Disentangling human decisions under strong time pressure in an expectation-based 2AFC auditory task

Abstract

Decision-making in humans is difficult to study because it is a complex process influenced by many factors. How are these factors combined and their effect is studied in rats. Recent studies have thoroughly characterized the behavior of rats performing a Two-Alternative Forced Choice (2AFC) auditory task, in which the probability to repeat the previous stimulus category is varied in a blockwise fashion. These studies showed that rats exhibit a transition bias: a tendency to alternate/repeat the previous response using an estimate of the probability given the recent trial history. However after error trials, the transition bias was null. Even though it is suboptimal, this so-called reset strategy has been shown to be highly robust and present in many task variants. On the other hand, the reaction times of rats performing the 2AFC task has been shown to be governed by two independent processes: one that depends on the accumulation of the stimulus evidence and a second, stimulus-independent process that only depends on the time elapsed since the beginning of the trial. Here we have investigated the behavior of human subjects performing an auditory 2AFC task presenting the same type of correlations experienced by the rats. We found that their strategies were more heterogeneous, with some subjects displaying a clear reset strategy while others developed a more optimal strategy. Furthermore, the reaction times of the human subjects showed evidence of being influenced by the two processes mentioned above, suggesting that the existence of the two different mechanisms described in rats may be a general feature present across species.