Dose-response effects of d-amphetamine on effort-based decision-making and reinforcement learning.
Level 2 - randomized trial
Individual randomized within-subject trial in humans
PubMed 32722661 · doi:10.1038/s41386-020-0779-8
What was done
Thirty healthy volunteers completed a within-subject trial testing placebo, 10 mg d-amphetamine, and 20 mg d-amphetamine. Participants performed the Effort Expenditure for Reward Task (EEfRT) to assess effort-based decision-making and the Probabilistic Reward Task (PRT) to assess reinforcement learning. Computational modeling analyzed effort discounting, probability discounting, and decision consistency. Baseline working memory and baseline effort were evaluated as potential moderators.
What was found
The abstract reports no numerical values, test statistics, or effect sizes. d-Amphetamine increased willingness to exert effort, primarily at low to intermediate expected values of reward. Computational modeling linked this to decreased effort discounting rather than probability discounting or decision consistency. The increase in effort was greater in participants with lower baseline working memory and lower baseline effort. d-Amphetamine had no significant effect on reward learning.
Why it matters
These findings demonstrate that dopamine agonism via d-amphetamine can selectively enhance effort-based motivation without altering reinforcement learning in the same individuals. This informs understanding of distinct dopaminergic mechanisms underlying motivational and learning deficits in neuropsychiatric disorders.
Limits
The sample was small (n = 30) and restricted to healthy volunteers rather than clinical populations. The abstract provides no quantitative data or precision estimates. Acute laboratory administration does not capture chronic treatment dynamics.
Cited by
- supports Dopamine is essential in both human and animal brains for effort-reward decision-making and for reinforcement learning from prior actions.