DO LOCALLY DEFINED FEATURE DISCONTINUITIES CAPTURE ATTENTION

Results from previous visual search studies have suggested that abrupt onsets produce involuntary shifts of attention (i.e., attentional capture), but discontinuities in simple features such as color and brightness do not (Jonides & Yantis, 1988). In the present study we tested whether feature discontinuities (i.e., ''singletons'') can produce attentional capture in a visual search task if defined ''locally'' or over a small spatial range. On each trial, a variable number of letters appeared, one of which differed from the others in color or intensity. The location of this singleton was uncorrelated with target location. Local discontinuities were created by embedding the letters in a dot texture. In Experiment 1, display size effects for singleton targets were not reduced with the addition of a background dot texture. Similar results were obtained in Experiment 2, regardless of variations in texture density. Experiment 3 confirmed that when targets are defined by a color or intensity singleton, they are detected preattentively, and that increasing texture density yields faster detection. We conclude that the spatial range over which feature discontinuities are defined may influence the guidance of spatial attention, but it has no influence on their ability to capture attention.