A well-documented fact is that when schizophrenics are compared with normals or when the old are compared with the young, a decrement in performance, commonly termed psychological deficit, typically results. Not as well documented is the striking similarity between schizophrenics and the elderly in their performance on laboratory tasks. The purposes of the present discussion are (a) to document the similarity between old and schizophrenic subjects in their laboratory performance, (b) to show how this similarity may provide a tool with which to reevaluate psychological-deficit theories of schizophrenia, and (c) to provide one possible unifying explanation for the similarity between schizophrenic and old subjects.For the past 40 years the primary approach taken by psychologists to study the nature of schizophrenia has been to compare the performance of schizophrenics, or various subgroups of schizophrenics, with the performance of normals on an endless variety of tasks. This psychological-deficit approach climaxed in the 1960s with reviews of the literature that attempted to relate the decrements in performance shown by schizophrenics on a variety of different, seemingly unrelated, tasks to a single underlying deficit (e.g., Lang & Buss, 1965;Payne, 1966;Venables, 1964;Yates, 1966). Theoretically, these deficit theories related the decrement in performance shown by schizophrenics to a psychological function (e.g., attention) that was believed to be related to the cause of schizophrenia. The present difficulty with the psychological-deficit approach is that schizophrenics show a deficit almost no matter what task is used. This has resulted in a plethora of explanatory hypotheses of the schizophrenic deficit, with no way of judging the validity of one deficit theory over another.Just as well documented as the decrement in performance shown by schizophrenics when compared with normals is the decrement in performance shown by the old when compared with the young. Although the psychological Requests for reprints should be sent to