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Sensation and Perception


Sensation and Perception Unit 3 Chapter 4 Students will explain the processes of sensation and perception and describe the interaction between the person and the ... – PowerPoint PPT presentation

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Title: Sensation and Perception

Sensation and Perception
  • Unit 3
  • Chapter 4

Basic Concepts
  • sensation- stimulation of sense organs
  • converted into neural impulses
  • perception- selection, organization, and
    interpretation of sensory input
  • meaningful experiences
  • psychophysics- study of how physical stimuli are
    translated into psychological experiences

Thresholds Looking for Limits
  • thresholds- dividing point between energy levels
    that do and do not have a detectable effect
  • absolute threshold minimum stimulus intensity
  • just noticeable difference smallest difference
    in stimulus intensity that a specific sense can

Examples of Absolute Thresholds
Sense Absolute Threshold
Vision A candle flame seen at 30 miles on a dark clear night
Hearing The tick of a watch under quiet conditions at 20 feet
Taste One teaspoon of sugar in two gallons of water
Smell One drop of perfume diffused into entire volume of a six room apartment
Touch The wing of a fly falling on your cheek from a distance of 1 centimeter
Signal Detection Theory
  • proposes that detection of stimuli involves
    decision processes as well as sensory processes,
    both influenced by variety of factors besides
    stimulus intensity
  • expectations
  • level of noise

Perception Without Awareness
  • subliminal perception- registration of sensory
    input without conscious awareness
  • below threshold
  • money, sex,
  • religion

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Sensory Adaptation
  • gradual decline in sensitivity to prolonged
  • continued exposure adaptation to stimulus
  • automatic process that keeps people tuned into
    changes rather than constants in their sensory

Our Sense of Sight The Visual System
  • Unit 3

The Stimulus Light
  • light- form of electromagnetic radiation that
    travels as a wave
  • Varies in both amplitude and wavelength
  • Amplitude affects perception of brightness
  • Wavelength affects perception of color

The Eye A Living Optical Instrument
  • cornea- provides 2/3 of eyes total power
  • lens- focuses light rays on the retina
  • retina- absorbs light, processes images, sends
    visual info to brain
  • pupil- permits light to pass into eye

Visual Receptors Rods and Cones
  • 5-6.4 million cones
  • daylight vision and color vision
  • visual acuity- sharpness and precise detail
  • RODS
  • 100-125 million rods
  • night vision and peripheral vision
  • sensitive to dim light

Visual Deficiencies
  • Nearsightedness
  • close objects seen clearly but distant objects
    appear blurry
  • light falls short of retina
  • eyeball is too long
  • Farsightedness
  • distant objects seen clearly but close objects
    appear blurry
  • light falls behind retina
  • eyeball is too short

Visual Adaptation
  • Dark Adaptation
  • process by which the eyes become more sensitive
    to light in low illumination
  • Complete in 30 minutes
  • Light Adaptation
  • process whereby eyes become less sensitive to
    light in high illumination
  • Improves visual acuity

Viewing the World in Color
  • trichromatic theory- human eye has three types of
    receptors with differing sensitivities to
    different light wavelengths
  • red, green and blue
  • color mixing allows for all colors
  • afterimage- visual image that persists after a
    stimulus is removed
  • color will be complement of original color

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Perceiving Forms, Patterns, and Objects
  • Unit 3

Perceptions are Subjective
  • same visual input can result in radically
    different perceptions
  • perceptual set- readiness to perceive a stimulus
    is a particular way
  • inattentional blindness- involves failure to see
    visible objects or events because attention is
    focused elsewhere

Looking at the Whole Picture Gestalt Principles
  • Figure and Ground
  • figure is thing being looked at, while ground is
    background against which it stands
  • figures appear closer, stand out and have more

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Gestalt Principles
  • Proximity
  • things that are near one another seem to belong

Gestalt Principles
  • Closure
  • group elements to create completeness
  • fill in gaps

Gestalt Principles
  • Similarity
  • tendency to group stimuli that are similar
  • same characteristics

Gestalt Principles
  • Simplicity
  • Tendency to group elements that combine to form a
    good figure
  • Organize forms in simplest way possible

Gestalt Principles
  • Continuity
  • follows in direction led
  • connect points that result in straight or gently
    curved lines that create smooth paths

Perceiving Depth of Distance
  • depth perception- interpretation of visual cues
    that indicate how near or far away objects are
  • Binocular Cues
  • clues about distance based on differing views of
    the two eyes
  • retinal disparity- images projected to different
    locations on right and left retinas
  • convergence- sensing the eyes converging toward
    each other as they focus on closer objects
  • Monocular Cues
  • clues about distance based on the image in either
    eye alone
  • motion parallax- images projected at different
    distances moving across retina at different rates
  • pictorial depth cues-
  • clues about distance
  • given in a flat picture

Phi Phenomenon
  • illusion of movement created by presenting visual
    stimuli in rapid succession
  • our perceptions fill in the gaps to perceive

Stroboscopic Photography
Our Sense of Hearing The Auditory System
The Stimulus Sound
  • sound waves are vibrations of molecules that
    travel through physical medium
  • wavelength described in terms of frequency
  • cycles per second, hertz (Hz)
  • amplitude described in terms of loudness
  • measured in decibels (dB)

Sensory Processing in the Ear
  • external ear
  • vibration of air molecules
  • middle ear
  • vibration of movable bones
  • inner ear
  • waves in a fluid

The human ear
  • pinna- sound collecting bone
  • hammer, anvil, stirrup- amplify tiny changes in
    air pressure
  • cochlea- contains receptors for hearing

Our Chemical Senses Taste and Smell
  • https//

Taste The Gustatory System
  • Chemical substances that are soluble
  • Receptors are clusters of taste cells on taste
  • short life of 10 days
  • perception depend on patterns from receptors
  • Four primary tastes
  • sweet, sour, salty, bitter

Smell The Olfactory System
  • chemical substances-volatile ones that evaporate
    and spread throughout the air
  • dissolved in fluid, mucus in the nose
  • olfactory cilia- hairlike structures in upper
    portion of nasal passages
  • short life (30-60 days)
  • Sensory adaptation 4 minutes

Our Sense of Touch
  • conversion of physical sensation into a
    psychological experience
  • mechanical, thermal and chemical energy
  • pressure of touch in warmth, cold and pain

Puzzles in Pain Perception
  • Pain Pathways
  • Fast- registers localized pain and relays it to
    cortex in fraction of a second
  • Slow- conveys longer lasting, aching or burning
    pain that comes after initial injury
  • Gate Control Theory
  • Incoming pain sensations must pass through gate
    in spinal cord that can be closed, blocking
    ascending pain signals
  • Cognitive and emotional processes block pain

Our Other Systems
  • Kinesthetic
  • monitors positions of various body parts
  • receptors located in joints and muscles
  • Vestibular
  • responds to gravity and keeps you informed about
    you bodys location in space
  • provides the sense of balance and equilibrium
  • receptors located within semicircular canals of