Accuracy, confidence, and reaction time (RT) are robustly coupled: confidence is higher, and responses are faster for correct than error trials. However, the magnitude of these relationships is typically modest in standard two-choice tasks. Here we show that the strength of these relationships depends on choice-set size, increasing substantially when decisions involve multiple alternatives. We first re-analyzed 10 large datasets from the Confidence Database, which demonstrated that the associations between accuracy, confidence, and RT are modest in two-choice lab tasks. We then performed simulations using signal detection theory and evidence accumulation models, both of which reveal that increasing the number of response alternatives strengthens the trial-by-trial associations among these variables when overall performance is equated across conditions. Critically, we observed the same pattern empirically in a large behavioral dataset (N = 200) using a noisy digit-identification task with 2-, 4-, and 8-choice conditions in which accuracy was held near the same target level. Multiple control analyses indicated that the stronger associations were not explained by distributional width, target-digit identity, stimulus-noise differences, or session-specific practice effects. Overall, our findings demonstrate that the magnitude of behavioral coupling among accuracy, confidence, and RT depends on the number of choices available and may therefore be particularly strong in real-world settings where multiple alternatives are the norm.