How Does Lexical Acquisition Begin? A cognitive perspective

Lexical acquisition is a critical stage of language development, during which human infants learn a set of word forms and their association with meanings, starting from little a priori knowledge about words they do not even know whether there are words in their mother tongues. How do the infants infer individual words from the continuous speech stream to which they are exposed? This paper intends to conduct a comprehensive review of contemporary studies on how the lexical acquisition starts. It first gives a brief introduction to language development, and then examines the characteristics of the speech input to lexical-learning infants and the speech perceptual abilities they have developed at the very beginning of the learning. Possible strategies of speech segmentation for word discovery and various cues that may facilitate the bootstrapping process involved in the learning, including the prosodic, allophonic, phonotactic and distributional cues, are discussed in detail, and a number of questions concerning the cue-based studies are asked: how do the infants acquire the cues for discovering words? Are the cues the starting point, or the by-product, of the learning? Is there any more fundamental cognitive mechanism that the infants exploit to induce the cues and words?