Neuroscience Seminar : Signatures of time-dependent urgency during human perceptual choice
Dr Peter Murphy (University Medical Center Hamburg)
Monday, 06 June 2016, 12.30pm to 1.30pm
C113 Weiskranktz Room, Department of Experimental Psychology
Hosted by Annabelle Blangero (email@example.com)
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.