Abstract
Classic foraging theory predicts that humans and animals aim to gain maximum reward per unit time. However, in standard instrumental conditioning tasks individuals adopt an apparently suboptimal strategy: they respond slowly when the expected value is low. This reward-related bias is often explained as reduced motivation in response to low rewards. Here we present evidence this behavior is associated with a complementary increased motivation to search the environment for alternatives. We trained monkeys to search for reward-related visual targets in environments with different values. We found that the reward-related bias scaled with environment value, was consistent with persistent searching after the target was already found, and was associated with increased exploratory gaze to objects in the environment. A novel computational model of foraging suggests that this search strategy could be adaptive in naturalistic settings where both environments and the objects within them provide partial information about hidden, uncertain rewards.
Highlights
Humans and other primates on the hunt for hidden rewards must search for them persistently, by thoroughly inspecting the objects in their environment
Classic foraging theory predicts that humans and animals aim to gain maximum reward per unit time
We found that the reward-related bias scaled with environment value, was in part caused by persistent searching after the target was already found, and was associated with increased exploration of objects in the environment
Summary
Humans and other primates on the hunt for hidden rewards must search for them persistently, by thoroughly inspecting the objects in their environment. A common and seemingly straightforward paradigm is to require participants to make actions associated with different expected amounts of reward In these settings, humans and animals consistently make actions rapidly when they are associated with large reward and slowly when they are associated with less reward or no reward [1,2,3,4,5,6,7,8,9,10,11,12]. Humans and animals consistently make actions rapidly when they are associated with large reward and slowly when they are associated with less reward or no reward [1,2,3,4,5,6,7,8,9,10,11,12] They do so even when this is a seemingly suboptimal strategy that substantially reduces their reward rate. Because they must perform the instructed action in order to continue the task, performing slowly on trials when only a small reward is available prolongs the amount of time they spend in those low-value trials
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