Much of our basic understanding of cognitive and social processes in infancy relies on measures of looking time, and specifically on infants’ visual preference for a novel or familiar stimulus. However, despite being the foundation of many behavioral tasks in infant research, the determinants of infants’ visual preferences are poorly understood, and differences in the expression of preferences can be difficult to interpret. In this large-scale study, we test predictions from the Hunter and Ames model of infants' visual preferences. We investigate the effects of three factors predicted by this model to determine infants’ preference for novel versus familiar stimuli: age, stimulus familiarity, and stimulus complexity. Drawing from a large and diverse sample of infant participants (N = XX), this study will provide crucial empirical evidence for a robust and generalizable model of infant visual preferences, leading to a more solid theoretical foundation for understanding the mechanisms that underlie infants’ responses in common behavioral paradigms. Moreover, our findings will guide future studies that rely on infants' visual preferences to measure cognitive and social processes.

This systematic review surveys research on the associations between sleep and the memory processes involved in word learning in infancy. Only 16 studies were found to address this topic directly, identifying associations between infant sleep, the identification of word forms in running speech and the stabilisation and generalisation of new word form-meaning associations. Some studies investigated changes in brain responses after word learning and in sleep parameters during post-learning sleep. Others investigated the long-term effects of sleeping patterns on later vocabulary development. All but one of these studies identified positive associations between sleep and word learning in early childhood, extending similar findings in adults and school-aged children. However, there remain several gaps in the current research on early lexical development and sleep; future investigations should address these gaps to better understand lexical development and to create links between memory and language acquisition research.

This systematic review surveyed research on the associations between sleep and the memory processes involved in word learning in infancy. We found only 16 studies that addressed this topic directly, identifying associations between infant sleep and the memory processes, the identification of word forms in running speech, and the stabilization and generalization of new word form-meaning associations. Some studies investigated changes in brain responses after word learning and in sleep parameters during postlearning sleep. Others investigated the long-term effects of sleeping patterns on later vocabulary development. All but one of these studies identified positive associations between sleep and word learning in early childhood, extending similar findings from studies on adults and school-aged children. However, there remain several gaps in the current research on early lexical development and sleep. Future investigations