Cm. Moore et H. Egeth, PERCEPTION WITHOUT ATTENTION - EVIDENCE OF GROUPING UNDER CONDITIONS OF INATTENTION, Journal of experimental psychology. Human perception and performance, 23(2), 1997, pp. 339-352
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.