Mental image

The imagery debate or debate about visual presentation is a classic controversy in cognitive science. For her it comes to the question of how the cognitive processes are to be described, which occur when one imagines something figuratively.

History

For centuries, was thinking about the visual presentation in the context of a picture theory of perception, see also the historical concepts of perception and the philosophy of → → schematism. The picture theory states the obvious: the incident light beams projecting an image onto the retina. This image is then decomposed and reproduced in the brain. If one accepts such a theory of perception, so it is easy to explain the mental image: The generated in the performance of mental images are also generated in the visual presentation ( without direct visual input ).

So catchy, this theory may be, it is now generally rejected: When perceiving images are created in the mind not in the literal sense, and also visual images can not be explained that way. To give only one objection: If perception is actually mediated by images in the mind, then it must ( in the head) to be someone who is looking at the pictures, otherwise they would have no purpose there. But this is the absurd idea of ​​a homunculus. But how can you ever find out what is really going on in your head? Not at all: For a long time was the answer. So it was also the consequence that behaviorism in the first half of the 20th century issues, such as rejected by the internal processes in visual idea as unscientific. The psychology of C. G. Jung treated the phenomenon of inner pictures, see a → Imago. Brain research has contributed through the detection of sensory projection centers to better understand the physiological process in the visual and pictorial images.

Pylyshyns propositional theory

This changed with the sudden development of the neuro-and cognitive sciences. Suddenly the question of the internal processes more than pure speculation was, and so the question was asked again after pictorial representation. It was mainly Stephen Kosslyn and Zenon Pylyshyn, which brought the debate in the 1970s rolling. Kosslyn put forward the theory that in the visual presentation similar processes as in perception. Pylyshyn turns up today vehemently against this thesis. This is related to Pylyshyns general idea of the workings of the mind. It assumes that information is stored in the brain in propositional form. Propositions represent the meaning of information, independent of the specific characteristics of individual information-bearing event ( so-called token ). An example:

These statements have different properties, but they are all supporting the same proposition that can be expressed for example as follows:

Proposition abstracted from the individual properties of the information carriers, and outputs the general sense again. ( This also means that 4 is not supposed to be played in one of the languages ​​of first - third, fourth must be formulated in a metalanguage. ) In terms of a uniform propositional " language of thought " is Pylyshyn assume that the idea of a red ball is stored in the form of Proposition ( 4 ), and not as an image. Pictorial elements are conceivable at most as non-functional derivatives of the propositions - that is, as epiphenomena of the premises.

Kosslyns theory visual processing

Kosslyn has now since the 70 's, experiments that are to show that the phenomenon of pictorial presentation by a propositional theory is inadequate to explain. Rather, we have to assume - as Kosslyn - that pictorial presentation essentially rests on the same principles as perception. In the following, a representative argument Kosslyns is playing:

In one experiment, two identical, three-dimensional objects in different positions are juxtaposed. The subject to decide whether or not the objects are identical. The greater the angle of rotation necessary to bring the objects in coverage, the longer the person to answer the question. It seems clear that the people of the objects need to rotate in the imagination. If the idea is figurative, then it is expected that the angle of rotation and the time required behave linearly to each other - because observations sequence is simply longer if more needs to be rotated. If the propositional theory is true, then there is no reason for such linearity. Since she is still there, we have a strong argument for Kosslyns position.

Pylyshyn not accept such arguments. He thinks that there are the time intervals from the knowledge of the subject: You need to rotate the objects only because in larger angular longer because they know that the rotation of such an object takes longer and therefore unconsciously their reactions to customize ( Pylyshyn speaks of a "tacit -knowledge explanation" ).

The state of the debate

Apparently, the debate is difficult to decide - both parties can explain the phenomena. In addition, both theories have advantages and disadvantages. So Pylyshyns explanations of experimental results often seem ad hoc, it has his theory in terms of simplicity, uniformity and economy to their strengths. So what to do? A trend in recent years is, by means of imaging techniques to look into the brain to see how because there really is worked in visual presentation.

However, these results are by no means clear: On the one hand, it was found that in pictorial ideas (especially the visual cortex), strong activities are actually present in the brain regions that are involved in the processing of visual impressions. Here seem to work some of the same mechanisms. On the other hand, neuropsychologists have found a Doppeldissoziation between visual perception and visual perception. That is, perception and visual imagination can be disturbed independently. And this means that here partly different mechanisms must be used. So the question is not empirically decided. It also raises the question of whether or not there a neurobiological decision is possible: In an imaging method we will never find Pylyshyns propositions. However this is simply that his theory is formulated on another ( the computational ) level.