One Model, Two Tasks: Decomposing the Change Signal Task


The change signal task is a variant of a two-alternative forced-choice (2AFC) task where the initial stimulus is superseded with the alternative stimulus (the change signal) at a delay on a proportion of trials. Taking advantage of the overlap in task requirements, we present a single model that can perform both tasks. We validate the model using the empirical data from participants who performed both tasks sequentially. The results confirmed the existence of a dynamic hedging strategy, and showed that cognitive fatigue had little, if any, role in slower response times with increased time on task. When fitting the 2AFC task, the model required adjustment to one architectural parameter while the rest were left to defaults. That parameter is then constrained while fitting the remaining three task-specific parameters of the change signal task. This effectively reduces a degree of freedom in the larger task, and increases confidence in the model as it closely matches human performance in multiple tasks.

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