Topic: juice reward sizes

Value optimization is a defining principle of economic behavior. To uncover the underlying psychological and neural processes, we developed a behavioral task based on the ‘knapsack problem’. Given several items, each with a value and weight, the objective is to maximize value within the weight limit of the knapsack. Two rhesus monkeys solved a touchscreen-based version that equates weights with juice reward sizes. The animals performed well above chance and achieved at least 75% of the optimal reward value on 80% of all knapsack trials. We defined each unique set of items as an ‘instance,’ and