred

Weber’s lawBasic law of psychophysics that states “a just noticeable difference is a constant proportion of the intensity of an initial stimulus

An adjustment in An adjustment in sensory sensory capacity capacity following following prolonged prolonged exposure to exposure to stimulistimuli

Sensory Adaptation

Vision: Structure of The EyeVision: Structure of The Eye

Vision: Reaching the RetinaVision: Reaching the Retina

Rods are thin, cylindricalreceptor cells highly sensitive

to light

Cones are light-sensitivereceptor cells responsible for

sharp focus and color perception, particularly in bright light

Cells of the EyeCells of the Eye

Vision: Sending the Message Vision: Sending the Message From the Eye to the BrainFrom the Eye to the Brain

Bipolar cellsReceive information directly from rods and cones and then communicates this information to ganglion cells

Ganglion cells Collect and summarize visual information, which is gathered and moved out of the back of the eyeball through a bundle of ganglion axons called the optic nerve

Do You Have a Blind Spot?

• (Everyone does! Close your right eye & stare at the X with your left eye, & then slowly move your head toward the screen. The worm will disappear!)

Vision: Processing the Visual Vision: Processing the Visual MessageMessage

Optic chiasmJuncture where the optic nerves of both eyes meet and then split

Feature detectionSome neurons in the cortex are activated only by visual stimuli of a particular shape or pattern

Color Vision and Color Color Vision and Color BlindnessBlindness

Trichromatic theory of color vision

Suggests that there are three kinds of cones in the retina, each of which responds primarily to a specific range of wavelengths

Opponent-process theory of color vision

Proposes that receptor cells are linked in pairs, working in opposition to each other

The Opponent-process The Opponent-process theory of color visiontheory of color vision

Hearing: Sensing SoundHearing: Sensing Sound

SoundThe movement of air molecules brought about by the vibration of an object

EardrumThe part of the ear

that vibrates when sound waves hit it

Middle earTiny chamber containing three

bones (stirrup, anvil, and hammer) that acts as a tiny mechanical amplifier

Hearing: Sensing SoundHearing: Sensing Sound

CochleaCoiled tube that looks

something like a snail and is filled with fluid that can vibrate in response to sound

Basilar membraneStructure that runs

through the center of the cochlea, dividing it into an upper and lower chamber

Hair cellsTiny cells

located on the basilar membrane that are bent by the vibrations entering the cochlea and transmit a neural message

Hearing: Physical Hearing: Physical Aspects of SoundAspects of Sound

FrequencyNumber of wave cycles that occur in a second

PitchCharacteristic of the sound that makes sound high or low

AmplitudeFeature of wave patterns that allows us to distinguish between loud and soft sounds

DecibelsMeasurement of the intensity of the sound within our range of hearing

Hearing: Sorting Out Theories of Hearing: Sorting Out Theories of SoundSound

Place Theory of HearingDifferent areas of the basilar membrane respond to different frequencies

Frequency Theory of Hearing

The entire basilar membrane acts like a microphone, vibrating as a whole in response to a sound

BalanceBalanceSemicircular canals

Structures of the inner ear consisting of three tubes containing fluid that sloshes through them when the head moves, signaling rotational or angular movement of the brain

OtolithsTiny, motion-sensitive crystals that sense bodily acceleration and gravity within the semicircular canals

SmellSmell

Olfaction◦ Can detect more than 10,000

different smells◦ Can identify gender by smell◦ Can evoke memories

Olfactory cellsReceptor cells of the nose

PheromonesPollen-like chemicals that are

released by non-humans that have an effect on other’s behavior

Taste: GustationTaste: Gustation

Taste buds◦Receptor cells located

within the tongue, as well as other parts of the mouth and throat

◦Constantly reproduce every 10 days

◦“Supertasters” v “Nontasters”

Bitter

Sour

Salty

Sweet and Fatty

The Skin SensesThe Skin Senses

Touch, pressure, temperature, and pain

Gate-Control Theory of pain

Particular nerve receptors in the spinal cord lead to specific areas of the brain related to pain

Managing PainManaging Pain

Strategies to fight pain

◦Medication◦Nerve and Brain stimulation◦Light therapy◦Hypnosis◦Biofeedback and Relaxation Techniques◦Surgery◦Cognitive Restructuring

Gestalt Laws of OrganizationGestalt Laws of Organization

FigureThe object being perceived

GroundThe background or spaces within the object

The Gestalt Laws of The Gestalt Laws of OrganizationOrganization

Organization: Gestalt Principles

Perceptual OrganizationPerceptual Organization

n Feature Analysis An approach that considers how we perceive a An approach that considers how we perceive a

shape, shape, pattern, object, or scene by reacting first to the pattern, object, or scene by reacting first to the individual individual elements that make it upelements that make it up

Top-down processingPerception that is guided by higher-level knowledge, experience, expectations, and motivations

Bottom-up processingPerception that consists of recognizing and processing information about the individual components of the stimuli

Perceptual constancyPhenomena in which physical objects are perceived as unvarying and consistent, despite changes

• Depth Perception: ability to perceive three dimensional space & accurately judge distance

Organization: Depth Perception

Perceptual Organization: Perceptual Organization: Depth PerceptionDepth Perception

Binocular disparityThe ability of the brain to integrate the two images received from the eyes into one composite view

Monocular cuesCues that allow us to obtain a sense of depth and distance with just one eye

Binocular Cues: Retinal disparity (left) & Convergence (right)

• Do you see the cow?

Understanding Perception

• Now do you see the cow?

Understanding Perception

Perception: Outer Perception: Outer LimitsLimits

Subliminal perceptionThe perception of messages about which we have no awareness

Extrasensory perception (ESP)