4.5 Language: Development, Theories & Linguistic Relativity
Key Takeaways
- Language is built from phonemes (smallest sound units), morphemes (smallest meaning units), semantics, syntax, and pragmatics; MCAT questions routinely ask you to classify an error at the correct level.
- The nativist account (Chomsky) posits an innate language acquisition device and universal grammar, supported by overregularization errors such as "goed" that children never hear modeled.
- The learning/behaviorist account (Skinner) explains language through imitation and reinforcement but cannot explain novel utterances or the poverty of the stimulus.
- The weak Sapir-Whorf position (linguistic relativity) — language influences thought — has empirical support; the strong position (linguistic determinism) is largely rejected.
- Broca's aphasia is non-fluent with intact comprehension and preserved insight; Wernicke's aphasia is fluent but meaningless with impaired comprehension and little awareness of the deficit.
4.5 Language: Development, Theories & Linguistic Relativity
Language is the AAMC's designated bridge between cognition and social behavior, and it appears in Content Category 6B ("Making sense of the environment"). Passages typically describe a developmental study, a bilingual-cognition experiment, or a stroke patient with a specific speech deficit, then ask you to identify the theoretical framework or localize the lesion. Precision about terminology matters more here than in almost any other Psych/Soc topic.
The Structural Levels of Language
Language is hierarchically organized. Test writers deliberately describe an error at one level and ask you to name it.
| Level | Definition | Example | Example of a deficit |
|---|---|---|---|
| Phonemes | The smallest units of sound that distinguish meaning | The /b/ and /p/ that separate "bat" from "pat"; English uses roughly 40 | A Japanese speaker who cannot discriminate English /r/ and /l/ |
| Morphemes | The smallest units of meaning | "Cats" contains two: cat + plural -s | Dropping "-ed" and "-s" endings in agrammatic speech |
| Semantics | The meaning assigned to words and sentences | Knowing "physician" and "doctor" are near-synonyms | Substituting an unrelated word ("I ate a chair") |
| Syntax | The grammatical rules governing word order | "The nurse called the patient" differs from "The patient called the nurse" | Producing word salad with intact fluency |
| Pragmatics | Social rules of language use, including tone, register, and context | Speaking differently to an attending than to a toddler | Failing to recognize sarcasm or take conversational turns |
Prosody — the rhythm, stress, and intonation layered on top of speech — is a frequently tested add-on. Prosody carries emotional content and is largely a right-hemisphere function, which is why a left-hemisphere stroke can leave speech grammatically intact but emotionally flat, and why aprosodia is dissociable from aphasia.
Developmental Milestones
The AAMC expects approximate ages, not precise months. The sequence is universal across cultures and languages, which is itself an argument used by nativists.
- Crying and cooing (0–4 months): Vowel-like sounds; reflexive vocalization.
- Babbling (~4–6 months): Repetitive consonant-vowel strings ("bababa"). Critically, infants initially babble phonemes from all languages, then prune to the phonemes of their native language by roughly 10 months.
- One-word / holophrastic stage (~12 months): Single words carry whole-sentence meaning ("milk" = "I want milk").
- Telegraphic speech (~18–24 months): Two-word utterances stripped of function words ("want cookie," "daddy go"). Content words are retained; articles, prepositions, and auxiliaries are omitted.
- Overregularization / overgeneralization (~2–3 years): The child applies a newly learned rule too broadly, producing "goed," "runned," and "mouses." This is the single most cited developmental evidence in MCAT passages, because these forms are never modeled by adults — the child must be generating rules, not imitating.
- Critical (sensitive) period: Lenneberg proposed that native-level acquisition requires exposure before puberty. Cases of extreme deprivation, such as Genie, showed that vocabulary can be acquired late but syntax largely cannot.
Three Theories of Language Development
1. The Learning (Behaviorist) Theory — Skinner
Skinner's Verbal Behavior (1957) treated language as operant behavior: caregivers reinforce approximations of adult speech, and children imitate models. Language is therefore learned by the same principles as any other behavior.
- Strength: Accounts for vocabulary growth, accent acquisition, and pragmatics, which are clearly environmentally shaped.
- Fatal weaknesses tested on the MCAT: Children produce novel sentences they have never heard; parents reinforce truth value rather than grammar; and overregularization errors are not modeled. The poverty of the stimulus argument holds that the linguistic input a child receives is too impoverished and error-filled to explain the rich grammar they acquire.
2. The Nativist (Biological) Theory — Chomsky
Noam Chomsky argued that humans possess an innate, species-specific language acquisition device (LAD) — a biologically prepared mechanism that extracts grammatical rules from input. Underlying all human languages is a universal grammar, a shared deep structural framework; surface structures differ across languages while the deep structure does not.
- Supporting evidence: Universal milestone sequence; overregularization; the critical period; the emergence of full grammar in deaf children inventing sign systems; and the fact that the pace of acquisition is unrelated to explicit teaching.
- Key distinction: Chomsky claims language is acquired, not learned — a claim of readiness, not of predetermined content.
3. The Interactionist Theory — Vygotsky and Bruner
The interactionist position treats language as the product of biological readiness and social interaction. Bruner proposed a Language Acquisition Support System (LASS): the scaffolding caregivers supply through child-directed speech, joint attention, and turn-taking. Vygotsky's emphasis on socially mediated development places language squarely inside the zone of proximal development.
MCAT framing: If a passage emphasizes an innate mechanism, universal sequence, or grammar errors, the answer is nativist. If it emphasizes reinforcement or imitation, the answer is learning theory. If it emphasizes caregiver scaffolding or social context, the answer is interactionist.
The Influence of Language on Cognition
The Sapir-Whorf hypothesis claims that the language a person speaks shapes how they think. It comes in two strengths, and the MCAT tests the distinction directly:
- Strong version (linguistic determinism): Language determines thought; concepts without words are unthinkable. This version is largely rejected — people readily form concepts they have no word for.
- Weak version (linguistic relativity): Language influences habitual thought and attention. This version retains empirical support. Examples include speakers of languages with additional basic color terms discriminating those hues faster; languages using absolute (cardinal-direction) rather than egocentric spatial frames producing better dead-reckoning navigation; and grammatical gender biasing which adjectives speakers attribute to objects.
A recurring trap: a passage showing that bilinguals answer a question differently depending on the language of testing supports the weak version only. Read the answer choices for the word "determines" — that almost always marks the rejected strong version.
The Cortical Language Network and the Aphasias
| Syndrome | Lesion site | Fluency | Comprehension | Repetition | Insight into deficit |
|---|---|---|---|---|---|
| Broca's (expressive) | Left inferior frontal gyrus (Brodmann 44/45) | Non-fluent, effortful, agrammatic | Largely intact | Impaired | Preserved — patients are frustrated |
| Wernicke's (receptive) | Left superior temporal gyrus (Brodmann 22) | Fluent but semantically empty | Impaired | Impaired | Poor — patients are often unaware |
| Conduction | Arcuate fasciculus (connecting the two) | Fluent | Intact | Selectively impaired | Preserved |
| Global | Extensive left perisylvian damage | Non-fluent | Impaired | Impaired | Variable |
Because roughly 95% of right-handed individuals and the majority of left-handed individuals are left-hemisphere dominant for language, an MCAT passage describing acquired language loss will nearly always implicate a left-hemisphere lesion. If the passage instead describes flat, monotone speech with preserved grammar, think right-hemisphere aprosodia — not aphasia.
Exam Traps to Avoid
- Telegraphic speech is not agrammatic aphasia. Both drop function words, but telegraphic speech is a normal developmental stage in a toddler.
- Babbling is not imitation. Deaf infants babble manually, and hearing infants babble non-native phonemes, so babbling cannot be reinforcement-driven.
- The LAD is a mechanism, not a brain region. Do not equate it with Broca's area on a localization question.
- Overregularization signals rule acquisition, not regression. A child who says "went" then later says "goed" has advanced, not deteriorated.
A 30-month-old child who correctly said "I went to the store" three months ago now says "I goed to the store." Her pediatrician reassures the parents that this is a normal and even favorable developmental sign. Which theoretical claim does this observation most directly support?
Researchers find that speakers of a language with separate basic color terms for light blue and dark blue discriminate between those two hues faster than English speakers, though both groups can perceive the difference when given unlimited time. This finding best supports which position?
A 68-year-old patient is admitted after a stroke. He speaks in long, fluent, well-articulated sentences that contain invented words and convey no coherent meaning. He cannot follow simple spoken commands and appears untroubled by his communication difficulty. The lesion is most likely located in which structure?
An investigator argues that the linguistic input children receive is too fragmentary and error-filled to account for the sophisticated grammar they master by age five. This argument is known as the poverty of the stimulus, and it is most often deployed to challenge which account of language development?