Re-examining handedness in schizophrenia: now you see it--now you don't

The present study was designed to examine patterns of handedness across tasks (i.e., those requiring less vs. greater skill) and over time (initially and 1 month later) in 72 schizophrenic patients and 105 normal controls. Two important methodologic advances were introduced: (1) two handedness tasks, varying in skill level (simple vs. complex); and (2) the addition of a retest on both tasks, 1 month later. Results show a higher incidence (43%) of mixed handedness in the schizophrenic sample than in normal controls (14.3%) on tasks requiring less precision in performance. Similar results were obtained when schizophrenic patients were retested 1 month later, RI = .88. When the more demanding set of tasks was presented, the frequency of mixed handed schizophrenics dropped by 50% at initial testing. Despite these findings, there was no evidence for stability of change over time. For example, each of the most extreme shifters at Time 1 was fully lateralized 1 month later.