First language acquisition . . . second language acquisition: 'What's Hecuba to him or he to Hecuba?'

Second language (L2) research appeals to first language acquisition research frequently and standardly. It is important, however, to take stock from time to time of the uses that second language acquisition (SLA) makes of its sister field. Whether we use first language (L1) research to generate or bolster the importance of a particular research question, to argue for a fundamental similarity or a fundamental difference between the two sorts of acquisition, or to offer guidance in the formulation of research paradigms, it is important that we do so with our critical eyes open. This article examines the possible and specific relationships between L1 acquisition and SLA, with the aim of showing that a number of assumptions warrant closer inspection. It begins by examining the expressions 'first language acquisition' and 'second language acquisition', suggesting that the syntactic and lexical parallelism between the two masks important issues internal to the fields involved. It then explores problems in distinguishing L1 from L2 acquisition from three different perspectives: individual language learner histories, the data, and the mechanisms proposed to account for the two types of acquisition. Finally, it takes a brief look at the sociology of L1 and L2 studies, and suggests that second language study has yet to assume fully its rightful place in the academy.