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, observer s searched for the presence of a square defined by subjective contours. The first experiment demonstrated that the left hemisphere made more errors fo r detecting these objects. The second experiment showed that the increased errors were due to the left hemisphere responding to the individual feature s 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 subject ive object. A third experiment was conducted to determine if performance fo r the right hemisphere was due to object level processing. It was shown tha t the right hemisphere only makes illusory conjunctions for features within perceptual groups while the left hemisphere makes illusory conjunctions bo th within and across perceptual groups, providing converging evidence for o bject level processing in the right hemisphere. The results suggest that th e right hemisphere conjoins feature information for the perception of objec ts. (C) 1998 Elsevier Science Ltd. All rights reserved.