We present a model of early lexical acquisition. Successful word learning builds on pre-existing, self-organising categorisation capacities and through joint attentional events between the infant and the caregiver. Our model successfully accounts for the emergence of a lexical constraint, taxonomic responding, as well as a steep increase in the rate of acquisition of words, without any need for a new mechanism or rule. We discuss the role played by synapto-genesis in early infancy and pruning at the end of childhood in relation to word learning.