title: Choice certainty is informed by both evidence and decision time.
abstract: "Degree of certainty" refers to the subjective belief, prior to feedback, that a decision is correct. A reliable estimate of certainty is essential for prediction, learning from mistakes, and planning subsequent actions when outcomes are not immediate. It is generally thought that certainty is informed by a neural representation of evidence at the time of a decision. Here we show that certainty is also informed by the time taken to form the decision. Human subjects reported simultaneously their choice and confidence about the direction of a noisy display of moving dots. Certainty was inversely correlated with reaction times and directly correlated with motion strength. Moreover, these correlations were preserved even for error responses, a finding that contradicts existing explanations of certainty based on signal detection theory. We also contrived a stimulus manipulation that led to longer decision times without affecting choice accuracy, thus demonstrating that deliberation time itself informs the estimate of certainty. We suggest that elapsed decision time informs certainty because it serves as a proxy for task difficulty.
authors.affiliation: Center for Neural Science, New York University, New York, NY 10003. Electronic address: roozbeh@nyu.edu.
authors.forename: Roozbeh
authors.initials: R
authors.lastname: Kiani
authors.affiliation: Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Leah
authors.initials: L
authors.lastname: Corthell
authors.affiliation: Department of Neuroscience, Zuckerman Mind Brain Behavior Institute, Kavli Institute of Brain Science, Howard Hughes Medical Institute, Columbia University, New York, NY 10032.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Shadlen
mesh_terms: D002755:Choice Behavior / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D009039:Motion Perception / Q000502:physiology; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology*; D035501:Uncertainty; D055815:Young Adult