Leaving money on the table: As diagnostic aids become more useful, operators use them less efficiently

Diagnostic aids can assist human operators in everyday and high-stakes decision tasks, but performance typically falls short of best possible levels, reflecting a tendency toward disuse. To mitigate disuse, it is important to understand how task context influences aid dependence. The present study tested the prediction that aid use will become less efficient either as the aid becomes more reliable or the decision maker's task becomes more difficult. Participants (N = 127; data collected in 2023) performed a signal detection task with and without support from a diagnostic aid, where task difficulty and aid reliability varied between subjects. Analyses compared observed levels of aided performance with the predictions of an optimal strategy. Aided performance was consistently suboptimal but fell furthest from optimal when the aid was most reliable and when the task was most difficult. Costs of disuse to decision accuracy were substantial. Findings replicate and extend earlier patterns of suboptimal use, indicating that a mechanism of disuse is a failure to increase aid dependence appropriately in response to increases in aid quality or task demand. (PsycInfo Database Record (c) 2026 APA, all rights reserved).