Monkeys (Macaca mulatta) learn two-choice discriminations under displaced reinforcement.

To explain animal learning, researchers invoke a dominant associative construct. In contrast, researchers freely acknowledge humans’ explicit-declarative learning capacity. Here, we stretched animals’ learning performance toward the explicit pole of cognition. We tested four macaques (Macaca mulatta) in new discrimination-learning paradigms. Monkeys learned a series of two-choice discrimination tasks. But immediate reinforcement was denied. Instead, reinforcement was lagged—monkeys received feedback for trial N only after seeing and responding to the N + 1-trial stimulus. Theory suggests that lagged reinforcement will eliminate a dominant form of implicit discrimination learning. Yet monkeys still learned successfully. Thus, monkeys may have alternative learning algorithms usable when reinforcement is displaced and reinforcement learning undermined. This learning may, as in humans, take a more explicit form. This and related methods that disable associative learning—fostering a possible transition to explicit cognition—could have empirical utility and theoretical significance within comparative psychology.