T3D acuity enhanced.....mechanism?

[Peter Abrahams <telscope@xxxxxxxxxx>]

>So what's the mechanism of enhancement?  Was there any
>speculation? 

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.  

>especially for a letter acuity test (which is not by any means the simplest
>measure of acuity)...

They elaborate their reasons for using a complex stimulation.  "Previous
studies have found the magnitude of binocular summation to be inversely
related to both types of complexity.....we used a complex acuity task, but
we found that the summation effects observed are explicable by the same
mechanisms previously found to underlie summation with simple detection,
without recourse to task complexity.....(another study found that)
summation levels were highest (56%) for a simple detection task as compared
with 0% for a complex pattern-recognition task"

This study is 5 years old now.  No e-mail addresses are given.  Cagenello
and Arditi are at the Vision Research Lab, The Lighthouse, NY; Halpern is
in the dept. psychology, Brandeis.
_______________________________________
Peter Abrahams   telscope@xxxxxxxxxx
the history of the telescope, the microscope,
    and the prism binocular


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