Jeremy M. Wolfe a,b, Aude Oliva a,b, Todd S. Horowitz a,b,
Serena J. Butcher c, Aline Bompas d
a Center for Ophthalmic Research, Brigham and Women's Hospital, USA
b Department of Ophthalmology, Harvard Medical School, USA
c Department of Psychology, Harvard University, USA
d Laboratoire de Psychologie Experimentale, Universite Rene Descartes, Paris,
France
Published in Vision Research 42 (2002)
ABSTRACT
In most visual search experiments in the laboratory, objects are presented on an isolated, blank background. In most real world search tasks, however, the background is continuous and can be complex. In six experiments, we examine the ability of the visual system to separate search items from a background. The results support a view in which objects are separated from backgrounds in a single, preattentive step. This is followed by a limited-capacity search process that selects objects that might be targets for further identi•cation. Identity information regarding the objects status (target or distractor) then accumulates through a limited capacity parallel process. The main e•ect of background complexity is to slow the accumulation of information in this later recognition stage. It may be that recognition is slowed because background noise causes the preattentive segmentation stage to deliver less e•ectively segmented objects to later stages. Only when backgrounds become nearly identical to the search objects does the background have the e•ect of slowing item-by-item selection.