visual cue combination articles

[Robbie Jacobs]

The following two articles are published in the journal
Vision Research, but may be of interest to readers of
this list:

(1) Jacobs, R.A. (1999) Optimal integration of texture and
    motion cues to depth.  Vision Research, 39, 3621-3629.

(2) Jacobs, R.A. and Fine, I. (1999) Experience-dependent
    integration of texture and motion cues to depth.
    Vision Research, 39, 4062-4075.

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(1) Jacobs, R.A. (1999) Optimal integration of texture and
    motion cues to depth.  Vision Research, 39, 3621-3629.

We report the results of a depth-matching experiment in which
subjects were asked to adjust the height of an ellipse until it
matched the depth of a simulated cylinder defined by texture and
motion cues.  On one-third of the trials the shape of the cylinder
was primarily given by motion information, on one-third of the
trials it was given by texture information, and on the remaining
trials it was given by both sources of information.  Two optimal
cue combination models are described where optimality is defined
in terms of Bayesian statistics.  The parameter values of the
models are set based on subjects' responses on trials when either
the motion cue or the texture cue was informative.  These models
provide predictions of subjects' responses on trials when both
cues were informative.  The results indicate that one of the optimal
models provides a good fit to the subjects' data, and the second
model provides an exceptional fit.  Because the predictions of the
optimal models closely match the experimental data, we conclude that
observers' cue combination strategies are indeed optimal, at least
under the conditions studied here.

Available on the web at:
www.bcs.rochester.edu/bcs/people/faculty/robbie/jacobs.vr99.ps.Z

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(2) Jacobs, R.A. and Fine, I. (1999) Experience-dependent
    integration of texture and motion cues to depth.
    Vision Research, 39, 4062-4075.

Previous investigators have shown that observers' visual cue
combination strategies are remarkably flexible in the sense that
these strategies adapt on the basis of the estimated reliabilities
of the visual cues.  However, these researchers have not addressed
how observers acquire these estimated reliabilities.  This article
studies observers' abilities to learn cue combination strategies.
Subjects made depth judgments about simulated cylinders whose shapes
were indicated by motion and texture cues.  Because the two cues
could indicate different shapes, it was possible to design tasks
in which one cue provided useful information for making depth
judgments, whereas the other cue was irrelevant.  The results of
Experiment One suggest that observers' cue combination strategies
are adaptable as a function of training; subjects adjusted their
cue combination rules to use a cue more heavily when the cue was
informative on a task versus when the cue was irrelevant.  Experiment
Two demonstrated that experience-dependent adaptation of cue
combination rules is context-sensitive.  On trials with presentations
of short cylinders, one cue was informative, whereas on trials with
presentations of tall cylinders, the other cue was informative.  The
results suggest that observers can learn multiple cue combination
rules, and can learn to apply each rule in the appropriate context.
Experiment Three demonstrated a possible limitation on the
context-sensitivity of adaptation of cue combination rules.  One
cue was informative on trials with presentations of cylinders at a
left oblique orientation, whereas the other cue was informative on
trials with presentations of cylinders at a right oblique orientation.
The results indicate that observers did not learn to use different
cue combination rules in different contexts under these circumstances.
These results are consistent with the hypothesis that observers'
visual systems are biased to learn to perceive in the same way views
of bilaterally symmetric objects that differ solely by a symmetry
transformation.  Taken in conjunction with the results of Experiment
Two, this means that the visual learning mechanism underlying cue
combination adaptation is biased such that some sets of statistics
are more easily learned than others.

Available on the web at:
www.bcs.rochester.edu/bcs/people/faculty/robbie/jacobsfine.vr99.ps.Z