In this paper, we validate Macaro's (2006) model of strategy use among language learners by assessing the amount of neural activity around the prefrontal cortex, the supposed locus of working memory (WM). We also examine whether WM activation during first language (L1) strategy deployment is lower than WM activation during second language (L2) strategy deployment, as predicted by Macaro's model. In the analysis, we consider data obtained through an innovative neuroimaging technique (near-infrared spectroscopy) and stimulated-recall interviews. The results reveal greater brain activity during execution of the L1 and L2 tasks than in a control condition; further, use of strategies in the L2 resulted in stronger WM activation than use of strategies in the L1. These results provide partial support for the validity of Macaro's model. (Contains 3 tables, 4 figures and 8 notes.)