Mental Imagery

Mental Imagery

Mental imagery (varieties of which are sometimes colloquially refered to as “visualizing,” “seeing in the mind’s eye,” “hearing in the head,” “imagining the feel of,” etc.) is quasi-perceptual experience; it resembles perceptual experience, but occurs in the absence of the appropriate external stimuli. It is also generally understood to bear intentionality (i.e., mental images are always images of something or other), and thereby to function as a form of mental representation. Traditionally, visual mental imagery, the most discussed variety, was thought to be caused by the presence of picture-like representations (mental images) in the mind, soul, or brain, but this is no longer universally accepted.

Very often, imagery experiences are understood by their subjects as echoes, copies, or reconstructions of actual perceptual experiences from their past; at other times they may seem to anticipate possible, often desired or feared, future experiences. Thus imagery has often been believed to play a very large, even pivotal, role in both memory (Yates, 1966; Paivio, 1986) and motivation (McMahon, 1973). It is also commonly believed to be centrally involved in visuo-spatial reasoning and inventive or creative thought. Indeed, according to a long dominant philosophical tradition, it plays a crucial role in all thought processes, and provides the semantic grounding for language. However, in the 20th century vigorous objections were raised against this tradition, and it was widely repudiated. More recently, it has once again begun to find a few defenders.

Why Important? Self Reported Data. Evidence. Imagery and Perception. Neural Basis. Imagery and memory.

What are images used for?
1. Images have a role in motor programing.
2. Are inspected to access information from memory. (Does a frog have a long tail?)

History
Plato believed that our thoughts rely on images.
3% of people do not have the ability to form mental images. (Glaton, 1983)
Studying imagery was not considered scientific between 1913 and 1960. Interest in imagery began after the cognitive revolution.

Differences in imagery as reported by people.
1. Vivid imagery: just like seeing.
2. Images like descriptions. not at all like seeing.

Individual differences
Imagery has various components. 1. Visual Vs. Spatial. 2. generating images. 3. Maintaining images
Visual: for getting details of visual appearance (frog tail)
Spatial: useful for manipulating images (mental rotation task )

Mental images are species of internal representation.
Has depictive (picture like) and propositional representations (sentence like).

Evidence for use of images: Mental rotation, mental scanning
Mental scanning and rotation experiments provide support for images as a depictive form of representation. Imagery appears to use parts of the visual system

1. Mental Rotation
Study by Shepard and Metzler (1971)

FIGURE 1
Subjects were asked to judge whether the objects were identical. Half of the time, the two objects were identical except for orientation. The other half of the time, the objects were mirror-images, so the correct answer was “no”.
The time taken to make a “yes” judgment increased linearly as the angle of rotation between the objects increased.

This supports that fact that images are rotated in the mind through a “functional space”. The greater the degree of rotation that more time needed to complete the rotation.

2. Mental Scanning
Study by Kosslyn, Ball, & Reiser (1978). Studying a map of locations and forming an image on the map.

Subjects were asked to focus their attention at one location (“house”) and to press a button as soon as they can “see” a second named place (“beach”).The further apart the two locations, the longer it took subjects to report that they could see the second location in the image. There were no distance effects when they memorized a list of location names and had to respond whether certain words were on the list.

Interaction between mental imagery and perception

Experiments by Segal and Fusella targeting perception of faint signals of either auditory or visual sensory input show that
1. forming a visual image interfered with visual detection except when the image matched the target. (Visualizing an H made easier to see an H).
2. Forming a visual image did not interfere with detecting an auditory signal (sound)
3. Forming an image did interfere with detecting an auditory signal.

This means that visual imagery and visual perception use some of the same resources in the brain, since they interfere with each other when both tasks are done at the same time.

Imagery in blind people
It has been postulated that blind people use spatial images rather than visual images.

Study by Reisberg
Subjects were asked to image familiar objects of different sizes (car, card table, typewriter). Each object was imaged at three distances (3, 10, or 30 feet away). Blind and sighted subjects were asked to point to where the left and right sides of the objects would be.
1. All subjects produced larger angles for the larger objects.
2. Sighted subjects produced smaller angles as distance to the object increased; blind subjects did not.
3. Blind subjects appreciated the concept of spatial extent, but did not appreciate the uniquely visual property of perspective effects

BRAIN BLOOD FLOW
What can neuroscience tell us about mental imagery?

Evidence from healthy patients
fMRI results: V1 (an area dedicated to vision) is activated during visualization
TMS results: disrupting V1 with magnetic pulses causes problems with vision and with visual imagery
V1 is important both for visual perception and mental imagery
Self-described “vivid imagers” showed greater blood flow to visual areas of the brain than nonvivid imagers, while they formed mental images.

Evidence from brain damaged patients.
There is a considerable overlap between brain areas for imagery and perception.
1. Some patients with perceptual problems have parallel problems in imagery
e.g., Cannot recognize or visualize faces.
2. Unilateral neglect syndrome. Neglect of one side of his images

Imagery and Memory
Imagery improves memory. Wordlist memorization is enhanced when people are instructed to form images of the words.
Memory is better for imaginable words. Piano vs. Context.
Memory is enhanced when people from images of objects interacting.

Imagery provides a way of coding information that is different from a purely verbal description. Imaginable words can be represented in both a verbal code and a visual code. this dual code is what leads to the memory advantage. When retrieval is attempted, there are two ways of accessing the information.

Memory for pictures
People often create verbal descriptions of pictures.
When people were given verbal labels for ambiguous shapes, their drawings were influenced.

Conclusions

1. Imagery requires a combination of mechanisms (visual, spatial, image generation…), and people vary greatly in how they use images
2. Stored visual knowledge can be used in many cognitive tasks, such as finding information in memory, navigating using a mental map, and planning sequences of movements.
3. Imagery helps memory. Words that we can form images of are easier to remember than those that we cannot form images of.
3. Vision areas are also used for imagery, but the two systems do not completely overlap

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Comments
One Response to “Mental Imagery”
  1. Anonymous says:

    If a person had cerebral palsy, would that affect there ability to form vivid mental imagrey. Because I feel like I used to be able to do it really well and now it is fuzzy at best. I have a mixture of spastic and ataxic cerebral palsy and I was wondering if that was why I am having trouble. I used to be able to do it really good and sometimes I can for a brief second but now when I try to I just get the feeling that I’m visualizing withoiut actually seeing anything. I Think that here it is referred to as Images like descriptions. If this is the case are there any mental exercises I could do to help me improve my ability to visualize more vividly?

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