Grammatical Development

Grammatical development describes how children acquire the rules that govern how words are combined into phrases, clauses, and sentences. This includes the acquisition of morphology (word structure — e.g. adding "-ed" for past tense) and syntax (sentence structure — e.g. word order, clause combining). Grammatical development is one of the richest areas for data analysis at A-Level.

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From One Word to Two Words

As discussed in the lesson on lexical development, children begin with single-word utterances (holophrases) around 12–18 months. The transition to two-word utterances typically occurs around 18–24 months and represents a fundamental milestone: for the first time, children are combining words according to rudimentary grammatical rules.

Two-Word Stage

At the two-word stage, children produce utterances that express basic semantic relationships:

Semantic Relationship	Example	Meaning
Agent + action	"Daddy kick"	Daddy is kicking
Action + object	"Hit ball"	(I am) hitting the ball
Agent + object	"Mummy shoe"	Mummy's shoe / Mummy (put on my) shoe
Entity + attribute	"Big dog"	The dog is big
Entity + location	"Teddy bed"	Teddy is on the bed
Possessor + possession	"My cup"	That is my cup
Recurrence	"More milk"	I want more milk
Negation	"No bed"	I don't want to go to bed

Key Definition: Two-word stage — the period (approximately 18–24 months) in which children begin combining two words to express basic semantic relationships. Despite the absence of grammatical markers (articles, prepositions, inflections), these utterances demonstrate an emerging understanding of word order and meaning.

Telegraphic Speech

Two-word and early multi-word utterances are often described as telegraphic speech because they contain only the essential content words (nouns, verbs, adjectives) and omit function words (articles, prepositions, auxiliary verbs, inflections) — much like the abbreviated language of a telegram.

Adult form	Telegraphic form
"I want more milk, please"	"More milk"
"Daddy is kicking the ball"	"Daddy kick ball"
"The cat is sitting on the mat"	"Cat sit mat"
"I don't want to go to bed"	"No go bed"

Pivot Grammar

Braine (1963) proposed the concept of pivot grammar to describe the structure of two-word utterances. He observed that children use certain words (pivot words) in a fixed position, combined with a range of other words (open words):

• Pivot words: A small set of frequently used words that always appear in the same position (e.g. "more", "no", "all gone")
• Open words: A larger set of words that can be combined with pivot words (e.g. "milk", "juice", "biscuit")
• Example: "more milk", "more juice", "more biscuit" — "more" is the pivot word, always in initial position

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Multi-Word Stage and Beyond

From approximately 2–3 years, children's utterances become increasingly longer and more complex, gradually incorporating grammatical markers.

Brown's Stages of Morphological Development

Roger Brown (1973) conducted a landmark longitudinal study of three children — Adam, Eve, and Sarah — and identified a consistent order in which English-speaking children acquire grammatical morphemes. Brown measured development using Mean Length of Utterance (MLU) — the average number of morphemes per utterance.

Key Definition: Mean Length of Utterance (MLU) — a measure of linguistic productivity calculated by dividing the total number of morphemes in a sample of a child's speech by the number of utterances. MLU increases as children develop grammatically. Brown (1973) used MLU to define five stages of grammatical development.

Brown's Stage	MLU	Age (approx.)	Key Features
I	1.0–2.0	12–26 months	Single words and two-word combinations; telegraphic speech
II	2.0–2.5	27–30 months	Grammatical morphemes begin to appear (e.g. -ing, plurals, in, on)
III	2.5–3.0	31–34 months	Simple sentence structures; use of questions and negatives
IV	3.0–3.75	35–40 months	Complex sentences with embedding; use of auxiliary verbs
V	3.75–4.5	41–46 months	Coordination and subordination; complex clause structures

Order of Morpheme Acquisition

Brown identified 14 grammatical morphemes that are acquired in a remarkably consistent order by English-speaking children:

Order	Morpheme	Example
1	Present progressive -ing	"Daddy running"
2	Preposition in	"In box"
3	Preposition on	"On table"
4	Regular plural -s	"Two dogs"
5	Irregular past tense	"went", "came"
6	Possessive 's	"Mummy's hat"
7	Uncontractible copula be	"He was good"
8	Articles a/the	"A dog", "the cat"
9	Regular past tense -ed	"I walked"
10	Third person regular -s	"He runs"
11	Third person irregular	"He does", "She has"
12	Uncontractible auxiliary be	"He was running"
13	Contractible copula be	"He's good"
14	Contractible auxiliary be	"He's running"

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Overgeneralisation (Virtuous Errors)

One of the most revealing features of children's grammatical development is overgeneralisation — the application of a grammatical rule to cases where it does not apply, producing forms that are not found in adult speech.