UNIT 3.5 · DEVELOPMENT AND LEARNING
Communication and Language Development — AP Psychology Notes
Review phonemes, morphemes, grammar, early language milestones, acquisition theories and brain networks for language.
What is Language?
Language is a shared, rule-governed system of arbitrary symbols used to communicate meaning through spoken, written, or signed words.
Unlike simple sounds or signals, language has three key properties: it uses arbitrary symbols (words don't inherently mean anything), follows systematic rules (grammar/syntax), and is generative (can produce infinite new sentences from finite building blocks).
Understanding how children acquire this complex system — moving from coos and babbles to fluent communication — reveals fundamental insights about human cognitive development.
Building Blocks of Language
Analyze different levels of language
- Phonemes
Contrastive sound units: /k/, /æ/, /t/ in “cat” - Morphemes
Meaningful units: “cat” and plural “-s” - Syntax
How words are combined into structured phrases - Semantics
Meaning expressed by words and sentences
Phonemes
Phonemes are the smallest distinctive sound units in a language that can change meaning.
Key Characteristics:
- Basic speech sounds that distinguish words from each other
- Phoneme inventories depend on dialect and analysis. English is often described as having about 44; Hawaiian is often described with a much smaller inventory. These are illustrative comparisons, not universal counts for every speaker.
- Changing one phoneme changes meaning: /b/at vs. /p/at
- Vary across languages — some languages use sounds others don't
- Do NOT carry meaning by themselves (just sounds)
Examples:
- The word "cat" has 3 phonemes: /k/ + /æ/ + /t/
- The word "ship" has 3 phonemes: /ʃ/ (sh) + /ɪ/ + /p/
- English “th” commonly represents two distinct sounds: /θ/ as in “thin” and /ð/ as in “this.” The written letters are not themselves a phoneme.
Morphemes
Morphemes are the smallest units of language that carry meaning — either as standalone words or meaningful word parts.
Two Types:
1. Free Morphemes
Can stand alone as words: "dog," "run," "happy," "the"
2. Bound Morphemes
Must attach to other morphemes; cannot stand alone
Examples of Bound Morphemes:
- Prefixes: "un-" in "unhappy," "re-" in "replay"
- Suffixes: "-ed" in "walked," "-s" in "cats," "-er" in "faster"
- Word analysis: "Unbreakable" has 3 morphemes: un- + break + -able
Semantics
Semantics refers to the meaning of words, phrases, and sentences — what the symbols represent.
What Semantics Covers:
- Literal definitions of words (dictionary meanings)
- Multiple meanings of the same word ("bank" = financial institution OR river edge)
- How word combinations create sentence meanings
- How context affects interpretation
- Relationships between concepts (synonyms, antonyms, categories)
Syntax and Grammar
Syntax concerns how words are organized into phrases and sentences. Grammar is broader and also includes morphology and other structural rules. A sentence can be syntactically well formed while expressing an unusual or false meaning.
Key Points:
- Determines proper word order and sentence structure
- Varies across languages (English: Subject-Verb-Object; Japanese: Subject-Object-Verb)
- Word order changes meaning even with same words
- Includes rules for tense, agreement, questions, negation
Example:
"The dog bit the man" vs. "The man bit the dog" — Same words, different syntax, completely different meaning!
Remember the Distinction
Phonemes = Sounds (no meaning)
Morphemes = Smallest meaningful units
Semantics = Meaning (what words/sentences represent)
Syntax = Structure/Rules (how words are arranged)
Three Key Properties of Language
1. Arbitrary Symbols
Words don't inherently mean anything — their meanings are socially agreed upon. The sound "dog" doesn't naturally represent a four-legged pet; English speakers simply agree that it does. Different languages use completely different sounds for the same concept.
2. Rule-Governed
Language follows consistent, learnable rules (grammar/syntax). These rules determine phoneme combinations, morpheme usage, and word order. Rules allow us to create and understand sentences we've never heard before.
3. Generative (Productive)
Language can produce an infinite number of novel sentences from a finite set of rules and building blocks. You can create and understand sentences that have never been spoken before — this is what separates human language from animal communication.
Stages of Language Development
Milestones describe broad patterns: Ages in the stage headings are illustrative ranges, not fixed deadlines. Language development varies across children and across spoken and signed modalities. Babbling, word combinations and increasingly complex grammar overlap rather than switching on at one exact age.
Language acquisition shows recurring patterns across many populations, with variation in timing, accessible input and spoken or signed modality. Stage labels summarize broad patterns, rather than universal deadlines.
Stage 1: Cooing (2-4 months)
Infants produce vowel-like sounds as they begin to experiment with their vocal apparatus.
- Sounds like "oooh" and "aaah"
- Early vocal play and practice
- Not yet language-specific
- Reflexive rather than intentional communication
Stage 2: Babbling (6-10 months)
Infants produce repetitive consonant-vowel combinations, practicing the phonemes they hear in their environment.
Characteristics:
- Repetitive sounds: "ba-ba-ba," "da-da-da," "ma-ma-ma"
- Begins to reflect the phonemes of the native language
- Universal at first, then becomes language-specific
- Important motor practice for speech production
- Deaf infants exposed to sign language "babble" with their hands
Important: Vocal and manual babbling patterns reflect both biological capacities and accessible input. Deaf infants may produce early vocalizations, but their later vocal and signed development depends on hearing access and language experience; not all follow an identical pattern.
Stage 3: One-Word/Holophrastic Stage (12-18 months)
Children use single words to express complete thoughts or ideas. One word carries the meaning of an entire sentence.
Characteristics:
- Single words represent whole ideas: "Milk!" can mean "I want milk" or "This is milk"
- Meaning depends heavily on context
- Rapid word learning often occurs in this period, with broad individual variation; a count such as 50 words is not a deadline every 18-month-old must meet.
- Shows understanding that symbols represent objects and ideas
- Uses concrete, familiar words (names, objects, actions)
Examples:
- "Mama" — could mean "I want mama" or "There's mama" or "Mama, come here"
- "Cookie" — might mean "I want a cookie" or "That's a cookie"
- "Up" — could mean "Pick me up"
Stage 4: Two-Word/Telegraphic Speech (18-24 months)
Children combine words into short phrases that resemble telegrams — containing only essential content words, omitting function words and grammatical markers.
Characteristics:
- Two-word combinations that convey meaning
- Omit articles, prepositions, helping verbs ("a," "the," "is," "are")
- Show early understanding of syntax and word order
- Demonstrate generativity — creating novel combinations
- Meaning is clear despite missing grammatical elements
Examples:
- "Want cookie" (instead of "I want a cookie")
- "Mommy go" (instead of "Mommy is going")
- "More milk" (instead of "I want more milk")
- "Daddy work" (instead of "Daddy went to work")
Beyond Telegraphic Speech (2+ years)
After age 2, children rapidly develop longer, more grammatically complex sentences.
- Add function words (articles, prepositions)
- Use correct tenses and grammatical markers
- Create increasingly complex sentences
- By age 6, most children speak fluently with adult-like grammar
Common Language Learning Patterns
Overextension
Using a word too broadly — applying it to more objects or situations than appropriate.
- Common during one-word stage
- Shows child is forming categories but boundaries aren't refined yet
- Reflects semantic development in progress
Example:
Calling all four-legged animals "doggy" — including cats, horses, and cows. The child extends the word "dog" to all similar-looking animals.
Underextension
Using a word too narrowly — applying it to fewer objects or situations than appropriate.
- Also common in early language development
- Child restricts word meaning too much
- Shows overly specific semantic understanding
Example:
Using "car" only for the family vehicle, not for other cars. Or calling only the family's specific dog "doggy" but not other dogs.
Overgeneralization (Overregularization)
Applying grammatical rules too broadly, including to irregular exceptions. This actually demonstrates that children are learning rules, not just memorizing!
Why It Happens:
- Child learns regular grammatical rule (add "-ed" for past tense)
- Applies rule systematically to ALL verbs, including irregular ones
- Shows active rule learning, not passive imitation
- Eventually learns irregular exceptions through continued exposure
Examples:
- "I goed to the store" (instead of "went")
- "She runned fast" (instead of "ran")
- "Two foots" (instead of "feet")
- "Three mouses" (instead of "mice")
Theories of Language Acquisition
Behaviorist Theory (B.F. Skinner)
Language is learned through operant conditioning — imitation, reinforcement, and shaping.
Core Ideas:
- Imitation: Children copy sounds and words they hear from adults
- Reinforcement: Correct language is rewarded (praise, getting needs met)
- Shaping: Adults gradually reinforce closer approximations to correct speech
- Association: Words paired with objects through repeated exposure
Criticisms:
- Cannot explain how children create novel sentences they've never heard
- Doesn't account for overgeneralization errors (children say "goed" even though they never heard it)
- Children learn language too quickly for reinforcement alone to explain
- Parents don't consistently correct grammatical errors, yet children learn correct grammar
Nativist Theory (Noam Chomsky)
Humans are born with an innate biological capacity for language acquisition. We have a built-in "language acquisition device."
Key Concepts:
Language Acquisition Device (LAD)
The language acquisition device (LAD) is a theoretical proposal about an innate capacity for learning language, not a discovered brain organ or literal device.
Universal Grammar
Universal grammar is a theoretical account proposing biologically constrained properties of human language. What is innate and how language is learned remain debated; infants are not born consciously knowing the grammar of every language.
Poverty of the Stimulus
Children learn complex grammar rules despite limited, imperfect input. The language they hear is "impoverished," yet they master rules — this suggests innate knowledge.
Evidence Supporting Nativism:
- Universal language milestones across all cultures
- Children can develop homesign systems and communities can develop new signed languages. These findings do not mean a child needs no accessible language input or social interaction for full language development.
- Critical/sensitive period for language acquisition
- Language learning is rapid and follows predictable patterns
- Children generate grammatical sentences they've never heard
Interactionist/Social Interactionist Theory
Language develops through the interaction of biological predispositions and social/environmental experiences. Combines elements of both behaviorist and nativist views.
Key Ideas:
- Children are biologically prepared to learn language (innate capacity)
- BUT social interaction and environmental input are essential for development
- Joint attention, gestures (pointing), and caregiver responsiveness scaffold learning
- Cultural tools and social context shape specific language development
- Interactionist accounts consider biological capacities together with social input and active learning. They are a broad family of explanations, not a single theory proved to explain every aspect of language.
Brain Areas for Language
Use the mnemonic carefully: “Broca = broken speech” and “Wernicke = fluent but impaired meaning/comprehension” summarize common patterns. Aphasia can affect speaking, understanding, reading and writing in different combinations; a shorthand is not a complete diagnosis.
Broca's Area
Located in the frontal lobe (usually left hemisphere)
Function:
Supports aspects of language production, planning and grammatical processing as part of a wider network; speech is not controlled by one isolated muscle-command center.
Damage causes Broca's Aphasia:
- Difficulty speaking
- Slow, effortful, telegraphic speech
- Comprehension can be relatively stronger than speech output, but complex grammar and other language tasks may also be affected.
- Know what to say but can't say it
Wernicke's Area
Located in the temporal lobe (usually left hemisphere)
Function:
Posterior temporal networks contribute to language comprehension and meaning, alongside other interconnected regions; comprehension is not located in one isolated box.
Damage causes Wernicke's Aphasia:
- Fluent but meaningless speech
- Poor comprehension
- Nonsensical word combinations
- Can speak easily but it doesn't make sense
Memory Trick
Broca = Broken speech (can't produce language)
Wernicke = Word salad (can't understand language, speak nonsense)
Critical/Sensitive Period for Language
The Critical Period Hypothesis
There is an optimal window for language acquisition (roughly birth through puberty) when the brain is especially receptive to linguistic input. After this period, language learning becomes significantly more difficult.
Evidence:
- Second language acquisition: Children learn second languages more easily and achieve native-like fluency
- Case studies: Children deprived of language exposure early (like Genie) never fully acquire normal language
- Deaf children: If not exposed to sign language early, have difficulty later
- Brain plasticity: Language areas of the brain are most flexible in childhood
Important Note:
Age-related sensitivity differs across pronunciation, grammar and other skills, and first-language access differs from later second-language study. Early access to a rich spoken or signed language matters. Later learning remains possible, with considerable variation; there is no single universal cutoff that makes all language learning impossible after puberty.
AP Exam Strategy
Multiple Choice Tips
- Master vocabulary: Phonemes vs. morphemes, semantics vs. syntax, overextension vs. overgeneralization
- Know the stages IN ORDER: Cooing → Babbling → One-word → Two-word/Telegraphic
- Identify stages from examples: "Want cookie" = telegraphic; "goed" = overgeneralization
- Compare theories: Skinner (reinforcement) vs. Chomsky (LAD, universal grammar) vs. Interactionist (both)
- Brain areas: Broca's = production, Wernicke's = comprehension
- Understand language properties: Arbitrary symbols, rule-governed, generative
Free Response Question (FRQ) Tips
- Define terms precisely: Don't confuse phonemes with morphemes or semantics with syntax
- Use specific examples: For overgeneralization, give "goed" not just "grammar errors"
- Apply theories to scenarios: Explain how Chomsky would explain a child saying novel sentences
- Link brain damage to symptoms: Broca's damage → can't produce speech but understands
- Explain developmental patterns: Why telegraphic speech omits function words but preserves meaning
- Connect concepts: How LAD relates to critical period and universal grammar
Quick Review Summary
The Big Picture
Language uses structured, productive systems of symbols in spoken, written and signed modalities. Phonemes are contrastive sound units; morphemes carry meaning; syntax concerns phrase and sentence structure; semantics concerns meaning. Grammar is broader than syntax alone. Broad early patterns include cooing, babbling, single words and word combinations, with variable timing. Overextension broadens a label too far, underextension restricts it, and overregularization applies a rule to an exception, as in “goed.” Behaviorist, nativist and interactionist accounts emphasize different learning processes. LAD and universal grammar are theoretical constructs rather than a discovered brain device. Broca-associated and posterior temporal regions contribute to wider language networks; aphasia patterns vary across production, comprehension, reading and writing. Early accessible language matters, while later learning remains possible and age effects differ across skills.
Essential Concepts
- Language
- Phonemes
- Morphemes (free & bound)
- Semantics
- Syntax and grammar
- Arbitrary symbols
- Rule-governed
- Generative/Productive
- Cooing
- Babbling
- One-word/Holophrastic stage
- Telegraphic speech
- Overextension
- Underextension
- Overgeneralization
- Behaviorist theory (Skinner)
- Nativist theory (Chomsky)
- Language Acquisition Device (LAD)
- Universal grammar
- Poverty of the stimulus
- Interactionist theory
- Broca's area
- Wernicke's area
- Broca's aphasia
- Wernicke's aphasia
- Critical/Sensitive period
Quick FAQs
Is a phoneme the same as a letter?
No. A phoneme is a contrastive sound unit. A written letter can represent different sounds, and multiple letters can represent one sound.
Is the language acquisition device a known brain organ?
No. The LAD is a theoretical account of language-learning capacity, not a discovered anatomical device. Language involves distributed brain networks and experience.