Some languages describe musical pitch in terms of spatial height; others in terms of thickness. Differences in pitch metaphors also shape adults’ nonlinguistic space-pitch representations. At the same time, 4-month-old infants have both types of space-pitch mappings available. This tension between prelinguistic space-pitch associations and their subsequent linguistic mediation raises questions about the acquisition of space-pitch metaphors. To address this issue, 5-year-old Dutch children were tested on their linguistic knowledge of pitch metaphors, and nonlinguistic spacepitch associations. Our results suggest 5-year-olds understand height-pitch metaphors in a reversed fashion (high pitch = low). Children displayed good comprehension of a thickness-pitch metaphor, despite its absence in Dutch. In nonlinguistic tasks, however, children did not show consistent space-pitch associations. Overall, pitch representations do not seem to be influenced by linguistic metaphors in 5-year-olds, suggesting that effects of language on musical pitch arise rather late during development.

Infants' bodies, brains, and environments are ever-changing. Although this continuous transformation is a fundamental feature of development, how infants actively adapt and learn amidst such volatility is still unknown. To address this, we devised a novel learning task in which the location of a reward was systematically altered, transitioning from stable to volatile periods. Through computational modelling, we inferred from the infants' gaze and pupil data the learning processes that enabled them to navigate these changing environments. We found that infants' tonic pupil size reflected trial-by-trial changes in the level of environmental volatility. Moreover, phasic changes in pupil size when observing the reward indicated that infants relied on the information about volatility to optimize their learning. This resulted in the successful performance of the task, as indicated by the pattern of anticipatory looks to the correct reward locations. Together, these results identify the active role that infants play in adapting to change.

The ‘sense of agency’—the feeling of doing—is a phenomenological experience that cannot be taken for granted in infants. Researching the development of this phenomenon hinges on its conceptualization. Although it may seem natural to ask “When do infants have sense of agency?”, this binary view on the presence (or absence) of a sense of agency seems conceptually problematic. Cognitive phenomenological research reveals that sense of agency is a complex set of agentive experiences with different contents (e.g. ‘the experience of acting’, ‘the experience of volition’) that are often conflated. Given that different contents presuppose different representational capacities, developmental psychology may better target the question “What senses of agency can infants have at different developmental stages?” We show how this re-conceptualization impacts the interpretation of existing empirical findings in infant research, and how it can improve our understanding of the developmental trajectory of infants’ experiences of agency.