Bottom-up processes dominate early word recognition in toddlers.

This study set out to investigate whether the 'phonological onset preference effect' often reported in adult studies using the visual world task (i.e., increased attention to an object that is phonologically-related to a spoken-target word, such as boat-bear) is also contingent upon toddler participants having sufficient preview time to inspect the picture stimuli. Picture preview is thought to support the activation of phonological codes which can then be matched to the phonological representations extracted from incoming speech signals and the picture stimuli, supporting the 'phonological mapping hypothesis'. We found that both toddlers and adults were able to show an early phonological onset preference in short preview conditions, though, adults' early phonological onset preferences in the short preview condition was extinguished by the presence of a semantic competitor, replicating previous adult findings (Huettig & McQueen, 2007). Removal of a semantic competitor reinstated the phonological onset preference effect under short preview conditions for adults. Our findings indicate that toddlers are driven more by bottom-up, phonological information when selecting a referent in a visual world task, as compared to adults who are more inclined to exploit top-down, semantic information when directing their attention to a visual object, especially when there is insufficient preview time. We propose that, when implicit naming is improbable in short-preview conditions, a phonological onset preference effect is driven by mapping on the visual-semantic levels, which is more susceptible to top-down influences.