Sean, a grad student in linguistics at University of Edinburgh who blogs at The Adventures of Auck (which has a nifty header that you get to play with), has a nice post where he walks through competing hypotheses and experiments regarding the role of pragmatic cues in children's word learning. Read it HERE. Money quote:
Children try to integrate cues from different domains into one coherent communicative intention. It is suggested that it may be harder to modify lexical entries for familiar words without a clear reason than to link novel words to familiar objects.