The generalized cognitive deficit problem refers to a situation in which a generalized deficit gives the false appearance of a specific deficit due to the psychometric properties of tests, and it is an important methodological consideration in schizophrenia research. However, it also generates considerable confusion and is often used indiscriminately as a scientific criticism, even in situations to which it does not apply. Further, the generalized deficit problem creates few concerns in interpretation for many central questions in contemporary schizophrenia research. The research literature has shifted away from the traditional goal of identifying generalized vs differential deficits, and the field now demonstrates (1) increased recognition that a generalized deficit, broadly defined, probably does not exist in schizophrenia, (2) increased emphasis on explaining both shared and unique variance across measures to understand the mechanisms through which cognition relates to external variables (eg, functional outcome), and (3) increased use of neuroscientific methods to explore cognition in schizophrenia in which the structure and richness of data can be used to minimize misinterpretation of the sort that can occur when using only behavioral measures. Clearly, consideration of the generalized deficit still remains essential in certain experimental contexts, but criticisms based on this concern are unwarranted in many other situations in schizophrenia research. This commentary is intended to help clarify the distinctions between these 2 situations so that concerns will be expressed in a more selective, less reflexive, manner.
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