To examine hemispheric differences in the mode of information processing, 24 normal right-handed subjects were required to make same or different responses to a set of letters varying in number from two to four which were all identical or contained one letter differing from the rest. When letters were presented in the normal upright position, the left hemisphere showed serial processing wherein reaction times increased as a function of number of letters. The right hemisphere, however, showed no increase of reaction times, i.e. parallel processing. When letters were presented in the inverted upside-down position, the left hemisphere showed partial serial processing, despite letters being analyzed physically. The results suggest that visuopatial analysis doesn't always force parallel processing in the left hemisphere.