The ability to predict future events based on past experience is crucial for cognitive functions like sensory processing and cognitive development. This chapter explores the relationship between predictive brain signals and language development, and how shared book reading experiences influence both. Predictive brain signals in infants aged 6, 12 and 18 months were measured using functional near-infrared spectroscopy (fNIRS) and the visual-omission paradigm. Strong correlations were found between the strength of these signals and both expressive vocabulary (at 12, 18, 26 and 47 months) and sentence complexity (at 18 and 30 months). Furthermore, shared book reading experiences reported by parents showed a significant correlation with predictive brain signals. This connection mediates the relationship between shared book reading experiences and children’s expressive vocabulary. The findings emphasize the important role of early experiences in shaping the neural mechanisms underlying language acquisition and highlight the potential of shared reading to enhance predictive brain activity, thereby fostering language development. However, limitations regarding the parent-reported nature of shared reading assessment warrant further investigation using more objective measures.