Decision biases and persistent illicit drug use: an experimental study of distributed choice and addiction

This experiment tested the hypothesis that differences in drug use are correlated with differences in decision making. The subjects were 22 drug clinic patients who had used either opiates or stimulants for an average of 10 years, and 21 community residents who reported that they had rarely used illicit addictive drugs. The procedure consisted of a series of binary choices with two consequences; they earned money and determined the intervals that separated choice trials. Each choice earned the same amount of money, but one initiated a shorter delay to the next trial, whereas the other initiated a shorter delay as averaged over the next two trials. Shorter delays were advantageous in that they increased the overall rate of earnings and they reduced the time spent waiting for the next trial. Thus, one choice was better from the perspective of the current trial, while the other choice was better from the perspective of two or more consecutive trials. Drug-clinic patients were more likely to favor the one-trial solution compared with control subjects, who were more likely to favor the two-trial solution. There were five different choice games, with different versions varying in the magnitude of the advantage for switching from the two-trial to the one-trial solution. Drug clinic and control subjects differed most in the games in which the immediate advantage of the one-trial solution was larger, and all subjects were more likely to choose the global solution when the incentive for switching to the one-trial solution was lower. The results support the view that individual differences in decision making influence the course of illicit drug use.