AP Psychology Unit 3: Communication and language development

What the exam asks

Concept application (Section I): Given a word or sentence, identify its phonemes or morphemes, or determine whether an error involves semantics or syntax.
Developmental tracking (Section I & II): Identify which stage of language development an infant or toddler is in based on a behavioral vignette, or explain how a specific grammatical error (overgeneralization) demonstrates cognitive rule-learning.
Research analysis (Section I sets, AAQ, EBQ): Operationalize language variables in developmental studies (e.g., counting the number of words per utterance) or apply linguistic concepts to support a claim about early cognitive development.

In psychology, language is defined by three core properties:

Shared and arbitrary symbols: Spoken sounds, written letters, and manual signs do not naturally resemble the things they represent (the word dog does not look or sound like a dog), yet speakers of a language agree on their meaning.
Rule-governed: Shared rules dictate how symbols are combined so others can understand them.
Generative (productive): A finite set of symbols and rules can be combined to create an infinite number of novel, meaningful messages.

Component	Definition	Example
Phoneme	The smallest distinctive unit of sound in a spoken language (or hand shape/movement in sign language).	The word chat has 3 phonemes: `/ch/`, `/a/`, `/t/`.
Morpheme	The smallest unit that carries meaning in a language. Includes root words, prefixes, and suffixes.	The word unbreakable has 3 morphemes: un- (not), break (root), and -able (capable of).
Grammar	The full system of rules (including both semantics and syntax) that enables communication.	All rules governing how English is structured and understood.
Semantics	The rules used to derive meaning from words and sentences.	Knowing that “A crash blossom is a headline” is about journalism, or adding -ed means the past.
Syntax	The rules for combining words into grammatically sensible word order in a sentence.	In English, adjectives usually precede nouns (white house), whereas in Spanish they follow (casa blanca).