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Myers’ PSYCHOLOGY

Chapter 6

Perception

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Sensation & Perception

• Sensation- Process by which sensory receptors and

nervous system receive and represent stimulus energy (+1)

• Perception- Process of organizing and interpreting

sensory information to recognize meaningful objects and events

- Subject to host of psychological influences (+2)

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Visual Information ProcessingC6:4

Hastorf & Cantril (1954)• Classic case study on role of values in perception. Selective perception of

1951 football game between Dartmouth and Princeton. Princeton won. A very rough game, many penalties. Princeton quarterback, All-American in last college game, left in 2nd quarter with broken nose and mild concussion. In 3rd quarter Dartmouth quarterback's leg broken.

• A week later, Hastorf and Cantril had Dartmouth and Princeton psychology students fill out questionnaire, and authors analyzed answers of those who had seen either the game or movie of game. Two other groups viewed film of game and tabulated number of infractions seen.

• Question: "Which team do you feel started the rough play?"Pr Da Both Neither/No Answer

Dartmouth Students 2 36 53 9Princeton Students 0 86 11 3

• Question: "Do you believe game was clean and fairly played or unnecessarily rough and dirty?"

C&F R&F R&D Don’t KnowDartmouth Students 13 39 42 6Princeton Students 0 3 93 4

• When shown film, Princeton students "saw" Dartmouth team make over 2x as many infractions as were seen by Dartmouth students.

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Perception Outline

• Selective Attention

• Perceptual Illusions

• Perceptual Organization

- Form Perception

- Depth Perception

- Motion Perception

- Perceptual Constancy

• Perceptual Interpretation

- Sensory Deprivation and Restored Vision

- Perceptual Adaptation

- Perceptual Set

- Perception and the Human Factor

• Is there Extrasensory Perception?

- Claims of ESP

- Premonitions or Pretensions?

- Putting ESP to Experimental Test

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Attention: Theoretical Issues

• Attention: ability to perceive part of environment, and ignore rest

• Number of fundamental issues

- Early vs. Late selection

- Mechanisms (analogies)

• Attention as Filter

• Attentional Spotlight

• Attention as Limited Resource

- Do unattended stimuli have an influence?

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Attention: Findings

• Binocular Rivalry

• Ambiguous stimuli- Necker Cube,

Old/Young Woman, ...

• Consciously experience only one object at a time

• Attention a limited capacity system

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Necker Cube

X

• Box on left can be seen in two ways

- By one interpretation, X is at center of front wall, which faces down to left

- By other interpretation, X is at center of back wall, and front wall faces up to right

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Old or Young Woman?

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Auditory Attention Findings

• Cocktail Party Effect

- Dichotic Listening or Shadowing task

• Hear two different messages in headphones, one to each ear (+1)

- What known about message to ignored ear?

• Identify gender, loudness

• Not language, content

• But something particularly salient (e.g., your name) may be noticed

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Shadowing TaskC6:12

Selective Attention: Stroop

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C6:13Fascinating Finding

• Neisser basketball game film- Unaware of woman with

umbrella crossing screen or even person in ape suit

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Change BlindnessChange Blindness: People fail to notice pronounced changes inperceptual stimuli, evenintroduction of completely different person into conversation

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Subliminal Perception

• Can unattended stimuli affect us?

• Natural “observations”or myths

- Eat Popcorn / Drink Coca-Cola Hoax

• Denied by owner, Factual errors

• 1/24th sec duration not subliminal

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Subliminal Experimental Studies

• Shadowing messages, heard tunes in other ear

- Recognition at chance level

- Implicit memory (familiarity) > chance

• Processing ambiguous stimuli

- Homonyms: We stood by the bank.

- Affected by context in unattended ear: river, money

• Salient stimuli

- If someone at loud party says your name, then you attend ... but how? Name must have “registered” at some, subliminal level.

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Perception Outline

• Selective Attention

• Perceptual Illusions

• Perceptual Organization

- Form Perception

- Depth Perception

- Motion Perception

- Perceptual Constancy

• Perceptual Interpretation

- Sensory Deprivation and Restored Vision

- Perceptual Adaptation

- Perceptual Set

- Perception and the Human Factor

• Is there Extrasensory Perception?

- Claims of ESP

- Premonitions or Pretensions?

- Putting ESP to Experimental Test

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Illusions• Perceptual illusions

- Many based on interplay between visual stimulation and contextual cues (e.g., about distance)

- Can involve quite complex “computations” that we are unaware of

- Vertical-Horizontal Illusion

• St. Louis landmark

• Vertical=Horizontal

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Size/Distance Illusion

• Small figure at front is same size as figure at back, as are two arrows. Front figures appear much smaller. If figures dragged from back to front, would appear to shrink.

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Size & Ponzo Illusions

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PonzoIllusion

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Muller-Lyer Illusion

ABBC

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Muller-Lyer Illusion• Inward pointing

arrows appear on edges extending towards us

• Outward pointing arrows appear on edges receding away

• 2 lines, same image on retina; one (>--<) appears further away than other (<-->) must be longer. Seen as so!

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Perceptual Illusions

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C6:25Ames Room: Size-Distance Relation

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Perception Outline

• Selective Attention

• Perceptual Illusions

• Perceptual Organization

- Form Perception

- Depth Perception

- Motion Perception

- Perceptual Constancy

• Perceptual Interpretation

- Sensory Deprivation and Restored Vision

- Perceptual Adaptation

- Perceptual Set

- Perception and the Human Factor

• Is there Extrasensory Perception?

- Claims of ESP

- Premonitions or Pretensions?

- Putting ESP to Experimental Test

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Form Perception

• Gestalt

- An organized whole

- Tend to integrate pieces of information into meaningful wholes

• Figure-Ground

- Perceive objects against background

- Illustrated on next few slides

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Form: Figure Ground

• Grouping of elements and other processes lead to classification of shapes as figures and ground

- Figure: coherent, structured object

- Ground: background, context for objects

• Gestalt principles applied to figure-ground problem

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Figure-Ground Gestalt principles

• Closure: prefer shape that is closed as figure

• Relative size: see smaller shape as “figure”against larger “ground”

• Surroundedness: Figure / Ground effects enhanced if ground shape surrounds figure

• Symmetry: symmetry enhances grouping and perception of figure

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Ambiguous Vase/Faces

• Figure and Ground

- Organization of visual field into objects (Figures) that stand out from their surroundings (Ground)

- In ambiguous Figure / Ground stimuli, ambiguous which part is figure and which ground

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Figure/Ground: Ambiguous Images

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Grouping

• Gestalt Laws: principles that govern / describe how perceptual system groups together stimulus pieces in environment (see below and next few slides)

- 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

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Gestalt principle: Proximity

• Proximity one of most important factors for perceptual organization

• Here elements grouped as columns, dots, and rows depending on spacing (proximity)

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Gestalt principle: Similarity

• Things that look similar tend to be grouped together

• The “dots” image now appears to be rows

• What makes images “similar” is empirical issue

- In circular image task is to identify odd quadrant of circle, easier for leftmost of two images: distinctiveness?

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Gestalt principle: Continuity

• Left we see straight line figure as two separate lines crossing at ✖ rather than other configurations, such as “kissing beaks”

• Right, proximity, similarity and continuity interact to yield same image structure

✖

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Gestalt Principles: Closure

Parts of occluded objects are completed by visual system

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The Law of Common Fate

• Elements that move together seen as forming common object

- Animals may blend into background (above), until they move. Suddenly visible.

- As an example, next few slides and http://www.acs.appstate.edu/~kms/classes/psy3203/Movement/dots3.mov

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Common Fate Example - 1C6:43

Depth Perception

• Perception of Depth and Distance

- Ability to see objects in three dimensions

- Allows us to judge distance

• Motion and Depth: Kinetic Depth

• Two primary types of cues

- Binocular and Monocular Cues

- Development

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Depth Perception

• Binocular cues

- Require use of two eyes

- Retinal Disparity

• Images from the two eyes differ

• Closer object, larger the disparity (right)

- Convergence

• Neuromuscular cue

• Two eyes move inward for near objects (+1)

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Convergence

• The larger the angle represented by A and B in figure, nearer the object

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Depth Perception

• Monocular Cues

- Relative size: Smaller image more distant (+1)

- Interposition: Closer object blocks distant object (+2)

- Relative clarity: Hazy object seen as more distant (+3 +4)

- Texture: Coarse � close, Fine � distant (+5)

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Depth Perception: Relative Size

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Depth Perception: Interposition

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Depth Perception: Clarity

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Clarity and Perceived Distance

C6:51Depth Perception: Texture• Texture gradient

- Stimuli that are nearer have coarser texture.

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Depth Perception

• More Monocular Cues

- Relative height: Higher objects seen as more distant

- Relative motion (motion parallax): Closer objects seem to move faster (+1)

- Linear perspective: Parallel lines converge with distance (+2)

- Light and Shadow: Closer objects appear brighter (+3)

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Parallax

• Near objects move faster than distant objects

• Demonstration: MotionParallax

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Depth Perception: Perspective

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Monocular Cues: Shading

• Major light sources tend to come from above, so shading is another source of depth information. Objects shaded lighter on top seen as “sticking out towards us”.

• Here, crater (top) becomes mound (bottom) when picture turned upside down.

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Development of Depth Perception

Visual Cliff: Used by Gibson & Walk to study depth perception in infants and animals

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Infant on Visual Cliff

• Research on infants and animals indicates that certain cues for depth/distance are innate and do not depend on experience, whereas other cues are learned and do not operate without experience

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Culture and Depth PerceptionC6:59Motion

Perception• Size of objects

- “Looming” objects moving towards us

- Critical for various activities: driving, flying plane, catching ball, ...

• Phi phenomenon

- Apparent motion

- Similar to “common fate” example, but faster timing (+1)

• Motion illusions (above)

- Focus on dot, move head forward and backward

- Motion After-Effect

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Perceptual Constancy

• Perceptual Constancy

- Perceive objects as unchanged despite changes in retinal image

• Shape (above)

• Size

• Color (right)

• Brightness (+1)

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Brightness (Lightness) Constancy

White paper looks white whether in sunlight or shadow

Brightness viewed not in absolute terms, but relative to brightness of context. When cloud passes over, everything gets less bright and, as a result, nothing really seems to change.- See next few slides

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Relative Nature of Brightness

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Brightness ConstancyC6:65

Perception Outline

• Selective Attention

• Perceptual Illusions

• Perceptual Organization- Form Perception

- Depth Perception

- Motion Perception

- Perceptual Constancy

• Perceptual Interpretation

- Sensory Deprivation and Restored Vision

- Perceptual Adaptation

- Perceptual Set

- Perception and the Human Factor

• Is there Extrasensory Perception?

- Claims of ESP

- Premonitions or Pretensions?

- Putting ESP to Experimental Test

C6:66Sensory Deprivation and Restored Vision

• Restored vision

- Figure-Ground, sensed colours, not object identification

• Rearing animals with deprived visual input

- Color, Brightness, but not Form

- Held & Hein: vertical stripes (+1)

• Critical period for sensory development

- Rationale for corrective surgery for cataracts early (few months)

- Similar effect of cochlear implants

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Sensory Restriction

• Blakemore & Cooper, 1970

• Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.

C6:68Perceptual Adaptation

• Learning can also be studied by observing how people or animals adapt to modified perceptual experience

- e.g., surgery, distorting prisms

• Displacing goggles – contain prisms

- Humans adapt quickly given visual-motor experience with feedback

- Upside-down prism: Stratton (1896)

- Adaptation varies across species

• Some species unable to adapt: chicks

• In some species (owls), depends on early infant experience

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Perceptual Set

• Predisposition to see one thing and not another (+1)

- Expectations developed on basis of context

• Visual

- Loch Ness monster or log, space ships or clouds, ambiguous figure

• Auditory

- “Cheer Up” Satanic messages in backward tapes

- “-eel is on the wagon” “-eel is on the orange”

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Expectations and SetC6:71

Set (and Illusion)

• Does front monster appear frightened and back one ferocious?

• Actually, exactly the same expression (also same size).

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More examples of set

• Interpretation of neutral facial expression

- Prior Image Interpretation

• dead woman sad

• soup thoughtful

• playing child happy

• Play sad or happy music

- People asked to interpret homophones

• mourning/morning, die/dye, pain/pane

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- Mental representation of concepts based on past experience important for effect of set

- Myer’s discussion of schemas• Organized, mental representation of objects in external

world (e.g., face)

• Children’s schemas quite primitive, basic

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Representation of Concepts• Person without mental

concept of Dalmatian or Cow is unlikely to perceive these images as objects

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Concept Representation

Parts of occluded objects completed byvisual system. Requires representations (+1)

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Schemas for Faces• Face schemas exert influence on perception

- Below, exaggerated version of Michael J. Fox recognized better than actual image

- Inverted faces present perceptual difficulties (+1)

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Culture and Context Effects

C6:80Perception and Human Factors

• Many applied implications

- Medical Procedures

• Critical periods and corrective surgery

- Human Factors Research

• Design of instruments, appliances, etc.: Right stove below allows more “natural” interpretation of controls

• Airplane accidents (+1)

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Airplane Accidents

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Perception Outline

• Selective Attention

• Perceptual Illusions

• Perceptual Organization

- Form Perception

- Depth Perception

- Motion Perception

- Perceptual Constancy

• Perceptual Interpretation

- Sensory Deprivation and Restored Vision

- Perceptual Adaptation

- Perceptual Set

- Perception and the Human Factor

• Is there Extrasensory Perception?

- Claims of ESP

- Premonitions or Pretensions?

- Putting ESP to Experimental Test

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Is there Extrasensory Perception?

• Extrasensory Perception

- Claim that perception can occur without normal sensory input

• Telepathy: mind-to-mind communication

• Clairvoyance: perceive distant objects/events

• Precognition: perceive event in future

• Parapsychology

- The study of paranormal phenomena

• ESP

• Psychokinesis: mental bending/moving of objects

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Natural Observations of ESP• Apparent success

• Vague predictions: Nostradamus

• Chance

- Two students in different classes taught by same instructor are partners

- but, 40 x 60 = 2400 pairs of students, and many possible relationships

• Fraud, post-diction

• Little success for psychic predictions• Newspaper psychics

• Police departments

• Spontaneous visions/dreams

- Lindbergh baby: only 4/1300 dreams involved body in trees

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Experimental Studies of ESP

• Myers quote

- “A reproducible ESP phenomenon has never been discovered, nor has anyone produced any individual who can convincingly demonstrate psychic ability.”

• USA military: $20,000,000 on “psychic spies”

- Nothing to show

• Predicting coin toss

- 28,000 people predicted 110,972 tosses, 49.8% right

• Ganzfeld Procedure (+1)

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Ganzfeld Experiments

• Use sensory deprivation to minimize distractions

• Bem and Honorton (1994) review: 32% vs. 25%

- Concerns about some procedures (Susan Blakemore)

• Milton & Wiseman (1999)

- 30 follow-up studies

- No statistically significant effect

C6:87Critical Scientific Attitude

• Many such claims- e.g., therapeutic touch: energy fields that practitioners

believe are sensed and affected by energy fields of another person

• Can be VERY difficult to dissuade people- Frustrating for scientist, which can lead to dismissive tone- MANY efforts to demonstrate ESP have failed, yet still

many believers

• Scientific attitude- Extremely critical, skeptical- Important to consider and weigh ALL of evidence- Not out of negativity, but ONLY way to determine whether

ideas are valid or not is to subject them to most difficult tests possible

- Does not mean close-mindedness OR perpetual open-mindedness