In dynamic task environments, decision makers are vulnerable to two types of errors: sticking too closely to the rules (excessive conformity) or straying too far from them (excessive deviation). We explore the effects of process and outcome accountability on the susceptibility to these errors. Using a multiple‐cue probability‐learning task, we show that process accountability encourages conformity errors and outcome accountability promotes deviation errors. Two additional studies explore the moderating effects of self‐focused and other‐focused group norms. Self‐focused norms reduce the effect of process accountability on excessive conformity. Other‐focused norms reduce the effect of outcome accountability on excessive deviation. Our results qualify prevailing claims about the benefits of process over outcome accountability and show that those benefits hinge on prevailing group norms, on the effectiveness of prescribed decision rules, and on the amount of irreducible uncertainty in the prediction task. Copyright © 2016 John Wiley & Sons, Ltd.