myers’ exploring psychology (4th ed) chapter 4 sensation and perception james a. mccubbin, phd...

Myers’ EXPLORING PSYCHOLOGY (4th Ed)

Chapter 4

Sensation and Perception

James A. McCubbin, PhDClemson University

Worth Publishers

SensationSensation

a process by which our sensory receptors and nervous system receive and represent stimulus energy

Perception a process of organizing and interpreting

sensory information, enabling us to recognize meaningful objects and events

SensationBottom-Up Processing

analysis that begins with the sense receptors and works up to the brain’s integration of sensory information

Top-Down Processing information processing guided by higher-

level mental processes as when we construct perceptions drawing

on our experience and expectations

Sensation- Basic Principles

Psychophysics study of the relationship between

physical characteristics of stimuli and our psychological experience of them

Absolute Threshold minimum stimulation needed to detect a

particular stimulus usually defined as the stimulus needed

for detection 50% of the time

Sensation- Thresholds

Subliminal below one’s absolute threshold for

conscious awarenessDifference Threshold

the minimum difference that a person can detect between two stimuli 50 percent of the time

we experience the difference threshold as a just noticeable difference (jnd)

Sensation- Thresholds

When stimuli are detectable less than 50% of the time (below one’s absolute threshold) they are “subliminal”

0

25

50

75

100

Low Absolutethreshold

Medium

Intensity of stimulus

Percentageof correctdetections

Subliminal stimuli

Sensation- Thresholds

Weber’s Law for a difference to be perceived, two

stimuli must differ by a constant minimum percentage

Sensory adaptation diminished sensitivity as a

consequence of constant stimulation

VisionWavelength

the distance from the peak of one wave to the peak of the next

Hue dimension of color determined by

wavelength of lightIntensity

amount of energy in a wave determined by amplitude

VisionAccommodation

the process by which the eye’s lens changes shape to focus the image of objects on the retina

Retina the light sensitive inner surface of eye,

containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

VisionRods

retinal receptors that detect black, white, and gray

necessary for peripheral and twilight visionCones

receptor cells that are concentrated near the center of retina

function in daylight or well-lit conditions detect fine detail and give rise to color

sensation

The Eye

Optic nerve- nerve that carries neural impulses from the eye to the brain

Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there

Vision- Receptors

Receptors in the Human Eye

Cones Rods

Number

Location in retina

Sensitivity in dim light

Color sensitive? Yes

Low

Center

6 million

No

High

Periphery

120 million

Visual Information Processing

Feature Detectors nerve cells in the

brain that respond to specific features of the stimulusshapeanglemovement

Stimulus

Cell’s responses

Visual Information Processing

Parallel Processing processing several aspects of a

problem simultaneously the brain’s natural mode of

information processing for many functions, including vision

Visual Information Processing

Abstraction:Brain’s higher-level cells respond to combined information from feature-

detector cells

Feature detection:Brain’s detector cells respond to

elementary features-bars, edges, orgradients of light

Retinal processing:Receptor rods and cones

bipolar cells ganglion cells

Recognition:Brain matches the constructed image

with stored images

Scene

Visual Information Processing

Young-Helmholtz Trichromatic (three color) Theory the retina contains three different

retinal color receptors- one most sensitive to red, one to green, and one to blue- which when stimulated in combination can produce the perception of any color

The Three Primary Colors of Light

Color-Deficient Vision

People who suffer red-green blindness have trouble perceiving the number within the design

Visual Information Processing

Opponent-Process Theory theory that opposing retinal processes (red-green,

yellow-blue, white-black) enable color visionsome cells stimulated by green and inhibited by redothers stimulated by red and inhibited by green

Color Constancy perceiving familiar objects as having consistent

color, even if changing illumination alters the wavelengths reflected by the object

Opponent Process- Afterimage Effect

Audition Visual Capture- tendency for vision

to dominate the other senses Audition- the sense of hearing Frequency- the number of complete

wavelengths that pass a point in a given time

Pitch- a tone’s highness or lownessdepends on frequency

Audition- The Ear

Middle Ear the chamber between the

eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

Audition- The EarInner Ear

innermost part of ear, containing the cochlea, semicircular canals and vestibular sacs

Cochlea coiled, bony, fluid-filled tube in the

inner ear through which sound waves trigger nerve impulses

Touch

Skin Sensations pressure

only skin sensation with identifiable receptors

warmth cold pain

PainGate-Control Theory

theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain

“gate” opened by the activity of pain signals traveling up small nerve fibers

“gate” closed by activity in larger fibers or by information coming from the brain

TasteTaste Sensations

sweet sour salty bitter

Sensory Interaction the principle that one sense may influence

another as when the smell of food influences its taste

Body Position and MovementKinesthesis

the system for sensing the position and movement of individual body parts

Vestibular Sense the sense of body movement and

position, including the sense of balance

Perception

Gestalt an organized

whole tendency to

integrate pieces of information into meaningful wholes

Perceptual Organization

Figure and Ground organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Perceptual Organization- GestaltGrouping

the perceptual tendency to organize stimuli into coherent groups

Grouping Principles proximity- group nearby figures together similarity- group figures that are similar continuity- perceive continuous patterns closure- fill in gaps connectedness- spots, lines and areas are seen

as unit when connected

Perceptual Organization- Gestalt

Proximity Similarity

Continuity Closure Connectedness

Perceptual Organization- Gestalt Groupings

Gestalt grouping principles are at work here.

Perceptual Organization-Depth Perception

Depth Perception ability to see objects in three dimensions allows us to judge distance

Binocular cues- depend on use of two eyes retinal disparity

images from the two eyes differ closer the object, the larger the disparity

convergenceneuromuscular cuetwo eyes move inward for near objects

Perceptual Organization-Depth Perception

Monocular Cues-available to either eye alone relative size

smaller image is more distant

interpositioncloser object blocks distant object

relative clarityhazy object seen as more distant

texture coarse --> closefine --> distant

Perceptual Organization-Depth Perception

Visual Cliff

Perceptual Organization-Depth Perception

Relative Size

Perceptual Organization-Depth Perception

Interposition

Perceptual Organization-Depth Perception

Monocular Cues (continued) relative height

higher objects seen as more distant relative motion

closer objects seem to move faster linear perspective

parallel lines converge with distance relative brightness

closer objects appear brighter

Perceptual Organization-Depth Perception

Perspective Techniques

Perceptual Constancy

Perceptual Constancy perceiving objects as unchanging

despite changes in retinal imagecolorshape size

Perceptual Organization

Perceptual Organization-Muller-Lyer Illusion

Perceptual Organization- Size-Distance Relationship

Perceptual Organization-Brightness Contrast

Perceptual InterpretationPerceptual Adaptation

(vision) ability to adjust to an artificially displaced visual fieldprism glasses

Perceptual Set a mental predisposition to perceive one thing and not another

Perceptual Set-Schemas

What you see in the center is influenced by perceptual set

Perceptual Set-Schemas

Flying Saucers or Clouds?

Perception without Sensation?

Extrasensory Perception controversial claim that perception can occur

apart from sensory inputtelepathyclairvoyanceprecognition

Parapsychology the study of paranormal phenomena

ESPpsychokinesis