Proceedings of the Annual Meeting of the Cognitive Science Society

The classic drift diffusion model of the 2AFC choice processassumes that observers select evidence accumulation thresh-olds to optimize some desired level of accuracy across the ex-periment. We argue that it is more ecologically natural to as-sume that decision-makers set this threshold adaptively, usinginformation from recent trials to adjust it for upcoming ones.To test this hypothesis, we designed and conducted a pair ofrandom dot motion discrimination experiment where the co-herence parameter that controls task difficulty varies across tri-als in a predictable manner. To analyze data from these exper-iments, we also designed a hierarchical drift diffusion modelthat allows decision-makers to adapt their evidence thresholdbased on the trend of difficulty of previous trials. Our resultssuggest that observers rationally integrate cross-trial informa-tion about trial difficulty into perceptual decision-making byadjusting their internal evidence thresholds. We briefly discussthe implications of the existence of such trial-level effort infer-ence on contemporary models of the choice process.