Studies of language acquisition often asume that children will simply begin to learn language, without questioning what sets the whole process in motion. In How Children Learn to Learn Language, Lorraine McCune thoroughly examines the often-neglected topic of how children discover the possibility of language and demonstrates that pre-language development involves a dynamic system of social, cognitive, and vocal variables that come together to enable the transition to referential language. The relationship with a caregiver is integral to this development because language is a system of symbolic communication that can emerge only with children's recognition that they are separate from others. McCune sees language learning as constructed equally from needing to develop meanings and learning to produce the sounds sequences that represent them. In order for this dual construction to be effective, however, children must discover their capacity to refer to objects and events in the world by having their internal states of focused attention accompanied by an autonomic, physiologically based vocalization, which is the grunt that results from physical or mental effort.
When the grunt is intensified and directed at a conversational partner, as when children attempt to convey an internal state, it becomes their first protoword.