Distinct Mechanisms Mediate Visual Detection and Identification

• DOI: 10.1016/j.cub.2007.09.012
• Publication Date: 2007-10-02T17:13:56Z
• Authors: James M. Hillis; David H. Brainard
• Keywords: Contrast Sensitivity; Male; 03 medical and health sciences; 0302 clinical medicine; Agricultural and Biological Sciences(all); Pattern Recognition, Visual; Biochemistry, Genetics and Molecular Biology(all); Optical Illusions; Space Perception; Humans; SYSNEURO

A core organizing principle for studies of the brain is that distinct neural pathways mediate distinct behavioral tasks [1, 2]. When two related tasks are mediated by a common pathway, studies of one are likely to generalize to the other. Here, we test whether performance on two laboratory tasks that model object detection and identification are mediated by common mechanisms of visual adaptation. Although both tasks rely on the luminance pattern in images, their demands on visual processing are quite different. Object detection requires discriminating image luminance differences associated with the light reflected from adjacent objects. To encode these differences reliably, neurons adapt their limited dynamic range to prevailing viewing conditions [3-6]. Object identification, on the other hand, demands a fixed response to light reflected from an object independent of illumination [7]. We compared performance in discrimination and identification tasks for simulated surfaces. In striking contrast to studies with less structured contexts, we found clear evidence that distinct processes mediate judgments in the two tasks. These results challenge models that account for perceived lightness entirely through the action of image-encoding mechanisms.