Keren-Portnoy, T. & Vihman, M.
University of York, UK
The importance for early lexical development of hearing words in isolation as compared with having to segment them from running speech is hotly debated (e.g., Brent & Suskind, 2001, Gerken & Aslin, 2005). Although several studies have shown that infants can segment words from continuous speech, this may not be the primary way that infants learn their first words. Brent and Siskind (2001) demonstrated that isolated-word frequency in input speech better predicts later word use than word frequency overall, while Junge et al. (2012) found more reliable 10-month-old learning based on isolated words than words heard in passages. We tested the comparative effects of input word use in isolation and in sentence-final position on 12-month-olds? word learning. A picture book with animals whose names were unlikely to be familiar to infants (e.g., condor, dassie, pudu) was read by parents to their infants over 3 weeks. The animal names appeared in the book either in isolation or sentence-finally. Each infant was then tested using the Head-turn Preference procedure on (i) trained words heard in isolation, (ii) trained words heard sentence-finally, and (iii) phonotactically-matched untrained words. Results show a tendency (F = 2.936, df = 1.4, p = .09) for group differences in mean looking times. When comparing each two word types in pairs, using relative percentage of looking to each type, we found greater attention to words heard in isolation than to those heard in sentences (p = .02), a tendency towards greater attention to words heard in isolation over untrained words (p = .07) and no significant difference between attention to words heard in sentences vs. untrained. We are now running a follow up experiment, which will allow more clearly interpretable pairwise comparisons. Our study provides further evidence that isolated words may afford a ?critical wedge? into the speech stream.