Capuchin monkeys (Sapajus [Cebus] apella) prefer larger sooner sequence payouts

The peak-end effect, in which evaluations of experiences are disproportionately influenced by their most intense, most recent, or final moments, is seen consistently in humans but inconsistently in nonhuman primates. Understanding in what species and contexts these biases appear can help us better understand the evolution of these decision-making biases. Previous evidence in monkeys is contradictory, likely due to differences in experimental procedures. Thus, to assess whether capuchin monkeys (Sapajus [Cebus] apella) exhibit such biases, we tested 14 individuals in a manual two-item food sequence task. Across conditions, monkeys consistently preferred to consume the higher value item first, showing a start bias rather than the end bias characteristic of human decision-making and seen in some other primate studies. This preference was strongest among low- and middle-ranking individuals. However, replacing the low-value item with a delay did not affect choices, suggesting that it was discounted or ignored when monkeys were making their decisions. We consider several explanations for why our monkeys show a start bias rather than an end bias, including possible methodological influences on their choices, and how this affects our understanding of the evolution of these biases. (PsycInfo Database Record (c) 2026 APA, all rights reserved).