Human Cognitive Processes: psyc 345

Ch. 10 Visual imagery

Takashi Yamauchi© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)

• (Q1) How are images represented in the brain?

• (Q2) How are perception and imagery linked?

• (Q3) Are the male brain and the female brain different? If so, how?

• (Q4) Why are there many more autistic boys than girls?

• (Q1) How are images represented in the brain?

• (Q2) How are perception and imagery linked?

• Imagery

• DVD: Secrets of the mind– Ch. 10 10 min

• How many windows do you have in your house/apartment?

• How is the furniture arranged in your bedroom?

• Are an elephant’s ears rounded or pointed?

How did you find that?

• Did you navigate your rooms one by one?

• Represent images of your rooms and house, and visit each one, as in a computer game?

• visual imagery.– Experiencing a sensory impression in the

absence of sensory input.

• What is imagery for?

– In a memory test, visualizing images of words help remember more accurately.

– Many top athletes use visual imagery to enhance their athletic performance.

– People use imagery to solve problems.

• Einstein developed the theory of relativity by imagining himself traveling beside a beam of light.

• Good mathematicians are good at visualizing math problems.

Imagery and Perception

• Perception– You get physical input. And your neurons are

responding to it.

• Imagery– You don’t have physical input, but your

neurons are responding to it.

Imagery and Perception

• Do they share the same mechanism?

• How are they related?

Imagery and Perception

• Can you form imagery of – Red apple, green apple, yellow apple, – Blue apple, orange apple, purple apple

• Can you form imagery of a zebra?– Can you seen stripes in your zebra?– Can you count how many stripes the zebra

has?

Imagery debate

• How do we create mental images?

• Analogue– Mental images and perceptual images both

involve spatial analogs of the stimulus.

• Propositional– Mental images are created by the same

mechanism that creates language (propositional mechanism)

– The spatial experience of mental images are an “epiphenomenon”.

Analog Hypothesis

• Mental images are internal representations that operate in a way that is analogous to the functioning of the perception of physical objects.– Functional-equivalency hypothesis

• Coglab

• Mental rotation

Representation

• Analog vs. digital representation

Analog representation

Fig. 2.11, p.53

Example:

• Want to compare whether or not the two figures are the same.

• How do you make a judgment?

• For physical objects, you will simply rotate them, and compare them.

Same?

What is the consequence of rotation?

• The time required for comparison corresponds to the angle of rotation.

X axis: The Angular distance between two figures

Y axis: Comparison time

Mental rotation experiments

• Show two objects side by side

• Subjects were asked to determine whether the two objects were the same.

Do people rotate objects mentally?

What do you measure? What kind of results do you expect?

• Subjects’ response times for their yes-no judgments.

• Their response times should be linearly related to the angular departure of the two objects.

Experiment:

• Subjects were presented with two objects (either together or in sequence).

• Subjects judged whether or not the two objects were identical.

• Dependent measure:– Response time and accuracy

Results

The response times observed in this task were proportional to the angular departure of two shapes.

What can you say from these results?

• What do this tell you?

• Does this relate to the functional-equivalency hypothesis?

• How?

Mental scanning(Kosslyn et al. 1978)

• Ss were shown a map of an imaginary island.

• The map showed various objects (e.g hut, tree, hill,..)

• Ss studied the map until they could reproduce it from memory.

• After that, Ss were asked to picture the map and mentally scan the picture from one location (tree) to another (hill).

• When mental scanning was completed, Ss pressed a key

Mental scanning(Kosslyn et al. 1978)

Mental scanning time

Physical distance between locations

• Ss scanning times were linearly related to the physical distances between locations

Finke & Pinker (1982)

• Ss first saw (a), and then (b).

• The task was to judge if the arrow pointed to any of the dot.

• Ss took longer to respond for greater distances between the arrow and the dot.

Ss 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 = 2.030 ms

Ss 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

Implications

• Ss answered the question about the rabbit more rapidly when it filled more of the visual field.

• Mental images are spatial just like perception

Imagery and the Brain

• Compare the brain area that are activated – (1) when a person observed perceptions of

actual visual stimuli (perception)

– (2) when the person was imagining the stimulus (imagery)

• Ganis et al. (2004) First, Ss studied stimuli in a booklet (line drawings of 90 objects)

Experiment: Imagery and perception conditions were alternated.

Perception condition:

The name of a picture is presented auditorily.

Ss saw a low contrast line drawing, and answered the same question as asked in the imagery condition (such as “Is the object higher than it is wide?” )

• Ganis et al. (2004) First, Ss studied stimuli in a booklet (line drawings of 90 objects)

Experiment: Imagery and perception conditions were alternated.

Imagery condition:

Ss closed their eyes.

The name of a picture is presented auditorily.

Ss generated the corresponding visual mental image and answered a question such as “Is the object higher than it is wide?”

Frontal areas

The activation patterns appear identical

Perception Imagery Perception - Imagery

Perception Imagery Perception - Imagery

Parietal and temporal areas

The activation patterns appear identical

Perception Imagery Perception - Imagery

Occipital areas

The activation patterns appear somewhat different

Transcranial Magnetic Stimulation

• Apply a magnetic field to a skull and disrupt the activity of neurons in a particular region.

• Demo: (4:15)– http://www.youtube.com/watch?v=XJtNPqCj-

iA

The perception task:

Ss were asked to indicate whether the stripes in two of the quadrants (e.g., the stripes in 3 longer than stripes in 2?)

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

Manipulations:

TMS was directed to the visual area while Ss were making judgments.

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

Results

TMS slowed Ss’ responses both in the imagery and perception conditions.

Implications

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

Neuropsychological case studies

• Farah 2000– Patient M. G. S– An educated young woman– Her right occipital lobe removed as treatment

for a sever case of epilepsy.– The mental walk task was given before and

after the operation

• The 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.

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

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.

Unilateral neglect

• Often caused by damage to the parietal lobe.

• People with unilateral neglect pay attention to only one side of the visual field and ignore the other side of the visual field. – http://www.youtube.com/watch?v=ADchGO-

0kGo

Imagery and unilateral neglect

• Bisiach & Luzzatti (1978) tested the imagery of a patient with unilateral neglect.

• The patient imagined himself standing at one of a familiar Piazza and named the objects around the Piazza.

Fig. 9-18, p. 343

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.

Implications

• There is a strong correspondence between the physiology of mental imagery and the physiology of perception.

Dissociations Between Imagery and Perception

• Evidence for double dissociation?

Dissociations Between Imagery and Perception

• R.M.• Damage to occipital and parietal lobes• Could draw accurate pictures of objects in

front of him• Could not draw accurate pictures of objects

from memory (using imagery)

Dissociations Between Imagery and Perception

• C.K.• Inability to name pictures of objects, even

his own drawings, in front of him• He could draw objects in great detail from

memory (using imagery)

Fig. 9-19, p. 344

CK labeled (a) as a “feather duster” (the dart), “a fencer mask” (the tennis racket), and a “rose twig with thorns (the asparagus).

CK was able to draw objects from memory in rich detail

Neuropsychological Results• Evidence for a double dissociation

between imagery and perception• Indicates separate mechanisms

• Also evidence for shared mechanisms

The mechanisms of perception and imagery overlap only partially.

Perception: mostly lower visual receiving areas and some higher visual areas

Imagery: mostly higher visual areas, and some lower visual receiving areas.

(Q3) Are the male brain and the female brain different? If so, how?

(Q4) Why are there much more autistic boys than girls?

male brain vs. female brain

– Verbal abilities: female > male– Spatial abilities: male > female

Male vs. female• http://www.youtube.com/watch?

v=NoCPDvQBG5Y&feature=related

male vs. female (30 sec)• http://www.youtube.com/watch?v=of0SxqoY-

Nw&feature=related

Autism1:00

– http://www.youtube.com/watch?v=r1KQCJzKaN0&feature=related

3:02– http://www.youtube.com/watch?v=srVKHiEPVss&feature=related– http://www.youtube.com/watch?v=filK9gZw4rA

• Female brain: empathizing brain

• Male brain: systemizing brain

• Baron-Cohen (2002), Trends in Cognitive Sciences

• The extreme male brain theory of autism (by Baron-Cohen)

• Autism is an extreme expression of the male brain.

• The female brain: empathizing• F>M

– Sharing and turn-taking (F>M)– Responding empathically to the distress of other

people (F>M)– Values in relationships (F>M)– Talk about emotion (F>M)– babies look longer at faces (F>M)

• M>F– Psychopathic personality disorder (M>F)– Competition and rough tumble play (M>F)– Aggression (M>F)– Murder (M>F) (male-male homicide was 30-40 times

more frequent than female-female homicide)

• The male brain: systematizing

• M>F– Toy preference – vehicles (M>F)– 3D construction (Lego) (M>F)– Mental rotation (M>F)– Map reading (M>F)– Motoric judgments (e.g., judge which objects

are moving faster) (M>F)– engineering, math, and physics majors (M>F)

The extreme male brain theory of autism (by Baron-Cohen)

• 1 in 200 children have one of the autistic spectrum conditions.

• The sex ratio is at least 10 males to every female.

• Overrepresented in children whose parents / grand parents are engineers – (Baron-Cohen et al.; Autism, 1997, 1, 153-

163)

• Autistic children: Impaired “female brain” / impaired empathizing

• Mindreading (predicting another’s feelings)– F>M>A

• Reading the mind in the eyes (discrimination emotions from expressions in the eyes) F>M>A

• Eye contact: F>M>A• Language development (vocabulary) F>M>A• Preference for rule-based, structured, factual

information; A>M>F• Preference for constructional toys: A>M>F• Collecting: A>M>F• Obsession with closed/well-defined systems

(e.g., computers): A>M>F

Using imagery to improve memory

• Using imagery as mnemonics

• How does it help? (4:20)– http://www.youtube.com/watch?

v=L1mweFSqACU&feature=related