psy 323 – cognition chapter 10: visual imagery. visual imagery seeing in the absence of a visual...

PSY 323 – COGNITION

Chapter 10: Visual Imagery

VISUAL IMAGERY

Seeing in the absence of a visual stimulus•A type of mental imagery •The ability to recreate the sensory world in the absence of physical stimuli•Also, occurs in other senses

McCartney in 1965

Paul McCartney of “The Beatles” claimed that the song “Yesterday” came to him as a mental image

VISUAL IMAGERY

Try this: •Close your eyes and try to picture the back of a one dollar bill•Close your eyes and try to picture the front of a penny

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HOW DID YOU DO?

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EARLY IDEAS ABOUT IMAGERY

Wilhelm Wundt•Early psychologist felt that images were one of the three basic elements of consciousness (sensation and feelings were the others)•First to adopt introspection

Wilhelm Wundt(1832-1920)

Click on picture for pronunciation

IMAGELESS THOUGHT DEBATE

Much Controversy!•Over whether it is possible to have thoughts that are not accompanied by images•This debate occurred in the late 19th century and was critical to the introspectionist program because they studied imagery as a window into thought processes •If some thought was not accompanied by images, it was not clear how it could be studied

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GOOD-BYE IMAGERY…

John Watson•Father of behaviorism•“Give me a dozen healthy infants…”•Felt that the study of imagery was unproductive

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Psychology as the Behaviorist Views it. John B. Watson (1913)

(1878-1958)

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IMAGERY AND THE COGNITIVE REVOLUTION

Imagery Reenters Psychology•Refuted claims that imagery was impossible to study•Demonstrated imagery had functional role – as seen in memory tasks like paired associate learning•Key point of Paivio’s work – imagery impacts memory

Major Turning Point - Allan Paivio’s studies (1960s)

89 years old

Memory is served by two systems:

• Verbal

• Nonverbal (visual)

PAIVIO’S DUAL-CODING THEORY

PAVIO’S CONCEPTUAL-PEG HYPOTHESIS

Found concrete words easier to recall than abstract words due to imagery•Concrete nouns create mental images other words can “hang onto”

MORE EVIDENCE…

Concrete or abstract adj-noun pairsSquare-door, rusty-engineSubtle-fault, absolute-truth

Free-recall (recall as many as possible)Concrete > Abstract

Paired-Associate Learning (Square ____?)Concrete performance improved over free

Abstract performance did not

Begg (1972)

DEMONSTRATING THAT IMAGERY EXISTS

Shepard & Metzler (1971) Procedure•Mental chronometry Task: participants saw two objects, had to indicate quickly whether the two objects were the same or different

Stimuli used in mental rotation experiment

DEMONSTRATING THAT IMAGERY EXISTS

Results•Time it took to indicate that they were the same object was directly related to how far the object had to be rotatedInterpretation •Imagery and perception share some of the same mechanisms

Note: First experiment to use quantitative methods in the study of imagery.

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Shepard & Metzler (1971)

IMAGERY AND PERCEPTION

Major question: Do imagery and perception share the same mechanisms?Kosslyn (1973)Procedure•Task: Memorize an image, then answer questions about whether certain parts appear in the image•Time it takes to say yes is related to distance between initial focus and correct part

Stimulus for image-scanning experiment

IMAGERY AND PERCEPTION

Results•It took longer for participants to find parts that are located farther from the initial point of focusInterpretation •Evidence a spatial nature of imagery existed•They were scanning across the image of the object so it makes sense that parts located further away would take them longer to get to

Kosslyn (1973)

IMAGERY AND PERCEPTION

Alternative Interpretation Lea (1975)•Proposed that as participants scanned, they may have encountered other interesting parts, such as the cabin, and this distraction increased their reaction time

Kosslyn (1973)

IMAGERY AND PERCEPTION

Alternative Interpretation Lea (1975)•Proposed that as participants scanned, they may have encountered other interesting parts, such as the cabin, and this distraction increased their reaction time

Kosslyn (1973)

IMAGERY AND PERCEPTION

Kosslyn et al. (1978)Procedure•Task: Memorize an image, then answer questions about whether certain parts appear in the image•Time it takes to say yes is related to distance between initial focus and correct part

Island used in image-scanning experiment

MENTAL SCANNING(KOSSLYN ET AL. 1978)

Mental scanning time

Physical distance between locations

Results•Participants scanning times were linearly related to the physical distances between locationsInterpretation •It wasn’t the distractions; spatial nature of imaging was the reason

IMAGERY DEBATE: IS IMAGERY SPATIAL OR PROPOSITIONAL

Kosslyn’s experiments were convincing, but there was yet another alternative explanation

Pylyshyn (1973) •Felt results are based on propositional mechanisms, not on spatial representation•Mental images are created by the same mechanism that creates language•Ushered in the imagery debate (still going on)

IMAGERY DEBATE: IS IMAGERY SPATIAL OR PROPOSITIONAL

Basic idea: just because the experience is spatial doesn’t mean the underlying representation is•Spatial experience of mental images could be an epiphenomenon •Information could be encoded with language (propositional representation) or with images (depictive representations) – can’t tell

HOW DOES PHLYSHYN EXPLAIN KOSSLYN’S FIRST SET OF

RESULTS?Tacit-knowledge explanation•People in the mental scanning task behave based on what happens in a real scene•Participants unconsciously use knowledge about the world in making judgments •In the real world it takes longer to travel greater distances•Simulate this behavior in the experiment

AGAINST PROPOSITIONAL REPRESENTATION

Finke & Pinker (1982)Procedure•Short presentation of simple display with 4 random dots, followed (after 2-sec delay) by an arrow•Participants had to say whether the arrow pointed to one of the dots in the first display (gone now)

See next slide

DEMO OF FINKE & PINKER (1982)

AGAINST PROPOSITIONAL REPRESENTATION

Results•Longer responses for greater distancesInterpretations•No time to convert to propositions, no meaning in the dots (except spatial relations)

SIZE IN THE VISUAL FIELD

As you move closer to objects in the real world:

• Object fills more of your visual field• Details are easier to see

Kosslyn (1978) used these facts to investigate mental imagery

Stimuli used in this experiment

SIZE IN THE VISUAL FIELD

ProcedureTask: Imagine two objects, moving close enough so that the bigger object fills most of visual fieldAnswer questions about one of the animals

Question about the animal when it was bigger than the other animal

Question about the animal when it was smaller than the other animal

Kosslyn (1978)

Participants were asked to imagine animals, such as an elephant and a rabbit next to each other.

The experimenter asked “Does a rabbit have whiskers?”

RT = 2.020 ms

Participants were asked to imagine animals, such as a fly and a rabbit next to each other.

The experimenter asked “Does a rabbit have whiskers?”

RT = 1.870 msKosslyn (1978)

Results

SIZE IN THE VISUAL FIELD

Interpretation•Since participants answered the question about the rabbit more rapidly when it filled more of the visual field, it can be inferred that mental images are spatial just like perception

Kosslyn (1978)

SIZE IN THE VISUAL FIELD

Kosslyn also asked participants to create mental images of different sizes

•Larger images activated more of V1 (early visual areas) - just like perception

Kosslyn (1978): fMRI Study

IMAGERY NEURONS

Some neurons respond to seeing certain objects•Those neurons can fire when that object is imagined in the brain

Perception

Imagery

Kreinman et al. (2000)

BRAIN IMAGING

LeBihan et al. (1993)Compared the brain areas that are activated at three times:•When a person observed perceptions of actual visual stimuli (perception)

•When the person was imagining the stimulus (imagery)•When visual stimulus was not present; no imagery was performed

BRAIN IMAGING

• LeBihan et al. (1993)• Brain activity in area V1

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APPARENTLY ITS NOT THE END OF THE DEBATE…

Pylyshyn (2001) •Argues that just as the spatial experience of mental images is an epiphenomenon brain activity can also be an epiphenomenon•Posits that brain activity in response to imagery may indicate that something is happening, but may have nothing to do with causing imagery

TRANSCRANIAL MAGNETIC STIMULATION

Researcher allows a magnetic field to be applied to his skull and thus disrupt the activity of neurons in a particular region

See video clip

Video illustrates basic procedure used by Kosslyn et al. (1999)

The perception task:

Participants were asked to indicate which of the stripes in two of the quadrants was longer (e.g., are the stripes in 3 longer than stripes in 2?)

The imagery task:= the perception task, but they were asked to close their eyes and make judgments based on their mental image of the display

Kosslyn et al. (1999)

Manipulations:

TMS was directed to the visual area while participants were making judgments

TMS was directed to another part of the brain while participants were making judgments

Results

TMS slowed responses both in the imagery and perception conditions

Kosslyn et al. (1999)

TRANSCRANIAL MAGNETIC STIMULATION

Interpretation•The perception and imagery tasks are carried out by the same brain areas

Kosslyn et al. (1999)

NEUROPSYCHOLOGICAL CASE STUDIES

Removing Part of the Visual CortexFarah (2000)•Patient M. G. S•An educated young woman•Her right occipital lobe removed as treatment for a severe case of epilepsy.•The mental walk task was given before and after the operation

Mental Walk Task•She visually imagined walking toward an animal; And estimated how close she was when the image began to overflow•“Overflow” means that the mental image was too big so that she could not see the entire animal at once in her mental image

Removing Part of the Visual Cortex

Farah (2000)

Mental walk test: before and after the operation.

Before the operation, she could mentally walk to the image of a horse within 15 feet before “overflowing”.After the operation, she could mentally walk to the image of a horse within 35 feet before “overflowing”.

Explanation:Removing part of the visual cortex reduced the size of her field of view.

The visual cortex is important for imagery

Before the operation

After the operation

Farah (2000)

OTHER CASE STUDIES

Perceptual problems are accompanied by problems with imagery•People who have lost the ability to see color due to brain damage are also unable to create colors through imagery•People who have unilateral neglect in perception also have unilateral neglect in imagery

PERCEPTUAL PROBLEMS ARE ACCOMPANIED BY PROBLEMS WITH IMAGERY

Uilateral Neglect•Brain damage to attentional centers of the brain (right parietal lobe)•Patients ignore half the visual field•Oftentimes, the left half of the visual field is ignored•Right hemisphere brain damage = Left visual field impairment

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PERCEPTUAL PROBLEMS ARE ACCOMPANIED BY PROBLEMS WITH IMAGERY

• In typical experiments with unilateral damaged patients, the patient is asked to identify objects held up• Objects on left & right: Only right object seen• Object only on the left: Left object is seen

• Almost as if right field takes precedence

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Unilateral Neglect

DOES THIS WORK FOR IMAGERY, TOO?

Unilateral neglect patients ignore half of the visual field. But what about imagery?Bisiach & Luzzatti (1978)•Researchers asked an Italian patient to imagine standing in the Piazza del Duomo in Milan (familiar to patient)

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See next slide

THE PIAZZA DEL DUOMO IN MILAN

When the patient imagined himself standing at A, he could name objects indicated by a’s.

When he imagined himself at B, he could name objects indicated by b’s.

Bisiach & Luzzatti (1978)

PERCEPTUAL PROBLEMS ARE ACCOMPANIED BY PROBLEMS WITH IMAGERY

Results•“Face north. What do you see?”

• Only describes things on his right•“Turn around. What do you see?”

• Only describes things on his right (but was on the left originally!)

Interpretation•Neglect works on imagery, too!

Bisiach & Luzzatti (1978)

DISSOCIATIONS

What does a double dissociation prove?•Perception OK, Imagery Poor

• Guariglia et al. (1993) - Unilateral neglect only for imagery, not for perception

• Farah et al. (1988) - R.M. could recognize objects and draw them, but could not draw objects from memory (requires imagery)

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NEUROPSYCHOLOGY: PERCEPTION POOR, IMAGERY

OK• Berhmann et al. (1994) - C.K. could not name

perceived objects but could draw detailed pictures from memory

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“Feather Duster”

“Rose Twig”

“Fencer’s Mask”

Drawn by C.K.

ANOTHER CASE OF DOUBLE DISSOCIATION

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CONCLUSIONS FORM THE IMAGERY DEBATE

• Imagery and perception are closely related• Some shared mechanisms; not all• fMRIs confirm this; brain activation is not complete

• Perception is stable; imagery fragile• Harder to manipulate mental images

• See image below

Chalmers & Reisberg (1985)

USING IMAGERY TO IMPROVE MEMORY

How does imagery help improve memory for two things?•Researchers investigated bizarreness and interactivity

Wollen et al. (1972)• Remember two words• Participants told to use one strategy out of

a possible four

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See next slide

USING IMAGERY TO IMPROVE MEMORY

53Wollen et al. (1972)

USING IMAGERY TO IMPROVE MEMORY

Results•Interacting > Noninteracting•Bizarre = Nonbizarre

•Bizarreness had no effect•Interactivity did

Wollen et al. (1972):

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PEGWORD TECHNIQUE

• Associate to-do items with concrete nouns

• Rhyme number words with concrete nouns• One--bun• Two--shoe• Three--tree• Four--door• Five--hive

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PEGWORD TECHNIQUE EXAMPLE

• First thing you have to do: go to the dentist• One--bun

• Associate dentist with bun

CREDITS

Some of the slides in this presentation prepared with the assistance of the following web sites:• archlab.gmu.edu/people/jthompsz/9-VisualImagery_2.ppt• http://frank.mtsu.edu/~sschmidt/Cognitive/Imagery.pdf• http://www.slate.com/articles/health_and_science/science/

2006/04/kaavya_syndrome.html• wps.prenhall.com/wps/media/objects/923/945327/9.ppt• memoryandcognition.wikispaces.com/file/.../Imagery_Ch10.p...• www.tamu.edu/faculty/.../Ch%2010%20Visual%20imagery.pp...