PERCEPTION WITHOUT ATTENTION - EVIDENCE OF GROUPING UNDER CONDITIONS OF INATTENTION

Many theories of visual perception assume that before attention is all ocated within a scene, visual information is parsed according to the G estalt principles of organization. This assumption has been challenged by experiments in which participants were unable to identify what Ges talt grouping patterns had occurred in the background of primary-task displays (A. Mack, B. Tang, R. Tuma, S. Kahn, & I. Rock, 1992). In the present study, participants reported which of 2 horizontal lines was longer. Dots in the background, if grouped, formed displays similar to the Ponzo illusion (Experiments 1 and 2) or the Muller-Lyer illusion (Experiment 3). Despite inaccurate reports of what the patterns were, participants' responses on the line-length discrimination task were cl early affected by the 2 illusions. These results suggest that Gestalt grouping does occur without attention but that the patterns thus forme d may not be encoded in memory without attention.