Valence is a principal dimension by which we understand emotional experiences, but oftentimes events are not easily classified as strictly positive or negative. Inevitably, individuals vary in how they tend to interpret the valence of ambiguous situations. Surprised facial expressions are one example of a well-defined, ambiguous affective event that induces trait-like differences in the propensity to form a positive or negative interpretation. To investigate the nature of this affective bias, we asked participants to organize emotional facial expressions (surprised, happy, sad) into positive/negative categories while recording their hand-movement trajectories en route to each response choice. We found that positivity-negativity bias resulted in differential hand movements for modal versus nonmodal response trajectories, such that when an individual categorized a surprised face according to his or her nonmodal interpretation (e.g., a negatively biased individual selecting a positive interpretation), the hand showed an enhanced spatial attraction to the alternative, modal response option (e.g., negative) in the opposite corner of the computer screen (Experiment 1). Critically, we also demonstrate that this asymmetry between modal versus nonmodal response trajectories is mitigated when the valence interpretations are made under a cognitive load, although the frequency of modal interpretations is unaffected by the load (Experiment 2). These data inform a body of seemingly disparate findings regarding the effect of cognitive effort on affective responses, by showing within a single paradigm that varying cognitive load selectively alters the dynamic motor movements involved in indicating affective interpretations, whereas the subjective interpretations themselves remain consistent across variable cognitive loads.