PARENTESE, the exaggerated, drawn-out form of speech people use to communicate with babies, apparently is universal and plays a vital role in helping infants to analyse and absorb the phonetic elements of their parents' language. An international study shows that infants are so good at analysing this speech that by the age of 20 weeks they begin to produce the three vowel sounds common to all human languages—"ee", "ah" and "uu". "Parentese has a melody to it. And inside this melody is a tutorial for the baby that contains exceptionally well-formed versions of the building blocks of language," explains Patricia Kuhl, a University of Washington neuroscientist. Kuhl recently headed a team of nine researchers from the US, Russia and Sweden, investigating how infants master the complex task of acquiring speech. The new study, published in the latest issue of Science, examined differences in how American, Russian and Swedish mothers speak to their infants and to other adults. The study shows that parentese is characterised by over-articulation that exaggerates the sounds contained in words. "In normal, everyday speech, adults generally race along at a very fast pace," Kuhl says. "But we know it is easier to understand a speaker when they stretch out sounds.