[photo-3d] Re: Infant stereopsis

[Jim Crowell <jcrowell@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

> What does "forced-choice" mean anyway?
> 
> Bruce (Pursuing a medical degree in my spare time) Springsteen

In a forced-choice preferential looking experiment, two displays are placed
side-by-side, one two the baby' left & one to the right.  They vary along
some dimension, & one is presumed to be more boring than the other; for
example, in an acuity experiment one would contain a pattern & the other
would be uniform gray, in a stereo experiment one would contain depth & the
other would be flat.  There are one or more observers, who can see the baby
but can't see the displays (or they videotape the babies & have the
observers look at the tape later).  In the most common variant, the observer
has to choose, based on the baby's behavior over the course of a
presentation, which side the interesting display was on.

The two other main methods for studying infant vision are (1) habituation,
in which you show a baby something for a while until he/she gets bored, then
show them something else & if they look at it you assume it looks novel,
i.e. they can tell the difference.  This method has both theoretical and
practical problems; under some conditions it appears that babies prefer to
look at familiar things rather than novel ones, and trying to get babies to
do anything when they're bored is never a good idea. (2) Visually-evoked
potentials (VEPs): you show a baby a flickering pattern & look for a
corresponding flicker in the EEG.  This is far & away the easiest method,
but as always with physiological measures of brain activity it's a bit
tricky deciding what it means about perception.

-Jim C.


-------------------------------------
Jim Crowell, Ph.D.
Dept. of Psychology
Cognitive/Experimental Group
Townshend Hall
1885 Neil Ave. Mall
Ohio State University
Columbus, OH 43210
mailto:crowell@xxxxxxxxxxxxxxxxx
mailto:crowell@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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http://vision-lab.psy.ohio-state.edu/crowell/