Exploring Variation in Infants' Preference for Infant-directed Speech: Evidence From a Multi-Site Study in Africa

Infants show a preference for infant-directed speech (IDS) over adult-directed speech (ADS). This preference has been linked to infants' language processing and word learning in experimental settings, and also correlates with later language outcomes. Recently, the cross-cultural consistency of infants' IDS preference has been confirmed by large-scale, multisite replication studies, but conclusions from these studies were primarily based on participants from North America and Europe. The current study addressed this sampling bias via a large-scale, multisite study of infants (3-15 months) across communities in Africa. We investigated whether participants showed a preference for IDS over ADS, and if so, whether the magnitude of their preference differs from effects documented in other populations of infants. Across six sites (total N = 200), we observed a preference for IDS over ADS ( ${\hat{\beta }}_{\mathrm{IDS}\mathrm{vs}.\mathrm{ADS}}$ = 0.06), suggesting that infants look on average 6% longer on the IDS trials than the ADS trials. There was no significant difference between African infants in this study and a method-matched subsample of infants from prior studies of IDS preference. This study provides new evidence on the generalizability of IDS preference and looking-time methods more broadly, while also highlighting some of the challenges of global big team science. SUMMARY: This study demonstrates a reliable infant-directed speech preference among African infants aged 3-15 months using a large-scale, multisite experimental design. Our findings showed no significant difference in IDS preference magnitude between African infants and method-matched samples from prior North American and European MB1 studies. Our study provides evidence for the cross-cultural generalizability of IDS preference while identifying practical challenges of conducting international multisite developmental research.