Hemispheric specialization in the detection of subjective objects

Three experiments were conducted to examine hemispheric specialization for the detection of subjective objects. In the first two experiments, observers searched for the presence of a square defined by subjective contours. The first experiment demonstrated that the left hemisphere made more errors for detecting these objects. The second experiment showed that the increased errors were due to the left hemisphere responding to the individual features of the objects and not the objects as a whole. In the second experiment, the right hemisphere was also faster for detecting the absence of a subjective object. A third experiment was conducted to determine if performance for the right hemisphere was due to object level processing. It was shown that the right hemisphere only makes illusory conjunctions for features within perceptual groups while the left hemisphere makes illusory conjunctions both within and across perceptual groups, providing converging evidence for object level processing in the right hemisphere. The results suggest that the right hemisphere conjoins feature information for the perception of objects. (C) 1998 Elsevier Science Ltd. All rights reserved.