Approach and withdrawal actions modulate the startle reflex independent of affective valence and muscular effort.

The startle reflex is modulated during processing of pleasant and unpleasant affective cues. One explanation of this finding contends that approach and withdrawal motivational processes are key to explaining the effect. Undergraduates performed arm flexion and arm extension actions shown elsewhere to reliably elicit approach and withdrawal motives, respectively. Results showed that arm extension (a withdrawal action) was associated with the largest startles, followed by a neutral control action and arm flexion (an approach action). This pattern was not attributable to the subjective pleasantness or muscular effort associated with the actions. Results support motivational priming accounts of startle reflex modulation.