The currently prevailing explanation for stereotype threat (ST) debilitation effects argues for working memory interference as the proximal mediator. Using mental arithmetic problems as the test bed, Beilock et al. (2007) have spelled out in greater detail exactly how this process might work. They propose that worries resulting from activation of the negative stereotype occupy the phonological loop, taking up capacity that could be used to remember the intermediate values produced when solving horizontal mental subtraction problems. In the current work, we test an alternative, motivational account for this effect, mere effort. The mere effort account argues that ST motivates stigmatized participants to want to perform well, potentiating the prepotent response on the given task. In Experiment 1 we identified a possible prepotent response for horizontal subtraction, termed the method of adjustment (e.g., adjust the second number to the nearest 10, subtract the two numbers, and then add the adjustment). Consistent with the mere effort account, Experiment 2 showed that ST potentiated the prepotent approach, the method of adjustment. Experiment 3 pitted the mere effort account against the working memory account. Working memory predicts debilitation effects on horizontal subtraction problems when participants need to use the phonological loop (i.e., entering answers from left-to-right), whereas mere effort predicts that the potentiated use of the method of adjustment should facilitate performance when answers must be entered from left-to-right. Results supported the mere effort account. Finally, Experiment 4 showed that when we control for the effect of the potentiated prepotent response, instead of performing more poorly, threatened participants perform better than no threat participants. Overall, these experiments support the mere effort account, which argues for motivation as a core process in producing ST effects.