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Synthesized speech technology holds potential for enabling natural conversations between humans and machines, particularly in social robotics. However, the combination of synthesized speech with social robots still lacks some qualities of natural speech, which is crucial for human robot interactions, especially for children. In this study, we recorded the neural activity of 5-year-old, typically developing children from middle to high socio-economic households using EEG while they listened to stories narrated by either an adult or a social robot, specifically Furhat. We measured cortical speech tracking to compare how well children's brains tracked synthesized speech from a robot compared to natural speech from an adult. Our results suggest that children do indeed show cortical speech tracking in both scenarios. The results also suggest that cortical speech tracking requires larger time delays between the speech and the response to reach its peak in child-robot interaction compared to child-adult interaction. Possible sources of these differences along with their implications are discussed.

While previous studies highlight the role that children’s interest in natural categories predict their learning of new label-object associations in these categories, the long-term implications of such a relationship – the extent to which children’s interest shape lexical development – remain unclear. The current study examines whether children’s interests in different natural object categories predict their subsequent interest and the number of words children know in those categories six months later. Using data from sixty-seven children tested at eighteen and twenty-four months of age, we found that parents’ estimates of interest in natural object categories at 18-months predicted their reports of their child’s interests at 24-months. Parent interest reports at 18-months also predicted the number of words that children are reported to know in that category at 24-months. Taken together, this study documents the longitudinal relationship between children’s interests, parents’ awareness of their children’s interests and later vocabulary development.

Research showcases children’s active role in steering their learning progress by choosing what, when and whom to learn from. Here, we examined differences in children’s preferred way to sample their environment and the extent to which children’s sampling preferences predict learning outcomes. During training, 3- and 6-year-olds chose whether they wanted to actively sample objects (whose labels they would be presented with) or passively view a set of object-label associations. Following this choice, they were then presented with novel object-label associations in the chosen manner. We found that when given the choice to learn in their preferred manner, children who had a reduced preference for active sampling learned better in the passive condition. This effect was more pronounced in younger children. Our findings highlight the dynamics of children’s active learning, with children’s learning outcomes being influenced by how they choose to sample their environment. Children are not just active in terms of choosing what to learn but also accurately estimate how they ought to sample their environment.

There is an established body of research showing that both the quality and quantity of caregiver input plays an integral role in infants’ language development. Equally, infants play an active role in eliciting that input, with their interests also guiding what they learn. In this study, we examined monolingual German children to see whether caregivers’ perception of their child’s interest predicts the quality of caregiver speech as well as infant vocalisations during a shared book-reading interaction at two timepoints, 18 months and 24 months. We also aimed to examine longitudinal changes in prosodic qualities of infant-directed speech over infant development. Caregivers read two books to their child, one of which they rated to be of high interest to their child, while the other was rated to be of low interest to the child. We measured the pitch range, mean pitch and duration of caregiver utterances as well as the number of infant vocalisations during the book reading sessions. We found that the duration of utterance varied significantly, with caregivers producing shorter utterances when reading high interest books to their child at 18 months and producing longer utterances reading high interest books to their older, 24-month-old infant. Infants also vocalised more during high interest books, which we interpret in terms of their active elicitation of information during reading. Longitudinally, we observed that pitch range increased and mean pitch decreased (approaching adultdirected speech), aligning with previous research on infantdirected speech. These findings help underscore the dynamic feedback loops of caregiver-child interactions which play a pivotal role in early development, with children seeking information and caregivers responding contingently.

There is a long-standing debate on the extent to which early word learning is shaped by the child’s existing lexical knowledge relative to the child’s environment. We investigated the influence of the connectivity of words in the child’s lexicon (preferential attachment), the child’s environment (preferential acquisition), or between novel and known words (lure of associates) in the development of early phonological and semantic networks, using longitudinal data from 17-to-36-monthold Norwegian children. We compared the extent to which the different scenarios predicted individual children’s lexical acquisition whilst also examining the joint influence of form and meaning on vocabulary growth. Our results revealed a ‘rich-get-richer’ pattern whereby semantically well-connected words in children’s existing lexicons best predicted the likelihood of a word entering the lexicon earlier. Phonological connectivity tended to impede word learning, with leveraging effects only in early development when semantic connectivity was low. Our findings imply that words are learned more easily when they are similar to many words in meaning, but not, necessarily, in form. Furthermore, relative to previous studies examining the influence of phonological connectivity on word learning, our study highlights the importance of considering the interplay between semantics and phonology and accounting for individual differences in vocabulary development.