tamasi [at] uni-potsdam.de Academic / personal website We are extremely sensitive to small changes made to words; for example, we can distinguish 'baby' from 'vaby' with ease. This shows that we know a lot about how words are built up. However, it is still unclear when and how such knowledge arises: Are children aware of word structures before they learn to speak or, rather, they learn them as their vocabulary grows? In our research, we use pupillometry to measure how sensitive young children are to changes made to words: Are they able to appreciate the difference between correctly pronounced and slightly mispronounced words (such as 'baby' and 'vaby')? This way, we can determine what children know about words and maybe even track the emergence of such knowledge.