1.7 Communication and Language Development: Typical and Atypical Patterns

Prelinguistic Foundations and the Typical Sequence

Communication development begins long before the first word, and the prelinguistic milestones are the earliest reliable predictors of later language and social outcomes. A special educator asked to judge whether a referral is warranted needs the sequence, not just the endpoints.

Prelinguistic Milestones (Birth to 12 Months)

• Birth to 3 months: startles and quiets to voice; differentiated crying; cooing.
• 4 to 6 months: vocal play and marginal babbling; localizes to sound; laughs.
• 6 to 9 months: canonical (reduplicated) babbling ("bababa"). Absence of canonical babbling by about 10 months is one of the strongest early red flags for hearing loss or a communication disorder.
• 9 to 12 months: joint attention — coordinating attention with an adult toward a third object; protodeclarative pointing (pointing to share interest, not to request); gesture, wave, and give routines. Reduced joint attention and absent protodeclarative pointing are core early indicators for autism spectrum disorder.

Expressive Milestones

Intelligibility Benchmarks

Intelligibility to an unfamiliar listener is the practical screening measure, because familiar caregivers over-interpret:

• Age 2: approximately 50 percent intelligible
• Age 3: approximately 75 percent intelligible
• Age 4 and beyond: approximately 100 percent intelligible, even if some sounds are still in error

A four-year-old whom strangers frequently cannot understand warrants a speech-language referral regardless of how well the family understands them.

The Five Components of Language

Every language disorder is described by which of these rule systems is affected:

• Phonology — the sound system and the rules for combining phonemes.
• Morphology — the smallest units of meaning: plural -s, past tense -ed, prefixes and suffixes.
• Syntax — word order and sentence structure.
• Semantics — word and sentence meaning, including word-finding and figurative language.
• Pragmatics — the social use of language: turn-taking, topic maintenance, register shifting, repairing a misunderstanding, and interpreting idiom, sarcasm, and indirect requests.

Phonology and morphology are the two components most often confused. "He tooked the ball" is a morphological error (overregularized past tense). "He took the ball" produced as "He tood the ball" is a phonological error.

Atypical Patterns, Developmental Language Disorder, and Difference Versus Disorder

Speech Disorders Versus Language Disorders

The distinction drives the service target, so the exam tests it repeatedly.

A useful screen: if you can transcribe what the student said but the message still does not work, the problem is language, not speech.

Developmental Language Disorder (DLD)

DLD is a persistent language impairment without an identifiable biomedical cause such as autism, hearing loss, or intellectual disability. It affects roughly 7 percent of children — considerably more common than autism — yet it is chronically under-identified because these students are neither disruptive nor unintelligible. Classroom markers include:

• Difficulty with grammatical morphology, especially verb tense marking, that persists past the primary grades
• Word-finding difficulty and reliance on vague placeholders ("the thing," "stuff," "you know")
• Poor narrative structure: events out of order, missing referents, listener left confused
• Reasonable decoding but weak reading comprehension from about third grade onward

Because of that last pattern, DLD is one of the most important explanations for the "good decoder, poor comprehender" profile, and a student who fails comprehension despite adequate word reading should be screened for oral language before more phonics is prescribed.

Language Difference Is Not a Disability

IDEA prohibits identifying a student whose difficulty is caused by limited English proficiency. Normal second-language acquisition produces phenomena that look disordered to an untrained observer:

• A silent period of weeks to months in which the learner is receptive but not productive
• Code-switching, which reflects competence in two systems rather than confusion
• Transfer errors from the first language's phonology or syntax
• Strong conversational fluency alongside weak academic language, since social language develops in roughly one to three years while academic language takes five to seven or more

The decision rule is straightforward: a true disorder is present in every language the student speaks. Establishing that requires assessment in the home language (or with a trained interpreter), comparison to true peers with a similar language and schooling history rather than to monolingual norms, and dynamic assessment using a test-teach-retest cycle. High modifiability — a big jump after brief teaching — indicates a learner who lacked exposure, not a learner with a disorder.

When to Refer

Refer for a speech-language evaluation when: no canonical babbling by 10 months; no words by 15 months; fewer than 50 words or no word combinations at 24 months; intelligibility to unfamiliar listeners well under the age benchmark; sudden loss of previously acquired words at any age; stuttering that persists beyond six months, includes physical tension or blocks, or is accompanied by avoidance; or a persistent gap in following directions and narrative production that appears in the home language as well.