Abstract
Many difficult decisions are made by accumulating ambiguous evidence over time. The brain’s arousal systems are rapidly activated during such decisions. How do these rapid (“phasic”) boosts in arousal affect the decision process? Here, we have unveiled a general principle of the function of phasic arousal: suppressing suboptimal biases in evidence accumulation. We quantified phasic arousal as rapid dilations of the pupil. Pupil dilations predicted reduced biases in a range of decision-making tasks and different species. In a challenging sound-detection task, both mice and humans were less biased under high arousal. Similar bias suppression occurred when optimal biases were neutral, conservative or liberal, when evidence was accumulated from memory, and for risk-seeking biases in decisions entailing the accumulation of numerical values. In all cases, the smaller behavioral biases were explained by specific changes in evidence accumulation. Thus, phasic arousal calibrates a key computation during decision-making.
Footnotes
↵* shared senior
↵# lead contact
We rewrote the manuscript to consistently interpret the pupil response in terms of phasic arousal. We also conducted one new experiment in which we systematically manipulated signal probability, and found that, within the same subjects, phasic arousal flexibly reduces both conservative and liberal accumulation biases in a context-dependent manner. Finally, we replicated the pupil-predicted suppression of biases of both signs in a large sample of human subjects performing a memory task; bringing in yet another mode of decision-making (memory-based decisions) further generalized our claim.
