In their keynote paper exploring links between early experience, phonological working memory, and language outcomes, Pierce, Genessee, Delcenserie, and Morgan (2017) propose, what this study asserts, a two-pronged hypothesis. In brief, the thesis is that the timing of language exposure and the quality and quantity of language input during an early sensitive period of phonological evolution shape the quality of phonological representations later employed by the phonological working memory system to support short- and long-term language learning. The hypothesis is two-pronged because it depends on (a) qualitative differences in the evolution of phonological representations, ending in (b) variations in the efficiency of working memory as the key constraint on language learning. This commentary explores support for these two prongs in detail.