Memory:Mental Imagery, More evidence, Kosslyn yet again, Image Comparison

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Cognitive Psychology PSY 504

Lecture 41

Memory

Mental Imagery

Images are tools of thinking.

Many times when we are thinking about a scene an object no longer present, we experience an

image of that scene or object. People often refer to this as "Seeing in one's mind". The important

question in mental imagery is,

What is the nature of knowledge representations that underlie mental imagery?

These representations are called mental images. Much of this research has been concerned with

the types of mental processes that can be performed on spatial images.

More evidence

A very different sort of data for the difference between spatial and linear representations comes

from the research of Roland & Friberg (1985). They had subjects either mentally rehearse a word

jingle or mentally rehearse finding their way from their house and around streets in their

neighborhood.

They measured changes in blood flow in various parts of the cortex. It is apparent that different

neural regions are involved when we process verbal versus spatial information. Moreover these

appear to be the regions that are involved in the actual processing of spoken and seen material.

The occipital and temporal areas involved in the route finding task are the same areas involved in

vision. They gave these three tasks, mental arithmetic, memory scanning of a musical jingle,

imaging a walk. And they concluded that visual cortex increase in blood flow but not for mental

arithmetic or music

Goldenberg and colleagues (1987)

Subjects learned words by either listening to them or forming visual images to represent them.

Recall was better for imagery group. More blood flow to occipital lobe for imagery group. Occipital

has lot of vision areas.

Kosslyn yet again

He mentioned in his book `Image and the Brain" at The Resolution of the Imagery Debate (1994)

that Visual Buffer is where the image is projected. Attention window selects part of image in the

buffer for detailed processing. When we recall the image and realize it is decided by attention

window.

Image Comparison

Moyer in 1973 conducted an experiment. He was interested in they speed with which subjects

could judge the relative size of two months animals from the memory. For example, which is

bigger lion or Wolf? Which is bigger lion or mouse? Many people report that in making these

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judgments, particularly for the items that are similar in size, they experience images of the two

objects and seem to compare the size of the objects in their image. Moyer also asked to estimate

the absolute size of these animals

Results

He plotted the reaction time for making a mental-size-comparison judgment between two animals

as a function of the difference between the two animal estimated sizes. In general, the judgment

times decrease as the difference in estimated size increases. The graph shows that a fairly linear

relation exists between the scale on the abscissa and the scale on the ordinate. Thus, the linear

relationship in the figure means that increasing the size difference has a diminishing effect on

reaction time.

Visual comparison

Line comparison

Significantly very similar results are obtained when subjects make comparisons of actual physical

magnitudes. Johnson (1939) had subjects judge which of two simultaneously presented lines

were longer.

Results

The graphs plot subjects' judgment time as a function of the log difference in the line length.

Again a linear relation is obtained. It is reasonable to except perceptual judgments to take longer

the more similar the quantities being compared are, since discriminating accurately is more

difficult in such circumstances. The fact that similar functions are obtained when mental objects

are compared indicates that making mental comparison involves difficulties of discrimination

similar to those involved in perceptual comparisons.

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Hierarchical Structure of images

Complex images tend to be organized into pieces where each piece represents part of the whole

structure. Reed (1974) showed subject complex images and asked them to hold images of the

forms in their minds. Then the form was removed and they were showed parts of the image to

see if they would recognize them.

Subjects were able to identify forms (b) and (c) as parts of form (a) 65 percent of the item but

were successful with form (d) only 10 percent of the time. The reason for the difference was that

subject's image of form (a) consisted of parts such a forms (b) and (c) but not form (d).

Complex images can be formed from a hierarchy of a unit.

Mental Maps

Subjects' memory for maps appears to have the hierarchical structure associated with spatial

images. Consider your mental map of the map of United States. It is probably divided into

regions, and these regions into states, and cities are presumably pinpointed within the states.

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Stevens and Coupe were able to demonstrate an experiment. There were imagery Alpha and

Beta Counties, X and Y cities. Is X east or west of Y? is X north or south of Y?.

Subjects were in error 18 percent of the time on the X-Y question for the congruent maps and 15

percent for the homogenous maps, but they were in error 45 percent of the time for the

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incongruent maps. The figure is given below.

Subjects were using information about the location of the counties to help them remember the city

locations. This reliance on higher order information led them to make errors; just as similar

reasoning can be lead errors in questions about North American geography.

An image can not be a picture but the distinctions between them can be frustratingly subtle. We

can perform operations on images, such as scanning, which we also can on pictures. However, it

appears that there may be two image systems, one that contains the continuasouly varying and

the one that contains the spatial information.

Two types of imagery

Research such as that just reviewed lends support to the view that imagery is spatial but not

visual in character. Farah and colleagues (1988) have made suggestion that there might be two

kinds of imagery, one that involves visual properties and one that involves spatial properties.

Two types are:

Visual properties

Visual properties involve recognition of visual objects and patterns seemed to be

performed in the temporal lobe.

Spatial properties

Spatial tasks such as location. They argued that imagery tasks that require access to

visual details will be performed in the temporal region and will show modality specific

effects.

Evidence

They gave some evidence that;

Patient with temporal damage

Problems with color

Problems with sizes

Problems with shapes

The patients were OK with mental rotation, with image scanning, and with locations.

Size and detail

Some psychologists wanted to know whether the image size can be changed because of visual

screen. In there experiment, Subjects were asked to picture an elephant. Then asked to picture a

rabbit next to the elephant. Later subjects were asked to picture a rabbit standing next to a fly.

Subjects took longer to see the features in a rabbit standing next to the elephant than on the on

standing next to a fly.

Implications

Our Mind's screen is somewhat similar to a TV screen in that it has a limited capacity. If a large

elephant fills the screen than the rabbit's image has to be small for it to be accommodated next to

the elephant. When the rabbit is next to the fly, the screen is available for a large rabbit.

More on size and detail

Next group was asked to picture a giant rabbit standing next to a tiny elephant. And then they

were showed a tiny rabbit standing next to a giant fly. This time they took longer to report

features on rabbit next to the fly. This was done to ensure that subjective differences in images

are accounted for.

Implications

This seems to confirm the idea that images are screened in a similar fashion to TV or cinema

screens for that matter.

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People are different

Some psychologist say there is no imagery but some say images are present.

Sir Francis Galton (Darwin's cousin) worked on imagery. In 1883 he asked people to describe

various features of their breakfast table. He found that a large number of people reported no

imagery. These people were professional and intelligent.

The result of Galton was challenged. And a study published in 1965 tested Mensa members. 97%

reported vivid imagery.

Imagers vs. verbalizers

Images and linguistic things are very different.

Visual imagers show more regular breathing patterns than verbalizers when working out

problems. This could be because verbalizers use sub vocal speech.

But there is not much breathing in vision.

Imagery is not simple

It may be simplistic to assume that imagery is either present or absent. Some people may be

better than others in using imagery for recall. Others may be able to better manipulate images to

solve problems. Yet others may be better than others to generate new images for creative

purposes.

Eidetic Imagery

Eidetic Imagery refers to people's ability to see an image that is a perfect representation. If you

see a picture of a room with 12 chairs but you didn't count them at the time. Asked to look at the

image of the room and count the chairs in it, those with eidetic imagery can do a perfect count.

Anees A. Shaikh, a Pakistani psychologist in the USA has done a lot of pioneering work on

eidetic images

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