Early language acquisition: cracking the speech code

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EARLY LANGUAGE ACQUISITION: CRACKING THE SPEECH CODE

Patricia K. Kuhl

Abstract | Infants learn language with remarkable speed, but how they do it remains a mystery. New data show that infants use computational strategies to detect the statistical and prosodic patterns in language input, and that this leads to the discovery of phonemes and words. Social interaction with another human being affects speech learning in a way that resembles communicative learning in songbirds. The brains commitment to the statistical and prosodic patterns that are experienced early in life might help to explain the long-standing puzzle of why infants are better language learners than adults. Successful learning by infants, as well as constraints on that learning, are changing theories of language acquisition.

The acquisition of language and speech seems deceptively simple.Young children learn their mother tongue rapidly and effortlessly, from babbling at 6 months of age to full sentences by the age of 3 years, and follow the same developmental path regardless of culture (FIG. 1). Linguists, psychologists and neuroscientists have struggled to explain how children do this, and why it is so regular if the mechanism of acquisition depends on learning and environmental input. This puzzle, coupled with the failure of artificial intelligence approaches to build a computer that learns language, has led to the idea that speech is a deeply encrypted code. Cracking the speech code is childs play for human infants but an unsolved problem for adult theorists and our machines.Why?

During the last decade there has been an explosion of information about how infants tackle this task. The new data help us to understand why computers have not cracked the human linguistic code and shed light on a long-standing debate about the origins of language in the child. Infants strategies are surprising and are also unpredicted by the main historical theorists. Infants approach language with a set of initial perceptual abilities that are necessary for language acquisition, although not unique to humans. They then learn rapidly from exposure to language, in ways that are unique to humans, combining pattern detection and computational abilities (often called STATISTICAL LEARNING) with

special social skills. An absence of early exposure to the

patterns that are inherent in natural language whether spoken or signed produces...