Task artifacts and strategic adaptation in 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The change signal task is a variant of a two-alternative forced-choice (2AFC) task where the initial stimulus is superseded with the alternative stimulus (the change signal) at a delay on a proportion of trials.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, and we validate the model using the empirical data from participants who performed them sequentially. The results confirmed the existence of a dynamic hedging strategy in the change signal task, and provided evidence against a role for cognitive fatigue in producing the 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 was then constrained while fitting the remaining three task-specific parameters for the change signal task. This effectively reduced a degree of freedom in the model fitting process, and increased confidence in the model as it closely matched human performance in multiple tasks. 2013 Elsevier B.V. All rights reserved.