Alcohol increases commission error rates for a continuous performance test

Background: Studying the effects of alcohol on Continuous Performance Test (CPT) performance was of interest for two reasons, i.e., (1) perhaps becaus e of the ease of the task used in previous experiments, alcohol has not bee n found to impair performance, and (2) CPT commission errors (described bel ow) have been related to impulsive behavior. Methods: In this study, the CPT featured both an Immediate Memory Task (IMT ) and a more difficult Delayed Memory Task (DMT). We compared the performan ce of 18 subjects under both alcohol and placebo conditions, using a within -subject design. Both the IMT (0.5-sec delay) and the DMT (3.5-sec delay, w ith distracter stimuli at 0.5-sec intervals) required the subject to respon d if a briefly displayed number was identical to the one presented before i t. Stimuli included target (identical match), catch (4 of 5 digits matched) , and novel (random number) stimuli. On 2 separate days, subjects performed between administrations of three hourly placebo drinks or three hourly dri nks containing 0.20 g/kg of alcohol (producing peak breath alcohol concentr ations of approximately 0.035%). Results: The main finding was that alcohol consumption increased responses to catch stimuli (i.e., commission errors) in the DMT. In contrast, perform ance in the IMT (the easier task)was unaffected by alcohol. Commission erro rs measured during peak breath alcohol concentrations were significantly co rrelated with scores on the Barratt Impulsivity Scale for both the IMT and DMT. Discriminability (A') between target and catch stimuli was reduced by alcohol for the DMT only. Conclusions: These data indicate that even small amounts of alcohol can pro duce measurable changes in CPT performance parameters if the task is of suf ficient difficulty and that commission errors can be increased by alcohol c onsumption.