Performance measures, including standardized test scores or cognitive tasks, are commonly conceptualized as stable measures, yet are often unreliable indices of skill. We examine two contextual factors, performance pressure and feedback, that may influence the extent to which individuals demonstrate their cognitive capacity by manipulating uncertainty and thereby changing the nature of participants' cognitive task engagement. We manipulate pressure prior to adults completing two cognitive tasks: a working memory (WM) and verbal reasoning task with some (Study 1) or no performance feedback (Study 2). Pressure increased demonstrated WM capacity, which could be explained by increased task-directed effort. The incentivizing effects were greater when feedback was provided. Those under pressure maintained their motivation to perform, which predicted performance gains, despite being more stressed and anxious than controls. Combined, this suggests that often relied upon cognitive performance indices may be malleable to contextual features and might not reflect true capacity or potential. [This paper was published in "Journal of Applied Research in Memory and Cognition" 2022.]