Probabilistic reward- and punishment-based learning in opioid addiction: Experimental and computational data

•Opioid-addicted individuals, and controls, performed a reward- and punishment-learning task.•Computational (reinforcement learning) models were applied to describe individuals’ performance.•Behavioral results shows opioid-addicted individuals performed as well as controls on the task.•Computational modeling suggested subtle differences in how the two groups made decisions.•Specifically, the addicted group was more likely to “chase” reward when expectancies were violated.•A bias to pursue short-term reward, rather than long-term gain, may contribute to opioid addiction.

Addiction is the continuation of a habit in spite of negative consequences. A vast literature gives evidence that this poor decision-making behavior in individuals addicted to drugs also generalizes to laboratory decision making tasks, suggesting that the impairment in decision-making is not limited to decisions about taking drugs. In the current experiment, opioid-addicted individuals and matched controls with no history of illicit drug use were administered a probabilistic classification task that embeds both reward-based and punishment-based learning trials, and a computational model of decision making was applied to understand the mechanisms describing individuals’ performance on the task. Although behavioral results showed that opioid-addicted individuals performed as well as controls on both reward- and punishment-based learning, the modeling results suggested subtle differences in how decisions were made between the two groups. Specifically, the opioid-addicted group showed decreased tendency to repeat prior responses, meaning that they were more likely to “chase reward” when expectancies were violated, whereas controls were more likely to stick with a previously-successful response rule, despite occasional expectancy violations. This tendency to chase short-term reward, potentially at the expense of developing rules that maximize reward over the long term, may be a contributing factor to opioid addiction. Further work is indicated to better understand whether this tendency arises as a result of brain changes in the wake of continued opioid use/abuse, or might be a pre-existing factor that may contribute to risk for addiction.