Neuroscience Seminar : Signatures of time-dependent urgency during human perceptual choice

Abstract: Decision-makers must often balance the desire to accumulate information with the costs of protracted deliberation. Optimal, reward-maximizing decision-making can require dynamic adjustment of this speed/accuracy trade-off over the course of a single decision. However, the extent to which human decision-makers might flexibly deploy such a time-dependent decision policy has been the subject of much recent debate. In this talk, I will present a series of studies identifying several signatures of time-dependency in human perceptual decision-making, along with their possible neural source. Targeted behavioural analyses and quantitative model comparisons revealed that human observers responded to deadline-induced speed pressure by lowering their criterion on accumulated perceptual evidence as the deadline approached – as was required to maximise performance-related rewards in this context. In the brain, this time-dependent effect was reflected in dynamic urgency that pushed decision-related motor preparation signals closer to a fixed threshold. Moreover, additional analyses and biophysically-oriented modelling indicated that global modulation of neural gain, as reflected in specific, decision-related fluctuations in pupil diameter, is a plausible mechanism for the generation of this urgency. Collectively, these findings highlight the flexibility of human decision-making under speed pressure and build on recent reports from the non-human primate literature arguing that context-sensitive time-dependency is a critical feature of the decision process.