Cognitive Connie
What is language acquisition?
Language is the most complex cognitive system a human being ever acquires — and most children master the fundamentals of their native tongue by the age of four or five, without formal instruction and across widely varying linguistic environments. How this remarkable achievement is possible is one of the central questions of cognitive science.
Defining features
01. Predictable stages
From babble to fluency.
Language develops in a broadly predictable sequence, though timing varies. Each stage builds on the last, reflecting both growing neural maturity and increasing exposure to language in social contexts.
Pre-linguistic Stage
Infants begin life sensitive to all speech sounds across all languages. By 6 months, they start to specialise for the phonemes of their native language. Cooing, gurgling, and early turn-taking in vocalisations are precursors to language.
Canonical Babbling
Reduplicated babbling (ba-ba-ba, ma-ma-ma) emerges at around 6–8 months and gradually becomes variegated, reflecting the phonological patterns of the ambient language. Deaf children exposed to sign language babble manually.
One-Word (Holophrastic) Stage
Single words carry the communicative load of whole sentences. First words are typically object labels ('mama', 'cup', 'dog'). Overextension (calling all men 'dada') and underextension (reserving 'dog' only for the family pet) are common errors.
Telegraphic Speech
Two-word combinations emerge, conveying basic semantic relations ('more milk', 'daddy go', 'no bed'). Function words are absent. A vocabulary explosion often accompanies this period, with children learning several new words per day.
Key figures
B.F. Skinner
1904–1990Proposed a behaviourist account of language in Verbal Behaviour (1957), arguing children learn through imitation and reinforcement. Chomsky's devastating review effectively ended behaviourism as a mainstream account of language acquisition.
Jerome Bruner
1915–2016Proposed the Language Acquisition Support System (LASS) as a social complement to Chomsky's LAD — highlighting the essential role of caregiving routines, joint attention, and scaffolded interaction in language development.
Eric Lenneberg
1921–1975Proposed the critical period hypothesis for language acquisition in Biological Foundations of Language (1967), arguing that the brain's language-learning capacity is most plastic before puberty.
Noam Chomsky
1928–presentAmerican linguist who proposed the Language Acquisition Device and Universal Grammar, radically shifting the field away from behaviourist accounts. His 1959 critique of Skinner's Verbal Behaviour is among the most influential texts in cognitive science.
Key concepts
Language Acquisition Device (LAD)
Chomsky's proposed innate mechanism that allows children to extract the grammatical rules of their native language from surrounding input. The LAD is hypothesised to contain Universal Grammar — abstract, cross-linguistic structural principles that constrain the space of possible human languages.
Universal Grammar
The hypothesis, central to Chomsky's linguistics, that all human languages share a set of underlying structural principles — and that these principles are part of the biological endowment of the human species rather than learned from experience.
Critical period hypothesis
Eric Lenneberg's proposal that language acquisition must occur within a biologically determined window (roughly from birth to puberty) during which the brain is maximally plastic. Evidence comes from second-language acquisition — native-like fluency becomes harder after puberty — and cases of extreme linguistic deprivation.
Poverty of the stimulus
Chomsky's argument that the linguistic input children receive is insufficient — too sparse and inconsistent — to explain the rich grammatical knowledge they ultimately acquire. This 'poverty' argues for an innate contribution to language knowledge.
Child-Directed Speech (CDS)
The simplified, higher-pitched, slower, more repetitive speech register (sometimes called 'motherese' or 'parentese') that adults across cultures use when addressing young children. CDS may help children segment speech into words and identify grammatical patterns.
Language Acquisition Support System (LASS)
Jerome Bruner's term for the social scaffolding that caregivers provide to support language development — interactive routines such as joint attention, turn-taking, and naming games that create the supportive linguistic environment Chomsky's nativist account largely ignores.
Overextension and underextension
Two common error patterns in early word learning. Overextension: applying a word too broadly ('dog' for all four-legged animals). Underextension: applying a word too narrowly ('cup' only for the child's own cup). Both reflect how children test and refine their mapping of words to concepts.
Phonological development
The gradual acquisition of the sound system of a language. Infants begin as 'universal listeners' sensitive to all phonemic contrasts, then narrow to the distinctions in their native language by 6–12 months. Most native phoneme contrasts are mastered by 4–5 years.
Test your knowledge
Sources
Last reviewed July 2025- 1.
Chomsky N. (1965). Aspects of the Theory of Syntax. MIT Press.
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Introduced universal grammar and the language acquisition device, foundational for the nativist account of language learning.
- 2.
Tomasello M. (2003). Constructing a Language: A Usage-Based Theory of Language Acquisition. Harvard University Press.
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Leading alternative to nativism, arguing that language is acquired through general social-cognitive and learning mechanisms.
- 3.
Hoff E. (2014). Language Development (5th ed.). Wadsworth.
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Comprehensive textbook covering developmental trajectories from babbling through complex grammar.