sensation & perception copyright © allyn and bacon 2007 this multimedia product and its...

Sensation & Perception

Copyright © Allyn and Bacon 2007

This multimedia product and its contents are protected under copyright law. The following are prohibited by law:

•Any public performance or display, including transmission of any image over a network;

•Preparation of any derivative work, including the extraction, in whole or in part, of any images

•Any rental, lease or lending of the program.

• ISBN: 0-131-73180-7

The story of JonathanThe story of Jonathan


IT’S ALL IN YOUR HEAD!!!!!!!!Color is “perception”

ELECTROMAGNETIC SPECTRUMELECTROMAGNETIC SPECTRUM


Sensation and PerceptionSensation and Perception

Sensation – Transformation of physical info from the senses into electrical (nerve) impulses

Perception –A process that makes sensory patterns meaningful and more elaborate-how the brain interprets this info.


I. How Does StimulationI. How Does StimulationBecome Sensation?Become Sensation?


The brain senses the world indirectly because the sense

organs convert stimulation into the language of the nervous system: neural impulses-it’s

different for everyone-my green isn’t exactly your green!

A. TransductionA. Transduction

Transduction – Transformation of one form of energy into another – especially the transformation of stimulus information into nerve impulses

Receptors –Specialized neurons that are activated by stimulation and transduce (convert) it into a nerve impulse


TransductionTransduction

Sensory pathway – Bundles of neurons that carry information from the sense organs to the brain


Sensory AdaptationSensory Adaptation

Sensory adaptation – Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while


ThresholdsThresholds

Absolute threshold – Amount of stimulation necessary for a stimulus to be detected

Difference threshold – Smallest amount by which a stimulus can be changed and the difference be detected (also called just noticeable difference – JND)


Subliminal??Subliminal??

• Anything below the absolute threshold


LINK

Subliminal PersuasionSubliminal Persuasion

What is it?

Studies have found that subliminal words flashed briefly on a screen can “prime” a person’s later responses

No controlled research has ever shown that subliminal messages delivered to a mass audience can influence people’s buying habits


• Vision: A single candle flame from 30 miles on a dark, clear night

• Hearing: The tick of a watch from 20 feet in total quiet

• Smell: 1 drop of perfume in a 6-room apartment

• Taste: 1 teaspoon sugar in 2 gallons of water

• Touch: The wing of a bee on your cheek, dropped from 1 cm


ThresholdsThresholds

Weber’s law – The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low

-You are more likely to notice a 5 degree increase in air temperature from 72-77, than you are from 92-97.

-Examples from other senses?


Signal Detection TheorySignal Detection Theory

Signal detection theory – Perceptual judgment as combination of sensation and decision-making processes


Stimulus eventStimulus event

Neural activityNeural activity

Comparison with Comparison with personal standardpersonal standard

Action (or no action)Action (or no action)

In other words, you compare info received from the physical world w/ what’s already in your head!

Signal Detection allows the mind to Signal Detection allows the mind to work quickly. Feature extraction is an work quickly. Feature extraction is an

example of this. example of this.


Volunteer? Pictionary is a great Volunteer? Pictionary is a great example of signal detection theory and example of signal detection theory and

feature extraction feature extraction


What color is the opposite of black?What color is the opposite of black?


Old McDonald had a what?

What do cows drink?

How Are the Senses Alike? How Are the Senses Alike? How Are They Different?How Are They Different?


The senses all operate in much the same way, but each extracts different information

and sends it to its own specialized processing region

in the brain

The Anatomy of Visual SensationThe Anatomy of Visual Sensation


Fovea – Area of sharpest vision in the retina

Retina – Light-sensitive layer at the back of the eyeball

Photoreceptors – Light-sensitive cells in the retina that convert light energy to neural impulses

Rods – Sensitive to dimlight but not colors

Cones – Sensitive tocolors but not dim light

The Anatomy of Visual SensationThe Anatomy of Visual Sensation

Visual cortex –Part of the brain – the occipital cortex – where visual sensations are processed


Color –Psychological sensation derived from the wavelength of visible light – color, itself, is not a property of the external world

Neural Pathways in the Human Visual Neural Pathways in the Human Visual SystemSystem


Transduction of Light in the RetinaTransduction of Light in the Retina


Blind SpotBlind SpotClose your right eye and look at the Close your right eye and look at the

cross w/ yo left eye.cross w/ yo left eye.


Sausage finger effect. Sausage finger effect.


VISIONVISION


AfterimagesAfterimages

Afterimages – Sensations that linger after the stimulus is removed

In the following slide, fix your eyes on the dot in the center of the flag



Negative afterimages are caused when the eyes lose sensitivity from over stimulation . Normally the eye deals with this problem by rapidly moving the eye small amounts, The motion later being "filtered out" so it is not noticeable. However if the color image is large enough that the small movements are not enough to change the color under one area of the retina, those cones will eventually tire or adapt and stop responding. When the eyes are then diverted to a blank space, the adapted photoreceptors send out little signal and those colors remain muted. However, the surrounding cones that were not being excited by that color are still "fresh", and send out a strong signal. The signal is exactly the same as if looking at the opposite color, which is how the brain interprets it.

Theories of Color Vision -Theories of Color Vision -

• The Opponent Process Theory

– red - green

• when red is active green is inhibited and vice versa

– blue - yellow

• when blue is active yellow is inhibited and vice versa

– color after images

• perception of color that is not really present; occurs after viewing the opposite or complimentary color

How the Visual System Creates ColorHow the Visual System Creates Color

Color blindness – Vision disorder that prevents an individual from discriminating certain colors


Brightness – Sensation caused by the intensity of light waves

How the Visual System Creates How the Visual System Creates BrightnessBrightness


WavelengthWavelength

ColorColor

Intensity Intensity (amplitude)(amplitude)

BrightnessBrightness

Color BlindnessColor Blindness


What numbers do you see revealed in the patterns of What numbers do you see revealed in the patterns of dots below? dots below?


about 12 - 20 percent (depending on whose figures you want to believe) of the white, male population and a tiny fraction

of the female population

• Color blindness is a result of certain cones misinterpreting the wavelengths that correspond to their respective colors. Red, green and blue colors have corresponding wavelengths. If the green cones, for example, only respond to slightly longer wavelengths, green will be interpreted by the brain as red.


Hearing: If a Tree Falls in the Hearing: If a Tree Falls in the Forest...Forest...

The Physics of SoundFrequency –

Number of cycles completed by a wave in a given amount of time


Low Frequency High Frequency

Hearing: If a Tree Falls in the Hearing: If a Tree Falls in the Forest...Forest...

The Physics of Sound


High Amplitude Low Amplitude

Amplitude – Physical strength of a wave

How Sound Waves Become Auditory How Sound Waves Become Auditory SensationsSensations


Tympanic membrane –The eardrum



Cochlea –Where sound waves are transduced



Basilar membrane –Thin strip of tissue sensitive to vibrations

Cochlea



Auditory nerve –Neural pathway connecting the ear and the brain


Auditory cortex – Portion of the temporal lobe that processes sounds


The Psychology of Pitch,The Psychology of Pitch,Loudness, and TimbreLoudness, and Timbre

Pitch – Sensory characteristic of sound produced by the frequency of the sound wave

Loudness – Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave

Timbre – Quality of a sound wave that derives from the wave’s complexity


DeafnessDeafness

Conduction deafness –An inability to hear resulting from damage to structures of the middle or inner ear

Nerve deafness –An inability to hear, linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brain, usually involving the auditory nerve or higher auditory processing centers


Position and MovementPosition and Movement

Vestibular sense –Sense of body orientation with respect to gravity

Kinesthetic sense –Sense of body position and movement of body parts relative to each other


smellsmell

• How are taste and smell related?


SmellSmell

Olfaction –Sense of smell

Olfactory bulbs –Brain sites of olfactory processing

Pheromones –Chemical signals released by organisms to communicate with other members of the species


SmellSmell


TasteTaste

Gustation – The sense of taste


Taste buds –Receptors for taste (primarily on the upper side of the tongue)

Bottom-Up andBottom-Up andTop-Down ProcessingTop-Down Processing

Bottom-up processing – Analysis that emphasizes characteristics of the stimulus, rather than internal concepts

Top-down processing – Emphasizes perceiver's expectations, memories, and other cognitive factors


PainPain

Placebos –Substances that appear to be drugs but are not

Placebo effect –A response to a placebo caused by subjects’ belief that they are taking real drugs

Pain is in the brain!!


startstart


The Skin SensesThe Skin Senses

Info the skins sends the brain:

1. Temperature

2. Texture

3. Pressure

-Extremes and tissue damage send “pain” messages to brain-brain’s way of protecting the body- “Don’t do that ya dope!”


What is the RelationshipWhat is the RelationshipBetween PerceptionBetween Perception

and Sensation?and Sensation?

Percept – Meaningful product of a perception

-What you perceive to be, not what is.

-Example of Phantom Limb Pain.


Factors influencing pain perceptionFactors influencing pain perception


62

Biopsychosocial Influences on Biopsychosocial Influences on painpain

1. Location1. Location


AGEAGE


GENDERGENDER


FATIGUEFATIGUE


MEMORY/EXPECTATIONSMEMORY/EXPECTATIONS


FOCUSFOCUS


69

Gate-Control TheoryGate-Control Theory

Melzak and Wall (1965, 1983) proposed that Melzak and Wall (1965, 1983) proposed that our spinal cord contains neurological our spinal cord contains neurological

“gates” that either block pain or allow it to “gates” that either block pain or allow it to be sensed.be sensed.

Gary C

omer/ PhototakeU

SA.com

70

Pain ControlPain Control

Pain can be controlled by a number of Pain can be controlled by a number of therapies including, drugs, surgery, therapies including, drugs, surgery,

acupuncture, exercise, hypnosis, and even acupuncture, exercise, hypnosis, and even thought distraction.thought distraction.

Todd R

ichards and Aric V

ills, U.W

. ©

Hunter H

offman, w

ww

.vrpain.com

Cultural Influences on PerceptionCultural Influences on Perception


B

A

Which box is bigger, A or B?

What is the RelationshipWhat is the RelationshipBetween PerceptionBetween Perception

and Sensation?and Sensation?


Perception brings meaning to sensation, so perception

produces an interpretation of the external world, not a

perfect representation of it

Perceptual ConstanciesPerceptual Constancies

Perceptual constancy – Ability to recognize the same object under different conditions, such as changes in illumination, distance, or location

-A shortcut the brain uses so it doesn’t have to reprocess information.


Perceptual ConstancyPerceptual Constancy


Without this process, it would take a very long time to figure out that there is an apple in each picture.

PerceptionPerception

• physical sensation interpreted in the light of experience


Perceptual Ambiguity and Distortion-Perceptual Ambiguity and Distortion-The Gestalt PsychologistsThe Gestalt Psychologists

Illusions – Demonstrably incorrect experience of a stimulus pattern, shared by others in the same perceptual environment

Ambiguous figures – Images that are capable of more than one interpretation


The Machinery ofThe Machinery ofPerceptual ProcessingPerceptual Processing

Feature detectors – Cells in the cortex that specialize in extracting certain features of a stimulus

Binding problem – A major unsolved mystery in cognitive psychology, concerning the physical processes used by the brain to combine many aspects of sensation to a single percept-


Gestalt TheoryGestalt Theory

• Pragnanz

• German for conciseness: which says that we tend to order our experience in a manner that is regular, orderly, symmetric, and simple.


Gestalt=HolisticGestalt=Holistic


The Gestalt ApproachThe Gestalt Approach

Gestalt psychology – View that much of perception is shaped by innate factors built into the brain

Figure – Part of a pattern that commands attention

Ground – Part of a pattern that does not command attention; the background


The Gestalt Laws of Perceptual The Gestalt Laws of Perceptual GroupingGrouping


SimilaritySimilarity

ProximityProximity

ContinuityContinuity

Common fateCommon fate

ClosureClosure

SymmetrySymmetry

Meaningfullness/Meaningfullness/FamiliarityFamiliarity

Gestalt principles of Gestalt principles of Perceptual OrganizationPerceptual Organization

• Closure

http://daphne.palomar.edu


• Similarity

http://www.aber.ac.uk


• http://www.aber.ac.uk

Proximity

symmetrysymmetry



• Good continuation

what most people would see

not this

http://www.aber.ac.uk

Common fateCommon fate

Meaningfulness/familiarityMeaningfulness/familiarity


Perceptual IllusionsPerceptual Illusions


Do you see or ?

Necker cube from ch. 1.

Law of PrägnanzLaw of Prägnanz


ABIRD

IN THETHE HAND

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