ON THE LEFT AND RIGHT-HEMISPHERE VISUAL PROCESSING THAT PRECEDES RECOGNITION

Three experiments, and a replication of each, investigated the noncons cious prerecognition visual processing given left visual field (LVF) a nd right visual field (RVF) letter inputs. Each input was a vertically arrayed pair of letters in which three variables were manipulated: (1 ) the same letter twice vs one each of two letters, (2) same vs 180-d egrees difference in orientations within each letter pair, and (3) nor mal vs mirror-image letter form. The procedure presented all pairs of letter combinations in pairs of pre- and postmasked 10-msec flashes; t he subject's task was to report which flash of each pair appeared to l ast longer. When letter pairs differed on all three variables, RVF pre sentations of mirror-image letters were judged to be longer than equal presentations of normal letters; the reverse occurred for LVF present ations. When one normal and mirror-image letter were presented, RVF pr esentations of mismatched orientations were judged to be longer than m atched orientations, and the reverse was true for LVF presentations. W hen pairs of two normal letters were presented, no processing differen ce between LVF and RVF presentations was observed. A fourth experiment tested presence/absence detection of the letter pairs under the input conditions of the main experiments and showed those conditions to pro duce chance-level presence/absence detection. These results suggest th at each hemisphere can perform its own prerecognition operations and t hat neither hemisphere is necessarily specialized for any particular p rerecognition visual operation.