Copyright © 2010 Pearson Education Canada6-1Copyright © 2010 Pearson Education Canada Sensation...

Copyright © 2010 Pearson Education Canada 6-1Copyright © 2010 Pearson Education Canada

Sensation and PerceptionSensation and Perception

Chapter 6Chapter 6

Copyright © 2010 Pearson Education Canada 6-2Copyright © 2010 Pearson Education Canada -2

Chapter OutlineChapter Outline

• Our Sensational SensesOur Sensational Senses

• VisionVision

• HearingHearing

• Other SensesOther Senses

• Perceptual Powers: Origins and InfluencesPerceptual Powers: Origins and Influences

• Puzzles of PerceptionPuzzles of Perception

Sensation & PerceptionSensation & Perception

• SensationSensation

– The detection of physical energy emitted or reflected by The detection of physical energy emitted or reflected by physical objectsphysical objects

– Occurs when energy in the external environment or the Occurs when energy in the external environment or the body stimulates receptors in the sense organsbody stimulates receptors in the sense organs

• PerceptionPerception

– Process by which the brain organizes and interprets Process by which the brain organizes and interprets sensory informationsensory information

Copyright © 2010 Pearson Education Canada 6-3

Separate Sensations?Separate Sensations?• Sense receptorsSense receptors

– Specialized cells that convert physical energy in the Specialized cells that convert physical energy in the environment or the body to electrical energy that can be environment or the body to electrical energy that can be transmitted as nerve impulses to the braintransmitted as nerve impulses to the brain

• Dendrites of sensory Dendrites of sensory neurons responsible for neurons responsible for smell, pressure, pain, & smell, pressure, pain, & temperaturetemperature

• Specialized cells for vision, Specialized cells for vision, hearing, tastehearing, taste


Separate Sensations?Separate Sensations?

• Doctrine of specific nerve energiesDoctrine of specific nerve energies

– Principle that different sensory modalities exist because Principle that different sensory modalities exist because signals received by the sense organs stimulate different signals received by the sense organs stimulate different nerve pathways leading to different areas of the brainnerve pathways leading to different areas of the brain

– If possible, allows for If possible, allows for sensory substitutionsensory substitution

– Sensory crossover also occurs in Sensory crossover also occurs in synesthesiasynesthesia where where stimulation of one sense consistently evokes a sensation stimulation of one sense consistently evokes a sensation in anotherin another


Measuring the SensesMeasuring the Senses

• PsychophysicsPsychophysics

– Field concerned with how the physical properties Field concerned with how the physical properties of stimuli are related to our psychological of stimuli are related to our psychological experience of themexperience of them

– Commonly relies on measuring absolute Commonly relies on measuring absolute threshold, difference threshold, and applying threshold, difference threshold, and applying signal-detection theorysignal-detection theory



• Absolute thresholdAbsolute threshold

– The smallest quantity of physical energy that can be The smallest quantity of physical energy that can be reliably detected by an observer (50% of the time)reliably detected by an observer (50% of the time)

– Senses are sharp, but only tuned into narrow band of Senses are sharp, but only tuned into narrow band of physical energiesphysical energies



• Difference thresholdDifference threshold– The smallest difference in stimulation that can reliably be The smallest difference in stimulation that can reliably be

detected by an observer when two stimuli are compareddetected by an observer when two stimuli are compared– Also called Also called just noticeable difference just noticeable difference (JND)(JND)

• Signal detection theorySignal detection theory– Divides the detection of Divides the detection of

sensory signals into a sensory signals into a sensory process and a sensory process and a decision processdecision process


Sensory Adaptation & DeprivationSensory Adaptation & Deprivation

• Sensory adaptationSensory adaptation

– Reduction or disappearance of sensory responsiveness Reduction or disappearance of sensory responsiveness when stimulation is unchanging or repetitiouswhen stimulation is unchanging or repetitious

– Useful as spares us from responding to unimportant Useful as spares us from responding to unimportant informationinformation

• Sensory deprivationSensory deprivation

– The absence of normal levels of sensory stimulationThe absence of normal levels of sensory stimulation– Varied responses somewhat dependant on expectations Varied responses somewhat dependant on expectations

& interpretations (e.g., hallucinations)& interpretations (e.g., hallucinations)


Sensing Without PerceivingSensing Without Perceiving

• Selective attentionSelective attention

– Focusing of attention on selected aspects of the Focusing of attention on selected aspects of the environment and blocking out the othersenvironment and blocking out the others

• Inattentional blindnessInattentional blindness

– Failure to consciously perceive something Failure to consciously perceive something you are looking at because you are not you are looking at because you are not attending to itattending to it


VisionVision• Light stimuli (waves) have physical characteristics Light stimuli (waves) have physical characteristics

that affect three psychological dimensions of our that affect three psychological dimensions of our visual world:visual world:

1.1. HueHue– Dimension of visual Dimension of visual

experience experience specified specified by colour namesby colour names

– Related to the Related to the wavelengthwavelength of light of light


VisionVision

2.2. BrightnessBrightness– Dimension of visual experience related to the amount Dimension of visual experience related to the amount

of light emitted from or reflected by an objectof light emitted from or reflected by an object– Related to Related to amplitudeamplitude of wavelength of wavelength

3.3. SaturationSaturation– Dimension of visual experience related to the Dimension of visual experience related to the

complexity of light wavescomplexity of light waves– Vividness or Vividness or puritypurity of colour of colour


An Eye on the WorldAn Eye on the World

• Cornea: Cornea: Protects eye and Protects eye and bends light toward lensbends light toward lens

• Lens: Lens: Focuses on objects Focuses on objects by changing shapeby changing shape

• Iris: Iris: Controls amount of Controls amount of light that gets into eyelight that gets into eye

• Pupil: Pupil: Widens or dilates Widens or dilates to let in more lightto let in more light


Visual ReceptorsVisual Receptors

• RetinaRetina– Neural tissue lining the back of the eyeball’s interior, Neural tissue lining the back of the eyeball’s interior,

which contains the receptors for visionwhich contains the receptors for vision

– RodsRods: visual : visual receptors that receptors that respond to dim lightrespond to dim light

– ConesCones: visual : visual receptors involved in receptors involved in colour visioncolour vision


The RetinaThe Retina

• We experience chemical changes in rods & cones We experience chemical changes in rods & cones when our eyes adjust fully to dim illumination when our eyes adjust fully to dim illumination (called (called dark adaptationdark adaptation))

• Retinal processing also involves Retinal processing also involves ganglion cellsganglion cells

– Neurons in the retina that gather information from Neurons in the retina that gather information from receptor cells (by way of intermediary bipolar cells)receptor cells (by way of intermediary bipolar cells)

– Axons form the optic nerve which leaves the eye at the Axons form the optic nerve which leaves the eye at the optic disk (location of optic disk (location of blind spotblind spot))


Structures of the RetinaStructures of the Retina


Vision is Not Like a CameraVision is Not Like a Camera

• Visual processing is an active process & involves Visual processing is an active process & involves many types of cells in different brain regionsmany types of cells in different brain regions

– Cortical cells respond to lines of specific orientations, Cortical cells respond to lines of specific orientations, others respond to properties of shapes & arrangements others respond to properties of shapes & arrangements (e.g., spirals, faces)(e.g., spirals, faces)

• Feature detector cellsFeature detector cells– Cells in the visual cortex that are sensitive to specific Cells in the visual cortex that are sensitive to specific

features of the environmentfeatures of the environment


How We See ColourHow We See Colour

• Trichromatic theoryTrichromatic theory– Proposes three basic types of cones, each sensitive to a Proposes three basic types of cones, each sensitive to a

certain range of wavelengths (red, blue, green)certain range of wavelengths (red, blue, green)– Interaction assumed to produce all the different Interaction assumed to produce all the different

experiences of hueexperiences of hue

• Opponent-process theoryOpponent-process theory– Assumes that the visual system treats pairs of colours as Assumes that the visual system treats pairs of colours as

opposing or antagonisticopposing or antagonistic– Occurs in the ganglion cells, and neurons in thalamus & Occurs in the ganglion cells, and neurons in thalamus &

visual cortexvisual cortex


Negative AfterimagesNegative Afterimages


Constructing the Visual WorldConstructing the Visual World

• We rely on various Gestalt principles to organize We rely on various Gestalt principles to organize visual inputvisual input

• FigureFigure: item of interest : item of interest that stands out from that stands out from the rest of the the rest of the environmentenvironment

• GroundGround: environment : environment or backgroundor background


Gestalt PrinciplesGestalt Principles1.1. ProximityProximity: things near each other tend to be grouped : things near each other tend to be grouped

togethertogether

2.2. ClosureClosure: the brain fills in gaps to perceive complete forms: the brain fills in gaps to perceive complete forms


Gestalt PrinciplesGestalt Principles

3.3. SimilaritySimilarity: things that : things that are alike are perceived are alike are perceived together together

4.4. ContinuityContinuity: lines & patterns tend to be perceived as : lines & patterns tend to be perceived as continuing in time or spacecontinuing in time or space


Binocular CuesBinocular Cues

• Binocular cues Binocular cues provide visual cues to depth provide visual cues to depth or distance requiring two eyesor distance requiring two eyes

– Convergence:Convergence: the turning inward of the eyes, the turning inward of the eyes, which occurs when they focus on a nearby objectwhich occurs when they focus on a nearby object

– Retinal disparity: Retinal disparity: the slight difference in lateral the slight difference in lateral separation between two objects as seen by the separation between two objects as seen by the left eye and the right eyeleft eye and the right eye


Monocular CuesMonocular Cues

• Monocular cues Monocular cues are visual cues to depth or are visual cues to depth or distance that can be used by one eye alonedistance that can be used by one eye alone

– Light and shadow, interposition, motion Light and shadow, interposition, motion parallax, relative size, relative clarity, texture parallax, relative size, relative clarity, texture gradients, linear perspectivegradients, linear perspective

• See Pages 210-211 in your text for descriptions See Pages 210-211 in your text for descriptions and images and images


Visual ConstanciesVisual Constancies

• Another important perceptual skill is Another important perceptual skill is perceptual constancyperceptual constancy

– The accurate perception of objects as stable or The accurate perception of objects as stable or unchanged despite changes in the sensory unchanged despite changes in the sensory patterns they producepatterns they produce

– Best-studied are Best-studied are shape, location, size, shape, location, size, brightness, and colour constanciesbrightness, and colour constancies


Visual IllusionsVisual Illusions

• Our systems are sometimes Our systems are sometimes fooled when making sense fooled when making sense of the worldof the world

• Perceptual illusions give us Perceptual illusions give us information about perceptual information about perceptual strategies used by brain, strategies used by brain, and how misleading and how misleading messages are interpretedmessages are interpreted

• Many classic visual illusionsMany classic visual illusions


HearingHearing

• AuditionAudition refers to our sense of hearing refers to our sense of hearing

• Three physical characteristics of sound waves that Three physical characteristics of sound waves that alter psychological experience of sound:alter psychological experience of sound:

a)a) LoudnessLoudness: intensity/amplitude of pressure wave (dB): intensity/amplitude of pressure wave (dB)

b)b) PitchPitch: frequency of pressure waves (Hz); height or : frequency of pressure waves (Hz); height or depth of tonedepth of tone

c)c) TimbreTimbre: complexity of the pressure wave; : complexity of the pressure wave; distinguishing quality of sounddistinguishing quality of sound


An Ear on the WorldAn Ear on the World• CochleaCochlea

– Snail-shaped, fluid-filled organ in the inner ear, Snail-shaped, fluid-filled organ in the inner ear, containing the structure where the receptors for hearing containing the structure where the receptors for hearing are locatedare located

• Organ of CortiOrgan of Corti– Structure in the cochlea containing the hair cells that are Structure in the cochlea containing the hair cells that are

the auditory receptorsthe auditory receptors

• Basilar membraneBasilar membrane– Rubbery membrane that stretches across the interior of Rubbery membrane that stretches across the interior of

the cochlea in which the hair cells are embeddedthe cochlea in which the hair cells are embedded


Structures of the EarStructures of the Ear


Constructing the Auditory WorldConstructing the Auditory World

• Patterns of sound also organized to construct Patterns of sound also organized to construct meaningful patternsmeaningful patterns

• Gestalt principles can also relate to sound Gestalt principles can also relate to sound perceptionperception– e.g., Cdn researcher Bregman & “auditory scenes”e.g., Cdn researcher Bregman & “auditory scenes”

• Sound localization Sound localization – relies on loudness and – relies on loudness and intensity of stimuli to tell us where a sound is intensity of stimuli to tell us where a sound is coming fromcoming from


Taste (Gustation)Taste (Gustation)

• PapillaePapillae– Knoblike elevations on the tongueKnoblike elevations on the tongue– Contains the Contains the taste buds taste buds (taste receptor cells)(taste receptor cells)– 5 main tastes: salty, sour, bitter, sweet, umami5 main tastes: salty, sour, bitter, sweet, umami

• Genetic differences Genetic differences in amount and in amount and sensitivity of taste sensitivity of taste buds buds

• Culture, learning, & food attractiveness influence preferencesCulture, learning, & food attractiveness influence preferences


Smell (Olfaction)Smell (Olfaction)

• Receptors in Receptors in each nasal each nasal cavity respond cavity respond to chemical to chemical molecules in airmolecules in air

– Trigger Trigger reactions in reactions in olfactory bulb & olfactory bulb & higher brain higher brain regionsregions

– Detect around Detect around 10,000 smells10,000 smells


Skin SensationsSkin Sensations

• Basic skin senses: Basic skin senses:

– Touch (pressure), warmth, cold, painTouch (pressure), warmth, cold, pain– Certain spots on skin especially sensitive to 4 Certain spots on skin especially sensitive to 4

basic sensationsbasic sensations

• Pain differs from other skin sensesPain differs from other skin senses

– When stimulus producing pain is removed, the When stimulus producing pain is removed, the sensation may continue (e.g., chronic pain)sensation may continue (e.g., chronic pain)


Theories of PainTheories of Pain

• Gate-control theory Gate-control theory of pain of pain

– The experience of The experience of pain depends in part pain depends in part on whether pain on whether pain impulses get past a impulses get past a neurological “gate” neurological “gate” in the spinal cord in the spinal cord and reach the brainand reach the brain


Theories of PainTheories of Pain

• Neuromatrix theory Neuromatrix theory of painof pain

– Matrix of neurons in Matrix of neurons in the brain is capable the brain is capable of generating pain of generating pain (& other (& other sensations) in the sensations) in the absence of signals absence of signals from sensory nervesfrom sensory nerves

– Accounts for Accounts for phantom painphantom pain


The Environment WithinThe Environment Within

• KinesthesisKinesthesis

– Sense of body position and movement of body Sense of body position and movement of body parts (also called kinesthesia)parts (also called kinesthesia)

• EquilibriumEquilibrium

– Sense of balanceSense of balance– Influenced by Influenced by semicircular canalssemicircular canals: sense organs : sense organs

in the inner ear the contribute to equilibrium by in the inner ear the contribute to equilibrium by responding to rotation of the headresponding to rotation of the head


Perceptual PowersPerceptual Powers

• Is perception hard-wired or influenced by learning? Is perception hard-wired or influenced by learning?

• Inborn abilities:Inborn abilities:

– Infants born with Infants born with basic sensory basic sensory abilities which abilities which rapidly develop rapidly develop

– Depth perception Depth perception & visual cliff & visual cliff experimentsexperiments


Perceptual PowersPerceptual Powers

• Critical periods:Critical periods:

– Crucial windows of time Crucial windows of time during which a person during which a person must have certain must have certain experiences or perception experiences or perception will be impairedwill be impaired

– Classic studies with kittens Classic studies with kittens in controlled environments in controlled environments (visual perception)(visual perception)


Psychological & Cultural InfluencesPsychological & Cultural Influences

• Perception is also influenced by:Perception is also influenced by:

1.1. NeedsNeeds: more likely to perceive something when we : more likely to perceive something when we need or have an interest in itneed or have an interest in it

2.2. BeliefsBeliefs: what we believe can affect what we perceive: what we believe can affect what we perceive

3.3. EmotionsEmotions: can influence interpretations of sensory : can influence interpretations of sensory information (especially pain & fear)information (especially pain & fear)

4.4. ExpectationsExpectations: previous experiences influence what we : previous experiences influence what we perceive (e.g., perceive (e.g., perceptual setperceptual set))


Puzzles of PerceptionPuzzles of Perception

• Perceiving without awareness (Perceiving without awareness (subliminal subliminal perceptionperception))

– Visual stimuli can affect behaviour even when you are Visual stimuli can affect behaviour even when you are unaware that you saw it (unaware that you saw it (primingpriming))

– Nonconscious processes influence perception, memory, Nonconscious processes influence perception, memory, thinking, decision-makingthinking, decision-making

– Subliminal Subliminal persuasionpersuasion attempts (e.g., theatre study) attempts (e.g., theatre study) often don’t consider person’s motivation (placebo often don’t consider person’s motivation (placebo effects)effects)


Puzzles of PerceptionPuzzles of Perception

• Extrasensory perception (ESP)Extrasensory perception (ESP)

– Claims that some can send & receive messages Claims that some can send & receive messages about the world without relying on the usual about the world without relying on the usual sensory channels (limited empirical support)sensory channels (limited empirical support)

• ParapsychologyParapsychology

– Study of purported psychic phenomena such as Study of purported psychic phenomena such as ESP & mental telepathyESP & mental telepathy


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