Visual Mechanisms

From: Taylor, Karl (
Date: Mon Mar 10 1997 - 16:45:53 GMT

I guess the short form of this is: although something is taken to be
modular (e.g. vision) is it still assumed to use the same mechanisms
that were proposed generally (i.e. computation, analog -> the hybrid

I think I understand the two different approaches to cognition that
were described earlier in the course: the computationist (symbol
manipulation) vs. the imagist (image manipulation).

Whilst reading chapter 4 of Green et al. it seemed like the same ideas
were coming up again with new names and without any mention of the
old. Are these really the same things or do they just look the same?

There is a section under Object Permanence called something like
"Invariants and Transformations" which introduces the idea of
prototypes (or templates) as a visual mechanism, and how these might be
matched to seen objects through some processes of transformation.

At the beginning of the course there was a description of an experiment
investigating recognition of 2-D projections of 3-D objects. The
suggestion was that the time taken to recognise an object was
proportional to how much one image was rotated from another. This was
evidence for the validity of the mental images theory.

Are these two ideas must be the same? Doesn't the imagist concept of
cognition involve this same use of templates and tranformation
described for vision?

The chapter also introduced the idea of coded descriptions (i.e.
verbal, parametric). These sound like they use symbols. So aren't these
like algorithms?

So here I am. I don't understand if these things are meant to be the
same or if this is just some similarity.

I thought, if invariants vs. tranformations is the same as symbols vs.
images then wouldn't a "solution" be the hybrid approach, like before?
i.e. that we use descriptions in reference to some descriptions
ultimately ground in images.

p117 of Green says:
"...the representation can be envisaged as a generalisation of the
"form" [the same as a mental image?] plus parameter means of encoding
global shape [the description, right? A string of
symbols?]...recognition does not involve extracting the invarient
information over exemplars but extracting the parameters of the form

Is this the same as I imagined the hybrid theory would be?

It would make sense to me to suggest that something that is modular
might still uses symbols and images, but I am not sure if I am supposed
to assume this to be true, and these things mentionad above are the
same, or not.

Please help.

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