Infancy is a sensitive period for language development. “When and how do humans acquire language?” is an important question for understanding developmental mechanisms and trajectories of language. However, this point remains poorly understood. In the current paper, I focused on the idea that social cognition is a key component of language acquisition, and reviewed the relationship between the audiovisual integration of speech (i.e., speech perception) and language development in infancy. I further discussed how factors such as parenting (i.e., adults’ speaking style) and preterm birth influence the development of speech perception and language. Based on these reviews, I proposed developmental mechanisms from speech perception to language acquisition and the future perspective of language development research.