Response Time as a Proxy for Decision Confidence: Insights from Type-2 ROC Analysis

This study explores the use of response time (RT) data in type-2 receiver operating characteristic (ROC) analysis, a method traditionally used to examine the relationship between confidence and response correctness. Analyses of 16 perceptual decision-making datasets revealed that: (1) RT data contains roughly two-thirds as much information about response correctness as confidence; (2) RT carries unique predictive power for response correctness, independent of confidence; (3) RT and confidence interact synergistically, with confidence becoming a stronger predictor of response correctness when RT is short; (4) Despite these unique properties of RT, type-2 sensitivity (meta-d′) derived from RT and confidence showed a reasonably high correlation across subjects. These findings carry two key implications. First, in the absence of confidence data, RT can serve as a viable proxy, incurring minimal cognitive and logistical costs. This makes type-2 analysis feasible across various settings, potentially including infant and animal studies. Second, when both RT and confidence data are available, their combined use in type-2 analysis offers complementary insights into the processes underlying subjects’ behavior. To illustrate this, we present a simulation showing how the observed behavioral patterns align with the two-stage dynamic signal detection model. We propose that RT-based type-2 analysis is a valuable tool for researchers, helping to uncover previously underexplored aspects of decision-making behavior.