Upon introspection, people claim to have images in their mind which
illustrate their thoughts. As loose layman vocabulary this is fine.
However, as psychologists, we cannot adhere to this idea as if I
see something and have an image in my head of it, who is looking at
the image? A 'little man'? So who sees his mental images in his
head? It can go on ad infinitum. The imagery debate is concerned
with describing what 'thing' is in our 'mind' when we think and how
it occurs in the first place. The alternatives are images as
propositions, as data structures, and a system of rules.
Pylyshyn talked about representations and claimed that they were propositions
(assertions) organised hierarchically. When a concept is active or
if concepts are closely related, they go to the top of the
hierarchy. He suggested that the representation is constructed from
an interpretation of pictures and words, not a snapshot of them.
Kosslyn suggested that images have physical characteristics. He
believes that images are produced by the same mechanisms as visual
perception, and that effective visual processing is dependent on the
imaging process. Supporting this, subjects have taken the same
amount of time to , say, imagine scanning an object as it does to
actually do so. Also, patients with hemifield neglect only have
half a mental image. Shepard also provided evidence for this by
showing how the reaction time taken to identify shapes is a function
of the degree to which it is rotated from the vertical axis.
Kosslyn was criticised because it is possible that the data aquired
by the experiments mentioned earlier could have been influenced by
the subjects actng how the researcher expected them to.
To support Kosslyn's account, he created a computer model with the
intention that it could do exactly what a human can. By doing so he
conformed to implementation - dependence, and we all know that
cognition is implementation - independent ( as is Pylyshyn's model).
Also, critics claimed that the visual buffer is primitive, and
thus cannot be affected by expectations and intentions.
The the timing of imagery may be congruent with the real thing
as an effect of previous experience (or not?).
Pylyshyn may be criticised because she claims that cognition is
computation. This has been disproved by the symbol grounding
problem. Also, the nature of the hierarchical structure of imagery
is not congruent with the PDP models which are becoming more popular
for mind modelling.
P.S. Am I supposed to konw the ANSWER to this (I suppose if there
were an answer, it wouldn't be an imagery DEBATE).
See Ya, Mel.
This archive was generated by hypermail 2b30 : Tue Feb 13 2001 - 16:23:58 GMT