Language Acquisition in psychology refers to the process by which humans acquire the ability to perceive, produce, and use words to understand and communicate.

This innate capacity typically develops in early childhood and involves complex interplay of genetic, cognitive, and social factors.

My project 1 51 — Language is a cognition that truly makes us human. Whereas other species do communicate with an innate ability to produce a limited number of meaningful vocalizations (e.g., bonobos) or even with partially learned systems (e.g., bird songs), there is no other species known to date that can express infinite ideas (sentences) with a limited set of symbols (speech sounds and words).

In This Article:

Behaviorist Theory of Language Acquisition

The behaviourist theory of language acquisition, developed principally by B.F. Skinner, holds that language develops entirely through environmental input rather than any innate biological endowment.

In Verbal Behavior (1957), Skinner argued that speech is a product of behavioural history: children learn to communicate through the same principles of operant conditioning that govern other learned behaviours.

Skinner proposed that verbal behaviour emerged evolutionarily because human vocal musculature became susceptible to conditioning.

In practice, an infant’s early, unplanned vocalisations — cooing and babbling — are gradually shaped by caregivers into recognisable words through selective reinforcement.

Adults reward approximations of real words and ignore meaningless sounds, progressively refining those words into grammatically structured speech.

Key Mechanisms

The behaviourist model identifies several routes through which language is conditioned:

Positive reinforcement: Children learn that specific vocalisations produce desired outcomes. Skinner termed these requests mands: if a child says “water” and receives a drink, that vocalisation is reinforced by its consequence.
Social reinforcement: Parental responsiveness — praise, eye contact, touch — makes vocalisation itself rewarding, sustaining the child’s motivation to communicate.
Imitation and tacts: Children emit echoic responses (imitations of adult speech) and tacts (verbal labels for objects and events). Accurate imitation and labelling attract parental approval, incrementally bringing the child’s output closer to adult norms.

Supporting Evidence

Conditioning principles demonstrably influence early language.

Brodbeck and Irwin (1946) found that children whose vocalisations received parental reinforcement vocalised more frequently.

More compellingly, Lovaas (1987) showed that operant techniques could systematically teach language to children with autism and other developmental disorders.

Evidence that reinforcement-based shaping can produce functional linguistic behaviour even where typical acquisition has failed.

Criticisms and Limitations

Despite its clinical utility, behaviourism offers an inadequate account of language acquisition, and Noam Chomsky’s critique remains the most incisive.

Productivity. Language is generative: speakers routinely produce and comprehend sentences they have never encountered before (Chomsky, 1968). A model based on reinforcing prior responses cannot explain this creativity.
Grammar acquisition. Parents typically respond to the meaning of a child’s utterance rather than its grammatical form — answering “Why the dog won’t eat?” without correcting its syntax. It is therefore unclear how correct grammar is selectively reinforced. Furthermore, when children do imitate adult speech, they tend to reduce it to telegraphic forms consistent with their current developmental grammar rather than reproducing the adult model.
Universality. Children across all cultures and languages pass through an invariant sequence of developmental stages. Environmental input varies enormously; the sequence does not. Reinforcement history alone cannot account for this uniformity.
Sentence comprehension. Understanding a sentence involves more than summing the meanings of its component words — a complexity that operant conditioning cannot address.

Conclusion

Reinforcement, imitation, and environmental input undoubtedly shape vocabulary and accent.

However, the pure behaviourist account is now widely regarded as insufficient.

Most contemporary researchers view language acquisition as the product of both environmental interaction and innate biological predispositions: a position that behaviourism, in its original form, was never equipped to accommodate.

Chomsky Theory of Language Development

Noam Chomsky’s theory of language acquisition fundamentally reoriented the field by shifting focus from environmental conditioning to innate biological endowment.

In the spirit of the cognitive revolution in the 1950s, Chomsky argued that children would never acquire the tools needed for processing an infinite number of sentences if the language acquisition mechanism was dependent on language input alone.

Noam Chomsky introduced the nativist theory of language development, emphasizing the role of innate structures and mechanisms in the human brain. Key points of Chomsky’s theory include:

Language Acquisition Device (LAD): Chomsky proposed that humans have an inborn biological capacity for language, often termed the LAD, which predisposes them to acquire language.
Universal Grammar: He suggested that all human languages share a deep structure rooted in a set of grammatical rules and categories. This “universal grammar” is understood intuitively by all humans.
Poverty of the Stimulus: Chomsky argued that the linguistic input received by young children is often insufficient (or “impoverished”) for them to learn the complexities of their native language solely through imitation or reinforcement. Yet, children rapidly and consistently master their native language, pointing to inherent cognitive structures.
Critical Period: Chomsky, along with other linguists, posited a critical period for language acquisition, during which the brain is particularly receptive to linguistic input, making language learning more efficient.

Critics of Chomsky’s theory argue that it’s too innatist and doesn’t give enough weight to social interaction and other factors in language acquisition.

Criticisms

Chomsky’s framework, despite its influence, has attracted substantial criticism.

The role of social interaction: Critics argue that Chomsky underestimated how much the social environment contributes to acquisition. Grammatical structure is acquired gradually over years, and the responsive, simplified speech caregivers direct at children — sometimes called child-directed speech — provides scaffolding that goes well beyond what an innate device alone could explain.
The plausibility of Universal Grammar: Others find the claim of a universal, innate grammar difficult to sustain given the sheer structural diversity of human languages, from English and Japanese to Turkish and signed languages. Accounting for all of these within a single innate system requires increasingly abstract and contested formulations.
Exceptions to recursion: The most pointed empirical challenge comes from Pirahã, an Amazonian language reportedly lacking embedded clauses altogether. If recursion were truly a universal property of human language, such exceptions should not exist.

Acquisition Support System (LASS)

How does Bruner’s LASS theory complement Chomsky’s LAD?

Jerome Bruner’s Language Acquisition Support System (LASS) was developed as a direct complement to Chomsky’s Language Acquisition Device (LAD) — not to replace it, but to supply what it conspicuously lacked: an account of the social and environmental conditions that make an innate linguistic capacity functional.

Where Chomsky focused on the internal biological mechanism, Bruner focused on the interpersonal scaffolding that activates it.

The Theoretical Gap

Chomsky’s LAD posits that children are born with an innate grasp of universal grammar and the capacity to map underlying meanings onto spoken surface structures.

Because the language children hear is often incomplete or ungrammatical, Chomsky argued that environmental input alone cannot explain the speed and success of acquisition — the LAD must do the heavy lifting, with the environment serving merely as a passive trigger.

What this account leaves unexplained is the richness and structure of the input children actually receive.

Subsequent researchers noted that exclusive focus on the child’s internal endowment neglects the organised, responsive character of adult-child interaction — and that caregivers provide far better linguistic scaffolding than Chomsky’s model assumed. This is the gap Bruner’s LASS is designed to fill.

How the LASS Complements the LAD

From passive input to active facilitation.

Chomsky treated caregivers primarily as providers of raw linguistic data for the LAD to process.

Bruner argued this misrepresents what caregivers actually do.

Adults do not simply speak in the child’s presence; they calibrate their language to the child’s current level, simplify and segment input, and structure interactions to give the child manageable material to practise and extend.

Moerk’s pointed observation — that “the LAD was a lady” — captures this: the structured, responsive linguistic work Chomsky attributed to an internal device was in large part being performed by the mother or caregiver all along.

Bridging syntax and pragmatics.

The LAD, as Chomsky conceived it, is a syntactic engine: its concern is how grammatically well-formed sentences are constructed.

Bruner’s LASS addresses a different and equally important question — what language is for.

Bruner argued that entering language means entering discourse: the child must learn not only how to produce grammatical structures but how to use them to realise intentions, interpret others’ communicative acts, and participate in genuine dialogue.

Grammar without pragmatics produces sentences; grammar with pragmatics produces communication.

The role of pre-linguistic interaction.

Bruner situated formal language development within a longer history of non-verbal exchange.

Long before a child produces grammatical speech, caregiver and infant establish shared routines — turn-taking, joint attention, coordinated emotional response.

These formats are not incidental to language acquisition; they are its foundation.

The LAD may specify how sentences are constructed; the LASS ensures the child understands what sentences are for and how to deploy them in relation to another person.

The LAD and LASS in Concert

The two frameworks address different aspects of the same phenomenon and are most coherent when read together.

Chomsky’s LAD supplies the biological endowment — the innate grammatical potential without which no amount of social interaction would produce human language.

Bruner’s LASS supplies the structured environment that directs that potential toward actual communicative use.

Neither is sufficient alone: an LAD without a LASS yields a grammatical capacity with nowhere to go; a LASS without an LAD cannot explain why children converge on complex grammatical systems despite enormous variation in their social environments.

Cognitive Approach to Language Acquisistion

The cognitive approach to language acquisition, associated principally with the Swiss psychologist Jean Piaget, rests on a single organising claim: thought precedes language.

Language is not an autonomous faculty but an expression of underlying cognitive development.

Rather than shaping a child’s understanding of the world, language maps onto conceptual structures the child has already built through interaction with their environment.

Schemas and Cognitive Readiness

Central to Piaget’s account is the schema: a mental structure encoding knowledge about a particular aspect of the world.

Piaget was a constructivist — he believed children actively build these frameworks through physical and mental engagement with their surroundings, rather than passively receiving them from the environment or inheriting them biologically.

On this view, a child acquires a word by attaching it to a concept already represented in their thinking. The concept must come first.

A child taught a word before grasping its underlying meaning will reproduce it without comprehension — parroting a sound rather than using a symbol.

Cognitive readiness, not linguistic exposure, is the limiting factor.

Schema development is driven by two complementary processes:

Assimilation: incorporating new experiences into existing schemas.
Accommodation: revising existing schemas, or constructing new ones, when new experiences cannot be absorbed into current frameworks.

Steven Pinker

Steven Pinker argues that language is a biological instinct — not a cultural invention, a learned skill, or an accidental byproduct of general intelligence, but an evolved capacity hard-wired into the human brain.

Drawing on evolutionary psychology, he contends that language emerged through natural selection precisely because it promoted survival and reproduction, and that understanding it requires situating it within the long arc of human evolutionary history.

The Evolutionary Basis of Language

Pinker’s starting point is that modern human cognition — including language — reflects mental architecture shaped during roughly three million years of hunter-gatherer existence.

This leads him to a direct challenge to what he calls the “standard social science model”: the assumption that the mind is a blank slate wholly formed by culture.

On the contrary, Pinker argues, the mind contains genetically encoded, domain-specific capacities, of which language is the clearest example.

Pinker and Chomsky: Agreement and Divergence

Pinker endorses Chomsky’s Language Acquisition Device — the proposal that children possess an innate linguistic mechanism that explains the speed and ease with which they acquire language without formal instruction.

On this much, the two agree.

Their disagreement is fundamental, however.

Chomsky treats the language faculty as a distinct mental module that arose independently of general cognition and was not directly shaped by natural selection — possibly co-opted from some prior cognitive function.

Pinker rejects this entirely.

For him, language evolved through natural selection as an adaptive trait.

Even if the language faculty recruited pre-existing cognitive machinery, as Chomsky allows, Pinker argues that natural selection progressively modified those structures specifically to support complex linguistic communication.

The distinction matters: for Chomsky, language’s adaptive value is incidental; for Pinker, it is the explanation.

Mentalese and the Rejection of Linguistic Relativity

At the centre of Pinker’s account is the concept of Mentalese: a universal, innate language of thought that underlies and precedes spoken language.

He proposes that humans share a fixed mental vocabulary of basic conceptual categories — space, time, force, causation — and that the spoken languages of the world are surface expressions of this shared cognitive substrate.

This commitment leads Pinker to reject the Linguistic Relativity Hypothesis (the Sapir-Whorf hypothesis), which holds that the specific language a person speaks shapes or constrains their thought.

Pinker inverts the relationship: it is Mentalese — the evolutionarily derived language of thought — that shapes spoken language, not the other way around.

Cognitive Architecture: Verbs and Dual Processing

Pinker uses verb structure to illustrate how the mind innately categorises the world.

The contrast between “pour wine into the glass” and the unacceptable “fill wine into the glass” reflects an automatic cognitive distinction between actions driven by gravity and actions driven by other forces — a categorisation the speaker does not consciously apply but cannot violate.

At a processing level, Pinker proposes a dual architecture for language:

Regular verbs (walk/walked) are handled by a rule-based symbolic system: a generalised grammatical operation applied to novel forms.
Irregular verbs (hide/hid, ride/rode) are handled by a connectionist system: pattern recognition and associative memory rather than rule application.

This hybrid model reflects Pinker’s broader view that the mind is not a single, uniform system but a collection of specialised mechanisms — some rule-governed, some associative — each shaped by distinct evolutionary pressures.

Relation to Other Theories

Pinker’s position intersects with Piaget’s cognitive approach in one limited but noteworthy respect: both treat language as rooted in deeper cognitive and evolutionary structures rather than as a self-contained system.

For Piaget, those structures are built through individual development.

For Pinker, they are inherited through evolution.

The agreement is on the dependency of language on something prior — the explanation of what that prior thing is, and how it came to be, separates them sharply.

Stages of Language Acquisition

Regardless of cultural background or native language, children progress through a strikingly predictable sequence of stages in language acquisition.

This universality is itself theoretically significant: it suggests the developmental trajectory is biologically constrained rather than purely a product of environmental variation.

Even before birth, infants demonstrate sensitivity to language — showing a preference for their mother’s voice and the ability to discriminate her language from unfamiliar ones.

1. The Prelinguistic Stage (0–12 months)

In their first year, infants communicate through vocalisations and gesture rather than language proper.

This stage is not merely a precursor to language but an active period of perceptual and motor preparation.

Early vocalisations. Crying dominates the first month, functioning as a reflexive signal of internal states. Even at this stage, infants can discriminate between speech sounds (phonemes) — a capacity that precedes any productive language.
Phonemic expansion. By around two months, infants can produce every phoneme found across the world’s languages, regardless of which language surrounds them.
Babbling. Between three and nine months, infants begin producing repetitive consonant-vowel combinations — “ma”, “da” — in what is known as the babbling stage. Crucially, infants raised in signing environments produce equivalent manual babbling with their hands, suggesting the underlying drive is biological rather than specific to the vocal-auditory channel.
Phonemic contraction and echolalia. At around nine to ten months, infants undergo phonemic contraction: they cease producing universal sounds and restrict their repertoire to the phonemes of their native language. Around the first birthday, this shifts into echolalia — the rhythmic, speech-like repetition of syllables such as “dadadada” — which bridges babbling and meaningful speech.

2. The One-Word Stage (12–18 months)

Most children produce their first recognisable word between twelve and eighteen months.

Early vocabulary tends to be phonologically simple, invented in part, and highly context-dependent — typically anchored to familiar nouns: family members, animals, food.

At this stage, receptive vocabulary (words understood) substantially exceeds expressive vocabulary (words produced).

A defining feature of this stage is holophrastic speech: single words that carry communicative weight far exceeding their literal content.

“Milk” might identify the substance, request more of it, or report that it has been spilled.

The full intended meaning is conveyed through gesture, intonation, and shared context rather than linguistic structure alone.

3. The Two-Word Stage / Stage 1 Grammar (18–30 months)

As vocabulary grows, children begin combining words into minimal sentences.

This speech is characteristically telegraphic: only words carrying core semantic content are produced — typically nouns and verbs — while grammatical functors (articles, copulas, plural markers, tense inflections) are systematically omitted.

“Drawing dog” stands in for “I am drawing a dog.”

Despite this stripped-down form, children maintain a consistent word order, preserving meaning through syntax even in the absence of morphological markers.

This is not random omission but reflects an early sensitivity to grammatical structure.

4. Stage 2 Grammar and Beyond (30 months onwards)

From around thirty months to age five, vocabulary grows rapidly and children begin mastering the grammatical apparatus absent from their earlier speech.

Mean Length of Utterance (MLU) increases as functors — conjunctions, tense inflections, plurals — are progressively incorporated.

A particularly revealing phenomenon at this stage is overgeneralisation (or over-regularisation): children apply newly acquired grammatical rules to irregular forms that are exceptions.

Having inferred that past tense is formed by adding -ed, a child will produce “runned” or “costed”; having learned that plurals take -s, they produce “mouses” or “gooses”.

These errors are theoretically important — they demonstrate that children are extracting and applying abstract rules, not simply imitating the speech around them.

Imitation would produce correct irregular forms; overgeneralisation proves rule induction.

By age four or five, children have mastered the core grammar of their language, sustain multi-turn conversation, and command a receptive vocabulary of several thousand words.

An acquisition feat accomplished, for the most part, without explicit instruction.

References

Ambridge, B., & Lieven, E.V.M. (2011). Language Acquisition: Contrasting theoretical approaches. Cambridge: Cambridge University Press.

Chomsky, N. (1965). Aspects of the Theory of Syntax. MIT Press.

Pine, J.M., Conti-Ramsden, G., Joseph, K.L., Lieven, E.V.M., & Serratrice, L. (2008). Tense over time: testing the Agreement/Tense Omission Model as an account of the pattern of tense-marking provision in early child English. Journal of Child Language, 35(1): 55-75.

Rowland, C. F.; & Noble, C. L. (2010). The role of syntactic structure in children’s sentence comprehension: Evidence from the dative. Language Learning and Development, 7(1): 55-75.

Skinner, B.F. (1957). Verbal behavior. Acton, MA: Copley Publishing Group.

Theakston, A.L., & Lieven, E.V.M. (2005). The acquisition of auxiliaries BE and HAVE: an elicitation study. Journal of Child Language, 32(2): 587-616.

Language Acquisition Theory