When humans behave like monkeys: Feedback delays and extensive practice increase the efficiency of speeded decisions

The study of non-human primates has been foundational in understanding the neural origins of human decision processes, yet the approach rests on the assumption that one can validly extrapolate from the animal to the human. In the context of decision making, this requires constancy across species in physiological and cognitive processes. The former cannot be experimentally validated and therefore remains assumed, and recent findings have called into question the latter: non-human primates become increasingly urgent as the time spent making a decision increases, but humans do not; from a normative perspective, monkeys are making closer-to-optimal decisions than humans. Rather than presuming species differences, here we test an alternative hypothesis: previously overlooked differences in methodological procedures from the two research traditions implicitly reinforced fundamentally different decision strategies across the two species. We show that when humans experience decision contexts matched to those experienced by non-human primates - extensive task practice, or time-based penalties - they display increasing levels of urgency as decision time grows longer, in precisely the same manner as non-human primates. Our findings indicate that previously observed differences in decision strategy between humans and non-human primates are eliminated when the decision environment is more closely matched across species, placing a constraint on the interpretation and mapping of neurophysiological results in non-human primates to humans when there are fundamental differences in the task design.