ILLUSORY CONTOURS AND SPATIAL NEGLECT

IT has been controversial whether the perception of illusory contours arise from higher level cognitive mechanisms that require attention or from early preattentive visual processes. We studied three patients w ith left spatial neglect who were unable to detect the left inducers o f Kanizsa illusory figures in a same/different judgment task but nonet heless showed implicit perception of the figures in a midpoint judgmen t, in that they made identical bisection for figures with illusory or real contours but very different bisection for other spatially discont inuous figures that did not yield illusory filling-in. Grouping and fi lling-in mechanisms can thus occur without explicit detection of, or a ttention to, the inducing features, consistently with the hypothesis t hat they involve preattentive visual processes. NeuroReport 9: 2481-24 84 (C) 1998 Rapid Science Ltd.