ABSTRACT
Introduction In 1998. Heinrichs and Zakzanis published an exhaustive meta-analysis of 204 studies from the cognitive deficit literature in schizophrenia (Heinrichs & Zakzanis. 1998). The analyses provided some evidence of a selective deficit in verbal memory performance compared with other cognitive domains. but against the backdrop of a broadly based impairment in cognitive functioning. A contemporaneous meta-analysis of 70 studies by Aleman and colleagues (Aleman. Hijman. de Haan. & Kahn. 1999) also emphasized the verbal memory deficit in this illness. Notable for its absence from either review was the Digit Symbol Substitution Test (DSST) from the Wechsler Adult Intelligence Scale (Wechsler. 1997). The omission is significant because the DSST is perhaps the most widely known and used measure of information processing speed. a dimension of cognitive performance that has received growing attention in the field in recent years. and has been a focus of research in our group (Bellack. Gold. & Buchanan. 1999: Dickinson & Coursey. 2002: Dickinson. Iannone. Wilko & Gold. 2004; Gold. Goldberg. McNary. Dixon. & Lehman. 2002: Gold. McMahon. Wilk. Thaker. Bellack. & Buchanan. in preparation).
