Researchers at the Hebrew University of Jerusalem have uncovered new insights showing that the size of an anticipated reward directly increases impulsivity, driven by specific dopamine-related brain mechanisms.
Led by Prof. Eran Lottem of the Edmond and Lily Safra Center for Brain Sciences (ELSC), the study, published in *Biological Psychiatry*, reveals that the more valuable a reward is expected to be, the harder it becomes to resist acting prematurely—even when waiting would yield better results. This challenges traditional views of impulsivity as mere poor self-control or irrationality, instead identifying it as a predictable consequence of how the brain processes value.
“Our findings show impulsive behavior emerges from a Pavlovian bias—an automatic brain response to valuable rewards—that pushes us to act before we think,” said Prof. Lottem. “It’s not just a failure of willpower but a built-in mechanism shaped by learned associations.”
To explore this, the team designed an experiment where participants had to delay responses to receive water rewards of varying sizes. Larger rewards triggered significantly more premature actions, revealing that impulsivity scales with expected reward value.