Preprint

[Subutai Ahmad]

The following paper (to appear in this Cognitive Science proceedings)
is available from the neuroprose archives as ahmad.cogsci91.ps.Z
(ftp instructions below).


	  Efficient Visual Search: A Connectionist Solution

				by

		  Subutai Ahmad & Stephen Omohundro
	       International Computer Science Institute

			       Abstract

Searching for objects in scenes is a natural task for people and has
been extensively studied by psychologists. In this paper we examine
this task from a connectionist perspective. Computational complexity
arguments suggest that parallel feed-forward networks cannot perform
this task efficiently. One difficulty is that, in order to distinguish
the target from distractors, a combination of features must be
associated with a single object. Often called the binding problem,
this requirement presents a serious hurdle for connectionist models of
visual processing when multiple objects are present.  Psychophysical
experiments suggest that people use covert visual attention to get
around this problem. In this paper we describe a psychologically
plausible system which uses a focus of attention mechanism to locate
target objects. A strategy that combines top-down and bottom-up
information is used to minimize search time. The behavior of the
resulting system matches the reaction time behavior of people in
several interesting tasks.


A postscript version of the paper can be obtained by ftp from
cheops.cis.ohio-state.edu. The file is ahmad.cogsci91.ps.Z in the
pub/neuroprose directory. You can either use the Getps script or
follow these steps:

unix:2> ftp cheops.cis.ohio-state.edu
Connected to cheops.cis.ohio-state.edu.
Name (cheops.cis.ohio-state.edu:): anonymous
331 Guest login ok, send ident as password.
Password: neuron
230 Guest login ok, access restrictions apply.
ftp> cd pub/neuroprose
ftp> binary
ftp> get ahmad.cogsci91.ps.Z
ftp> quit
unix:4> uncompress ahmad.cogsci91.ps.Z 
unix:5> lpr ahmad.cogsci91.ps


--Subutai
ahmad at icsi.berkeley.edu