T3D Re: acuity enhanced.....mechanism?

[Jim Crowell <crowell@xxxxxxxxxxxxxxx>]

At 4:36 AM -0700 3/20/98, Peter Abrahams wrote:
>
>Yes, first they say that it probably isn't due to contrast discrimination,
>but then speculate that "A better explanation of our results is that the
>summation that was observed in the letter-identification domain was caused
>by the summation's occuring in the contrast domain.  In other words,
>although visual acuity is a suprathreshold contrast task, our observed
>binocular enhancement can be explained most simply by threshold summations
>of high spatial frequencies  .... We assume that, at acuity threshold, the
>spatial frequencies of the components which we presume to be critical in
>the discrimination are sufficiently high to fall near their own contrast
>threshold.  Our observed acuity enhancement may then be accounted for by
>threshold contrast summation of these high-spatial-frequency components,
>which effectively increases the high-spatial-frequency cutoff of the
>contrast-sensitivity function."
>Just to make it crystal clear, they provide a graph of these effects.

I think this is basically a vaguer version of what I said.  To paraphrase,
using two eyes somehow allows you to see lower contrasts (i.e. the
signal/noise ratio is improved; where the relevant noise exists isn't
specified) at any given level of detail.  As a result, stuff at a very fine
level of detail and high contrast that was not quite visible before now
becomes visible.

-Jim C.

----------------------
Jim Crowell
Division of Biology
216-76
Caltech
Pasadena, CA
(818) 395-8337
jim@xxxxxxxxxxxxxxx



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