Several models (e.g., Batchelder, 2002;<cite> Brent's (1999a)</cite> MBDP-1 model; Davis, 2000; de Marcken, 1996; Olivier, 1968) simultaneously address the question of vocabulary acquisition, using previously learned word-candidates to bootstrap later segmentations. (It is beyond the scope of this paper to discuss these in detail; see Brent 1999a,b for a review.)