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 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

How did you do?

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 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

Good-bye imagery… John Watson Father of behaviorism “Give me a dozen healthy infants…” Felt that the study of imagery was unproductive Psychology as the Behaviorist Views it. John B. Watson (1913) (1878-1958)

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

Paivio’s Dual-Coding Theory Memory is served by two systems: Verbal Nonverbal (visual)

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 pairs Square-door, rusty-engine Subtle-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 Shepard & Metzler (1971) Results Time it took to indicate that they were the same object was directly related to how far the object had to be rotated Interpretation Imagery and perception share some of the same mechanisms Note: First experiment to use quantitative methods in the study of imagery.

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 focus Interpretation 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) Results Participants scanning times were linearly related to the physical distances between locations Interpretation It wasn’t the distractions; spatial nature of imaging was the reason Mental scanning time Physical distance between locations

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 distances Interpretations 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 Procedure Task: Imagine two objects, moving close enough so that the bigger object fills most of visual field Answer 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)

Results 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 ms Kosslyn (1978)

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

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)

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)

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 Cortex Farah (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

Removing Part of the Visual Cortex 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 Farah (2000)

Before the operation After the operation 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 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

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 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) 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)

Neuropsychology: Perception Poor, Imagery OK Berhmann et al. (1994) - C.K. could not name perceived objects but could draw detailed pictures from memory “Fencer’s Mask” “Rose Twig” “Feather Duster” Drawn by C.K.

ANOTHER CASE OF Double Dissociation

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 See next slide 

Using imagery to improve memory Wollen et al. (1972)

Using imagery to improve memory Results Interacting > Noninteracting Bizarre = Nonbizarre Bizarreness had no effect Interactivity did Wollen et al. (1972):

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

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...