Multiphasic Value Biases Modelling

Modelling code for Corbett, Martinez-Rodriguez, Judd, O'Connell & Kelly (2022), Multiphasic Value Biases in Fast-Paced Decisions.

Perceptual decisions are biased toward higher-value options when overall  gains can be improved. When stimuli demand immediate reactions, the  neurophysiological decision process dynamically evolves through distinct  phases of growing anticipation, detection and discrimination, but how  value biases are exerted through these phases remains unknown. Here, 17 participants performed a motion direction discrimination task under high speed pressure, in which one alternative was more valuable than the other. By  parsing motor preparation dynamics in human electrophysiology, we  uncovered a multiphasic pattern of countervailing biases operating in  speeded decisions. Anticipatory preparation of higher-value actions  began earlier, conferring a “starting point”-advantage at stimulus  onset, but the delayed preparation of lower-value actions was steeper,  conferring a value-opposed buildup rate bias. This, in turn, was  countered by a transient deflection toward the higher value action  evoked by stimulus detection. A neurally-constrained process model featuring anticipatory urgency,  biased detection, and accumulation of growing stimulus-discriminating  evidence, successfully captured both behavior and motor preparation  dynamics. Thus, an intricate interplay of distinct biasing mechanisms  serves to prioritise time-constrained perceptual decisions. 

Results of model fits and code to create modelling related tables and figures are also included. See Readme for more details.