A small experiment found that amphetamine increased choices requiring greater effort, especially when the chance of reward was lower. That did not mean the participants became more sensitive to the size of the possible reward.
Wardle and colleagues studied 17 healthy adults across placebo, 10-mg and 20-mg d-amphetamine sessions under counterbalanced double-blind conditions. The Effort Expenditure for Rewards Task offered easier, lower-paying and harder, higher-paying options. Trials varied both reward amount and the probability of actually receiving it. The harder task also took longer, making this a mixed decision rather than a pure measure of physical effort.
The main dose comparison was clearest at 20 mg; the 10-mg-versus-placebo comparison was only a trend. Drug effects were significant at medium and low reward probabilities, but not the highest probability. The drug did not significantly change how reward magnitude influenced choices. Amphetamine also sped button pressing, yet that speed was not a significant predictor of choosing the harder task.
The sample was small and the task combined effort, probability and timing. The drug’s effects were not specific to one neurotransmitter or brain region. Choosing more effortful uncertain options is not automatically economically optimal, nor does it establish improved real-world judgment. The study supplies no prediction that a particular person will take more risks or perform better at work. Its contribution is a conditional change in willingness to tolerate costs, with the negative reward-magnitude and motor-explanation results helping narrow the claim.
See a separate experiment distinguishing effort from reward learning.