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Infants don’t produce their first words until age one or later, but by
three or four, they can talk quite fluently about some topics. This development is one we take as much for granted as the infant’s transition from lying supine in the first few months to walking and running around by age one to two. Learning to talk is more complicated than learning to walk. Talking plays a major role in social communication and demands a grasp of all the local conventions of use in each speech community. Language use is an integral part of communication; it goes along with gesture, gaze, and other nonlinguistic means used to convey attitude and affect as well as speaker intentions.
As children learn to talk, they go through a series of stages, beginning with infancy, when they are unable to converse and do not yet understand any lan- guage. They go from babbling at seven to ten months old, to producing their first recognizable words six to twelve months later. Then, within a few months, they combine words and gestures, and produce their first word combinations around age two. This is followed by the production of ever more complex, adultlike utterances, as they become active participants in conversation, taking turns and making appropriate contributions. They begin to use language for a larger array of functions – telling stories, explaining how a toy works, persuading a friend to do something, or giving someone directions for how to get somewhere. Between age one and age six, children acquire extensive skills in using language and can sound quite adultlike much of the time. By around age ten to twelve, they have mastered many complex constructions, a good deal more vocabulary, and many uses of language.
Comprehension, throughout this process, tends to be far ahead of production. Children understand many words long before they can produce them, and this asymmetry between comprehension and production is lifelong: Consider the number of dialects adults can understand without being able to produce more than two or three at most. For a second language, consider how much better people are at understanding than at speaking. The same holds true for a first language: Comprehension remains ahead of production, but once production reaches a certain level, speakers tend to no longer notice any mismatch (yet it is still there). At the same time, mismatches play an important role in the process of acquisition: Children’s representations for comprehension provide targets for what their own production should sound like.
Is there continuity over stages? Do children try to express similar notions at successive points in development – whether issuing one word at a time, longer word combinations, or adultlike phrases? How much consistency is there in the stages children go through as they learn the same language? How much for children learning different languages? Do children from different social classes go through the same stages provided they are learning the same language? Are they all exposed to the same amount and same range of child-directed speech?