NIDA Research Monograph series

ion (Pearl, Domino and Rennick 1973), attention (Dittrich, Battig and Von Zeppelin 1973, Casswell and Marks 1973b) and reading comprehension (Clark, Hughes and Nakashima 1970). The inference that a drug-induced memory disruption occurs in these experiments is drawn from the requirements of the cognitive tasks themselves. For instance, under the digit span task, the subject is presented with a number of digits and then is immediately asked to recall them in order. Under the serial subtraction task, the subject is given some starting number and then is asked to subtract some constant number, such as seven, until zero is reached. In other words, at any given moment in time the subject needs to remember what the current number is and to perform, from memory, previously learned arithmetic operations. Likewise, the goal directed serial alternation task requires the subject to hold a number in memory and to perform cognitive functions directed toward a remembered goal. It seems apparent that one could infer that marijuana impairs memory directly from marijuana-induced performance decrements under these cognitive tasks. The inference that memory impairment mediates marijuana-induced performance decrements on cognitive tasks is less direct in the case of cognitive tasks involving, for example, concept formation, abstraction, or reading comprehension. Nevertheless, in each of these latter cases the inference is appropriate since each involves the acquisition of some cognitive behavior, and the process of acquisition may be viewed cognitively as consisting of memory processes and retrieval processes. A possible exception to this interpretation is any cognitive task that involves the fundamental process of attention (DeLong and Levy 1973, 1974). It should be noted, however, that there are several considerations which have served to mitigate the inference, drawn from cognitive task performance, that marijuana impairs memory or that memory impairment mediates marijuana-induced impairments in cognition. The primary consideration is that subsequent research did not always empirically confirm the earlier findings of marijuanainduced performance decrements on these same cognitive tasks. For example, in selected experiments, marijuana did not affect performance on such cognitive tasks as: digit-symbol substitution (Hollister and Gillespie 1970), choice and concept formation (Peters et al. 1976), reaction time (Rossi, Kuehnle and Mendelson 1977; Kvalseth 1977), digit span (Waskow et al. 1970; Rafaelsen et al. 1973), goal directed serial alternation (Tinklenberg et al. 1972), serial subtraction (Melges et al. 1970a), time production (Jones and Stone 1970; Tinklenberg et al. 1976), card sorting (Beautrais and Marks 1976), and attention (Sulkowski, Vachon and Rich 1977, Vachon and Sulkowski 1976; Vachon, Sulkowski and Rich 1974). Comprehensive reviews of the experimental literature pertaining to marijuana’s effects on cognitive tasks of the types discussed herein are available elsewhere (see especially: Abel 1975; Braude and Szara 1976; DeLong and Levy 1974; Jones 1976; Miller 1974; 1976). A general perusal of these earlier reviews indicates that