Kobayashi, T. 1 & Murase, T. 2
1 NTT Communication Science Labs
2 Shimane University
Recent habituation studies have shown that English-learning 12-month-olds can rapidly associate one label with one object, suggesting that their word-learning mechanism works efficiently from the earliest stage of lexical development (MacKenzie et al., 2012). However, infants do not necessarily hear one label for one object in particular linguistic environments. For example, Japanese children often hear two different labels from infant- and adult-directed speech (e.g., wanwan and inu for a dog), and bilingual children often hear two labels from different languages for one object. An unresolved issue is thus how infants process two labels for one object. This study focuses on Japanese children with extensive multiple-labeling experience to examine whether 12-month-olds can rapidly associate two novel words with one object in a habituation paradigm with a switch design (Werker et al., 1998). Monolingual Japanese-learning 12-month-olds (N=48, mean age=12.4, range: 12.0-12.9) were habituated to two computer-animated scenes in which one novel object was paired with two novel labels embedded in sentence frames (e.g., Look, [it]'s a ronron. [It]'s a yamitsu). While the infants in one condition heard two novel words phonologically characteristic of an infant-directed speech (IDS) word (ronron, tenten) and an adult-directed speech (ADS) word (tawa, yamitsu), those in the other condition heard only two novel ADS words (tawa, yamitsu, byoku, reroni). After being habituated to the two scenes, they were given two 'same' trials and two 'switch' trials. In the test trials, only one label was presented to assess each word-object association. Results show that the 12-month-olds in both conditions looked equally long in the 'same' and 'switch' trials, indicating that 12-month-olds cannot yet learn labels. A follow-up experiment with 12-month-olds (N=24) found that they formed word-object associations when one object was paired with one ADS word. Together, these findings suggest that presenting 12-month-olds with multiple labels hinders word-object associations.