Imagine you are learning a new category, for example, recognising an animal you have never seen before. If someone tells you the name of this new animal as you learn to recognise it, does it make any difference? In the past decades, this question has been a matter of empirical research both on adults and infants. In particular, there is a substantial body of empirical research conducted with infants in their first years of life as well as several theories proposed to explain this phenomenon. The book reviews these studies and discusses their relevance for the debates about Linguistic Relativity and their theoretical implications.