Listening to sung words rather than spoken words can facilitate word learning and memory in adults and school-aged children. To explore the development of this effect in young children, this study examined word learning (assessed as forming word-object associations) in 1- to 2-year olds and 3- to 4-year olds, and word long-term memory (LTM) in 4- to 5-year olds several days after the initial learning. In an intermodal preferential looking paradigm, children were taught a pair of words utilising adult-directed speech (ADS) and a pair of sung words. Word learning performance was better with sung words than with ADS words in 1- to 2-year olds (Experiments 1a and 1b), 3- to 4-year olds (Experiment 1a), and 4- to 5-year olds (Experiment 2b), revealing a benefit of song in word learning in all age ranges recruited. We also examined whether children successfully learned the words by comparing their performance against chance. The 1- to 2-year olds only learned sung words, but the 3- to 4-year olds learned both sung and ADS words, suggesting that the reliance on music features in word learning observed at ages 1-2 decreased with age. Furthermore, song facilitated the word mapping-recognition processes. Results on children's LTM performance showed that the 4- to 5-year olds' LTM performance did not differ between sung and ADS words. However, the 4- to 5-year olds reliably recalled sung words but not spoken words. The reliable LTM of sung words arose from hearing sung words during the initial learning rather than at test. Finally, the benefit of song on word learning and the reliable LTM of sung words observed at ages 3-5 cannot be explained as an attentional effect.
Keywords: Song; children; memory; speech; word learning.