01 / 21

Communication &
Language Development

Explore how humans acquire language from infancy through adulthood: from babbling to complex grammar, and the theories that explain it all.

AP Psychology

What Is Language?

Language is a structured system of symbols and rules used to communicate meaning. It allows humans to convey abstract ideas, share knowledge, and form social bonds. Language is uniquely human in its generativity: the ability to produce an infinite number of sentences from a finite set of rules.

Building Blocks of Language

Phonemes
The smallest units of sound that distinguish meaning. English has about 44 phonemes (e.g., /b/ vs. /p/).
Morphemes
The smallest units of meaning. "Unhappiness" has 3 morphemes: un- + happy + -ness.
Syntax
The rules for combining words into grammatically correct sentences (word order matters).

The Language Hierarchy

Sentence Phrases / Words Syntax (Rules) Morphemes Semantics Pragmatics Phonemes

Stages of Language Development

0-4 mo
Cooing
Vowel-like sounds ("oooh," "aaah") expressing comfort
4-6 mo
Babbling
Consonant-vowel combos ("ba-ba," "da-da"); universal across cultures
~12 mo
One-Word (Holophrastic) Stage
Single words to convey entire meanings: "Milk!" = "I want milk"
~24 mo
Two-Word (Telegraphic) Stage
Two-word phrases: "Want cookie," "Daddy go"; mostly nouns and verbs
24+ mo
Multi-Word / Complex Speech
Rapid vocabulary growth; grammar rules emerge; sentences lengthen

The Critical Period Hypothesis

Proposed by Eric Lenneberg (1967), this hypothesis states that there is a biologically determined window for language acquisition, roughly from birth to puberty. After this period, acquiring a first language with native fluency becomes extremely difficult.

Age of First Exposure Ease of Acquisition 0 2 5 12 Adult Critical Period Ability to acquire language

Theories of Language Acquisition

Nativist (Chomsky)
Language is innate. We are born with a Language Acquisition Device (LAD) containing universal grammar.
Learning (Skinner)
Language is learned through operant conditioning: reinforcement, imitation, and shaping of verbal behavior.
Interactionist
Language emerges from both biology and social interaction. Children need innate ability + environmental input.

Nativist vs. Learning Theory

Nativist (Chomsky) Learning (Skinner)
Core Claim Language is innate Language is learned
Mechanism LAD / Universal Grammar Reinforcement + Imitation
Key Evidence Overgeneralization (e.g., "goed") Parents shape baby talk
Weakness Underestimates environment Can't explain novel sentences
Role of Biology Central Minimal

Linguistic Relativity

Benjamin Lee Whorf proposed that the language we speak shapes the way we think. This is known as the Sapir-Whorf hypothesis, which exists in two forms:

Strong Version
Language determines thought. Without a word for something, you cannot think about it. (Largely discredited.)
Weak Version
Language influences thought and perception. Supported: people with more color terms perceive color differences faster.

Brain Areas for Language

Broca's Area Wernicke's Area Arcuate Fasciculus Frontal Lobe Temporal Lobe
Broca's Area
Controls speech production. Damage causes Broca's aphasia: slow, effortful, agrammatic speech with intact comprehension.
Wernicke's Area
Controls speech comprehension. Damage causes Wernicke's aphasia: fluent but meaningless, "word salad" speech.

How to Identify Language Stages

1
Listen for sounds: Is the child producing vowel sounds only (cooing) or consonant-vowel combos (babbling)?
2
Count the words: One-word utterances = holophrastic stage; two-word combos = telegraphic stage.
3
Check for grammar errors: Overgeneralization (e.g., "I goed") signals the child is learning rules, not just imitating.
4
Match to theory: Does the example best support nativist, learning, or interactionist explanations?

Example: Identifying Stages

1
How many words? One word: "Dah."
2
What does it convey? A whole thought packed into a single word.
3
Stage: This is the holophrastic (one-word) stage, typically around 12 months.

Example: Overgeneralization

This error is called overgeneralization (or overregularization). The child has learned the rule "add -ed for past tense" and applies it even to irregular verbs.

Why It Matters
The child never heard an adult say "goed." This proves the child is generating language from internalized rules, not just imitating.
Theory Support
Strongly supports Chomsky's nativist theory: children possess innate grammar rules. Challenges Skinner's pure imitation model.

Example: Aphasia Types

1
Comprehension intact? Yes: the patient understands others.
2
Production impaired? Yes: speech is slow, effortful, and missing function words.
3
Diagnosis: Broca's aphasia: damage to the left frontal lobe's Broca's area.

Common Mistakes

✕ Confusing Phonemes and Morphemes
Phonemes are sounds (no meaning alone); morphemes are the smallest units of meaning. "Cat" has 3 phonemes but 1 morpheme.
✕ Swapping Broca's and Wernicke's
Broca's = production problems (non-fluent). Wernicke's = comprehension problems (fluent nonsense). Use the B/W mnemonic.
✕ Thinking Babbling = Words
Babbling is pre-linguistic: it contains sounds but no consistent meaning. The one-word stage begins when sounds gain meaning.

Summary of Key Concepts

Concept Definition Example
Phoneme Smallest unit of sound /b/ in "bat"
Morpheme Smallest unit of meaning "un-" in "undo"
Syntax Grammar rules for word order "The dog bit the man"
Semantics Meaning of words/sentences "Bark" (tree vs. dog)
Pragmatics Language use in context Sarcasm, politeness
LAD Chomsky's innate language device Universal grammar
Critical Period Window for language acquisition Birth to puberty

Question 1 of 5

A child says "mouses" instead of "mice." This error best supports which theory of language development?

Question 2 of 5

A patient produces fluent but meaningless speech and cannot comprehend spoken language. Which brain area is most likely damaged?

Question 3 of 5

A 22-month-old child says "Daddy go" and "want milk." Which stage of language development is this child in?

Question 4 of 5

The Sapir-Whorf hypothesis in its weak form suggests that:

Question 5 of 5

Which of the following is the best evidence for a critical period in language development?