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ABSTRACT: Psychomotor slowing is an intrinsic feature of schizophrenia that is poorly delineated from generally reduced processing speed. Although the Symbol Digit Substitution Test (SDST) is widely used to assess psychomotor speed, the task also taps several higher-order cognitive processes. Recording motor performance on copying tasks using a digitising tablet allows a more precise measurement of psychomotor speed.
A group of 75 schizophrenic inpatients were compared to 26 healthy controls in their performance on the SDST and two copying tasks.
Factor analyses showed that the copying tasks were found to capture both a cognitively loaded factor and the motor component of psychomotor slowing better, which latter aspect is not properly assessed by the SDST.
In schizophrenia psychomotor slowing seems to exist alongside reduced processing speed.
Cognitive Neuropsychiatry 12/2008; 13(6):457-71. DOI:10.1080/13546800802439312 · 1.91 Impact Factor