Strategy sequential difficulty effects are the findings that when participants execute strategies, performance is worse after a difficult strategy than after an easy strategy (Uittenhove & Lemaire, 2012). Strategy sequential difficulty effects are hypothesized to result from decreased working-memory resources following difficult strategy execution. In the present study we found a correlation between individuals' working memory and strategy sequential difficulty effects in arithmetic, supporting a working-memory account of these effects. Furthermore, we varied response-stimulus intervals, and we found decreased strategy sequential difficulty effects with increasing response-stimulus intervals. Implications of these findings for further understanding of strategic variations in human cognition are discussed.