Cog5 lecppt chapter10

© 2010 by W. W. Norton & Co., Inc.

Visual Knowledge

Chapter 10Lecture Outline

Chapter 10: Visual Knowledge

Lecture OutlineVisual ImageryLong-Term Visual MemoryThe Diversity of Knowledge

Visual Imagery

A variety of day-to-day problems seem to require the use of visual imageryHow many windows are in your apartment?Was David in class yesterday?Will this sweater look good with your blue

pants? What is the nature of these mental

images?

Visual Imagery

Francis Galton (1883) Introspection to study mental imagery

Self-reports suggested they could inspect mental images as pictures

The participants also differed widely in the amount of detail their mental images seemed to contain. (Or were these differences in self-reporting style?)

Studies of visual imagery in the last 50 years have avoided introspection and instead asked participants to do something with their images—to read information off them or manipulate them in some way.

© 2010 by W. W. Norton & Co., Inc.

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Visual Imagery

Chronometric studiesAsk participants to manipulate the mental

imagesObserve how long these manipulations take

Visual Imagery

Kosslyn (1976) asked participants to answer yes/no questions about their mental images. Imagined cat, confirm that cats have heads faster

compared to confirming that cats have claws (mental imagery)

The reverse was true if the participants were asked to think about cats, not to imagine them (propositional knowledge)

This suggests that as the mode of representation changes, so does the pattern of information availability

Visual Imagery

Image-scanning procedure, Kosslyn et al. (1978)

Memorize this map Scan from one landmark

to another on the imagined map

Visual Imagery

Imagined distance correspondsto real distance

Thus, mental images seem to preserve the spatial layout and geometry of the represented scene.

Visual Imagery

Does a mouse have whiskers?

Visual ImageryMental-rotation task Which of these pairs is the same?

The further the distance, the longer it takes

Visual Imagery

The greater the angle,the longer the time

As if they were rotating the images in real life

Visual Imagery

Demand characterDid image-scanning and mental-rotation

experimenters somehow cue people?Even without instruction, participants still form

images

Visual Imagery

Less accurate whensignal and image are the same

More likely to wrongly choose that the stimulus matches the image when signal and image are both visual or auditory

Mental imagery seems to use perceptual mechanisms.

Visual imagery interferes with detecting dim visual stimuli, and auditory imagery interferes with detecting quiet tones.

Visual Imagery

However, if we are imagining a stimulus related to the one we are about to perceive, facilitation occurs.

ImageryCan interfere with perception (mismatching)Can facilitate perception (matching)

Visual Imagery

Occipital areas used for early visual processing Active during visual imageryPatients with unilateral neglect may also

neglect the left side of space in their mental images

Transcranial magnetic stimulation (TMS) disrupts mental imagery

Visual Imagery

Patient can only see the right side of the plaza

Patients with unilateral neglect may also neglect the left side of space in their mental images.

Visual Imagery

Patient can only see the right side of the plaza

Visual Imagery

Functional equivalence between imagery and perception.

Visual acuity higher—can see two dots

Visual acuity lower—need more space to see two dots

For both perception and imagery, acuity is greatly reduced if the dots are not in the center of vision.

Visual Imagery

People who have been blind since birth also demonstrate the same effects in mental-rotation or image-scanning tasks, with response time being proportional to the distance traveled

Thus, we need to distinguish between visual imagery and spatial imagery

Spatial imagery may be based in movement or body imagery, or it may be abstract and not tied to any one sense

Visual Imagery

Vivid imagers versus non-imagersReport seeing images betterSelf-reported “vivid imagers” perform no

differently than “non-imagers” on tasks that depend on spatial imagery.

Vivid imagers better for visual imagery

Visual Imagery

Eidetic or photographic memory Extremely rare Found in some autistic

individuals eidetic imagery

Visual Imagery

Mental images different from pictures Perception is not neutral and goes beyond the

information given Interpretations are present in images

Visual Imagery

Imagery only preserves one interpretation

Visual Imagery

Thus, images (like percepts) are organized depictions

One way to think about mental images is as a package that includes the depiction itself as well as a perceptual reference frame

For instance, the duck/rabbit image, understood as a duck, is associated with the reference frame “facing to the left”

Visual Imagery

Don’t know what this is? Close your eyes and

rotate it 90º clockwise

Visual Imagery

Sometimes putting an idea down on paper can help make a discovery that requires a change in the reference frame

Visual Imagery

Mental images Alternative to verbal descriptionSpatial layout and geometry are preservedReflect perceptual interpretation and are

associated with reference frames

Long-Term Visual Memory

What is the nature of visual imagery taken from long-term memory?


Images in long-term memory Stored in a piecemeal fashionMust activate representation of image frameElaborate on this frame Images that have more parts or detail take

longer to create


Generating three rows faster

Generating four columns slower


Long-term visual memory Image files

Recipes or instructions for how to construct an active mental image of the object or shape

May represent visual information in terms of propositions, or verbal labels


Will have more accuratememory for something that is either blue or green

Will have less accurate memory


Interpretation changes the reconstruction of the image


Which is farther south, New Orleans or Tijuana?

Which is farther north, Seattle or Montreal?


Imagery helps memory, especially with an interaction


Dual codingHigh-imagery words, for instance, can be

coded as both word and imageLow-imagery words only have a verbal code


Studies of memory for pictures illustrate ways in which long-term visual memory reflects general principles of memory, such asPrimacy and recencyEncoding specificitySchemata or generic knowledgeSpreading activation and primingFamiliarity and source memory


Schematic retrieval (Friedman, 1979) found that participants

failed to notice differences between previously seen and new pictures if both were consistent with a schema (e.g., a kitchen or barnyard)

Pictures that contained violations of a schema (e.g., kitchen with a fireplace) were readily noticed


Boundary extension Information is filled in

that was not present in the picture

The Diversity of Knowledge

Visual working memory is based in imagery and uses perceptual, spatial representations Image scanning, rotation, zooming

Visual long-term memory is based on propositional knowledge and shares many representational principles with other forms of long-term memory Spreading activation, priming, schematic knowledge

Chapter 10 Questions

1. Based on image-zooming experiments, which of the following would participants be slowest to identify in a mental image?

a) the whiskers of a cat standing alone

b) the ears of a rhinoceros positioned next to a squirrel

c) the whiskers of a cat positioned next to an ant

d) the wings of a butterfly positioned next to a hippopotamus

2. Participants answering questions about geography might erroneously claim that San Diego, California, is farther west than Reno, Nevada, when in fact Reno is farther west. This example suggests that spatial information is sometimes

a) stored in long-term memory as propositions.b) stored in short-term memory as propositions.c) stored in long-term memory using a

perceptual code.d) stored in short-term memory using a

perceptual code.

3. Which of the following is evidence that the brain areas involved in perception and mental imagery are similar?

a) using TMS to disrupt Area V1 results in parallel problems in vision and visual imagery

b) a patient suffering from neglect syndrome may neglect the left half of imagined scenes

c) stroke patients who lose the ability to see color also lose the ability to imagine color

d) all of the above

4. What is the worst description of individual differences in imagery ability?

a) Most people are able to form images.

b) Some people are good at visual imagery, and others are good at spatial imagery.

c) Within visual imagery and spatial imagery, most people have some strengths and some weaknesses.

d) Imagery ability is fairly uniform from one person to another.

5. Which of the following is evidence that some forms of imagery are spatial and not visual?

a) Blind people can complete mental-rotation experiments as quickly and accurately as sighted people.

b) There is no interference when people are asked to judge the brightness of a light while making a mental-rotation decision.

c) Patients such as L.H. may perform well on spatial imagery tasks but fail on visual imagery tasks.

d) all of the above

6. Participants are asked to form mental images of ambiguous pictures that were viewed earlier. When asked to ___ the image and then reinterpret it, they succeed.

a) imagine

b) hear the sound of

c) imagine interacting with

d) draw

7. Which of the following mental-image reinterpretations would be the HARDEST?

a) The sought-after discovery is compatible with the image’s depiction but not its reference frame.

b) The sought-after discovery is compatible with the image’s reference frame but not its depiction.

c) The sought-after discovery is compatible with both the image’s depiction and its reference frame.

d) The sought-after discovery is compatible with neither the image’s depiction nor its reference frame.