Speed-Accuracy Trade-Offs and Adaptation Deficits in Aphasia: Finding the "Sweet Spot" Between Overly Cautious and Incautious Responding.

Purpose After stroke, how well do people with aphasia (PWA) adapt to the altered functioning of their language system? When completing a language-dependent task, how well do PWA balance speed and accuracy when the goal is to respond both as quickly and accurately as possible? The current work investigates adaptation theory ( Kolk & Heeschen, 1990 ) in the context of speed-accuracy trade-offs in a lexical decision task. PWA were predicted to set less beneficial speed-accuracy trade-offs than matched controls, and at least some PWA were predicted to present with adaptation deficits, with impaired accuracy or response times attributable to speed-accuracy trade-offs. Method The study used the diffusion model ( Ratcliff, 1978 ), a computational model of response time for simple 2-choice tasks. Parameters of the model can be used to distinguish basic processing efficiency from the overall level of caution in setting response thresholds and were used here to characterize speed-accuracy trade-offs in 20 PWA and matched controls during a lexical decision task. Results Models showed that PWA and matched control groups did not differ overall in how they set response thresholds for speed-accuracy trade-offs. However, case series analyses showed that 40% of the PWA group displayed the predicted adaptation deficits, with impaired accuracy or response time performance directly attributable to overly cautious or overly incautious response thresholds. Conclusions Maladaptive speed-accuracy trade-offs appear to be present in some PWA during lexical decision, leading to adaptation deficits in performance. These adaptation deficits are potentially treatable, and clinical implications and next steps for translational research are discussed.