Symptoms and interference from memory in schizophrenia: evaluation of Frith's model of willed action

The present study was undertaken to test Frith's [The Cognitive Neuropsychology of Schizophrenia, 1992. Erlbaum (UK) Taylor and Francis, East Sussex] model which states that certain symptoms of schizophrenia arise from diminished capacity to regulate willed (goal-directed) and stimulus-driven action systems. A total of 107 patients were administered the Rey Auditory Verbal Learning Test (RAVLT), a task that on interference trials requires individuals to recall target material while suppressing non-target distracting stimuli from memory. Symptom ratings were obtained using the SANS/SAPS [Andreasen, N.C., 1984. Scale for the Assessment of Negative Symptoms/Scale for the Assessment of Positive Symptoms [Manual] University of Iowa Press, Iowa City]. It was predicted that (1) negative symptoms would result in diminished recall, reflecting compromised activation of the willed action system, and (2) disorganized symptoms would be associated with heightened interference susceptibility resulting from diminished ability to suppress the stimulus-driven action system. Results revealed that diminished recall was related to negative, but not disorganized or positive symptoms. Symptom ratings were also evaluated in a subset of patients with intrusion error data (n=38). In this subset, it was found that patients who committed intrusion errors on the interference trials evidenced more disorganized, but not negative or positive symptoms, than individuals failing to commit such errors. These findings provide some support for Frith's hypothesis that impaired regulation of action systems may underlie some of the specific symptoms and cognitive impairments of this illness.