Fast and careless or careful and slow? Apparent holistic processing in mental rotation is explained by speed-accuracy trade-offs.

A major debate in the mental-rotation literature concerns the question of whether objects are represented holistically during rotation. Effects of object complexity on rotational speed are considered strong evidence against such holistic representations. In Experiment 1, such an effect of object complexity was markedly present. A closer look on individual performance patterns, however, revealed that only some participants showed this effect. For others, rotational speed was independent of object complexity. The assumption that these fast-rotating participants use a holistic representation that equally well holds simple and complex objects would explain these results. Taking error rates into account disproved this explanation: Fast participants simply committed more errors in those conditions for which careful participants invested more rotation time. Whether this speed-accuracy trade-off is a stable personality trait or a somewhat flexible strategic choice was examined in Experiments 2 and 3. In Experiment 2, participants received monetary incentives that encouraged them to minimize errors. In line with a certain degree of flexible strategic control over speed-accuracy trade-offs, a large majority of participants showed effects of object complexity on rotational speed. When, in contrast, time pressure was induced in Experiment 3, error rates increased considerably and most participants' rotational speed became independent of object complexity. Our results indicate that all our participants performed mental rotation on a nonholistic representation and that apparent holistic processing strategies in mental rotation (and potentially also in other spatial tasks) might actually be speed-accuracy trade-offs in disguise.