Reactive individuals explore and make decisions more slowly than proactive individuals, paying more attention to external cues. Reactive personality types are therefore predicted to make fewer mistakes in cognitive tasks, especially in tests of inhibitory control and reversal learning that require individuals to adjust behavioral routines. However, empirical evidence for this is mixed, and work relating cognition to a broader set of phenotypic traits has been called for. Here, using the common waxbill (Estrilda astrild), we relate performance in a cognitive assay, the detour-reaching task, to differences in personality, while controlling for putative confounding factors (including sex, breath rate, body size, and mass). Contrary to theoretical predictions, we found that proactive individuals, rather than reactive, made fewer mistakes in the detour-reaching task. We used body size and mass as proxies for condition, but neither predicted personality type or cognitive performance, thus providing no support for the hypothesis that condition dependence mediates the association between proactive personality and detour-reaching performance. This work adds to a growing number of studies contributing conflicting findings on how animal personality relates to cognitive performance, which, together, appear to require novel theory and more nuanced predictions. Theory predicts that reactive personality types (i.e., slower-acting and more attentive individuals) should perform better on cognitive tasks that involve inhibiting a response to an irrelevant stimulus to reach food (inhibitory control). Tests of this hypothesis have generated contradictory results and studies that account for confounding factors are needed. We quantified performance in an inhibitory control assay among common waxbills (Estrilda astrild), while controlling for the largest set of confounding factors to date. Contrary to predictions, waxbills with a reactive personality made more mistakes in the cognitive assay. These and other recent findings suggest that a more nuanced theory on the relation between cognition and personality is necessary.