Morphology is the aspect of language concerned with the rules governing change in word
meaning. Morphological development is analyzed by computing a child’s Mean Length
of Utterance (MLU). Usually, a sample of 50 to 100 utterances is analyzed to draw
conclusions about the child’s overall production. Each word a child produces is broken
down into morphemes. A morpheme is the smallest, indivisible unit of meaning. For
example, the word “walk” is one morpheme, while “walked” is two morphemes: “Walk”
carries its own meaning and “ed” signifies past tense. Young children often combine
words to convey one meaning or idea. Consequently, words such as “gonna” count as
one morpheme. As adults, we understand that “gonna” really consists of both “going”
and “to”, each having meaning. After counting the morphemes for each of the child’s
utterances, they are totaled and divided by the total number of utterances. The formula is
as follows:
MLU= Total number of morphemes
Total number of utterances
A child’s MLU typically corresponds closely to their age. Roger Brown described five stages of language development based on MLU.
The following table outlines typical MLU development:
| Stage | MLU | Approximate Age (In Months) |
| I | 1.0-2.0 | 12-26 |
| II | 2.0-2.5 | 27-30 |
| III | 2.5-3.0 | 31-34 |
| IV | 3.0-3.75 | 35-40 |
| V | 3.75-4.5 | 41-46 |
| V+ | 4.5+ | 47+ |
Morphological acquisition is best outlined by Brown’s Fourteen Grammatical Morphemes.
The chart below details at what age each morpheme typically emerges.
| Morpheme | Example | Age of Mastery* (In Months) |
| Present Progressive – ing | Mommy driving | 19-28 |
| In | Ball in cup | 27-30 |
| On | Doggie on sofa | 27-33 |
| Regular plural -s | Kitties eat my ice cream. Forms: /s/, /z/ and /iz/ Cats, Dogs, Classes, Wishes | 27-33 |
| Irregular past | Came, fell, broke, sat, went | 25-46 |
| Possessive ‘s | Mommy’s balloon broke Forms: /s/, /s/ and /iz/ as in regular plural | 26-40 |
| Uncontractible copula (Verb to be as main verb) | He is. (Response to “Who is sick?) | 28-46 |
| Articles | I see a kitty. | 28-46 |
| Regular past –ed | Mommy pulled the wagon Forms: /d/, /t/, /Id/ Pulled, Walked, Glided | 26-48 |
| Regular third person -s | Kathy hits Forms: /s/, /z/, and /iz/ | 28-50 |
| Irregular third person | Does, has | 28-50 |
| Uncontractible auxiliary | He is. (Response to “Who is wearing your hat?”) | 29-48 |
| Contractible copula | Man’s big Man is big | 29-49 |
| Contractible auxiliary | Daddy’s eating Daddy is eating | 30-50 |
Sentence forms begin to develop as early as 12 months of age. Sentences can take on several different forms, including declarative, negative, interrogative, embedded and conjoined.
The following table details the development of each:
| Stage | Age (In Months) | Declarative | Negative | Interrogative | Embedding | Conjoining |
|---|---|---|---|---|---|---|
| Early I (MLU: 1-1.5) | 12-22 | Agent + Action; Action+ object | Single word-no, all gone, gone | Yes/no questions asked with rising intonation on a single word; what and where | Serial naming without and | |
| Late I (MLU: 1.5-2) | 22-26 | Subj. + Verb + Obj. | No and Not used interchangeably | What doing? | Prepositions in and on appear | And appears |
| Early II (MLU: 2-2.25) | 27-28 | Subj. + Copula + Compl. | Where going? | Gonna, wanna, gotta etc. appear | ||
| Late II (MLU:2.25-2.5) | 28-30 | Basic subject-verb-object used by most children | No, not, don’t, and can’t used interchangeably; negative element placed between subject and predicate. | Earliest inversion appears with copula in what/where + copula +subj | ||
| Early III (MLU:2.5-2.75) | 31-32 | Subj. + aux. verb + objet. Appears; auxiliary verb forms can, do have will and be appear | Auxiliary verbs do, can and will begin to appear in questions; inversion of subject and aux. verbs appears in yes/no questions | But, so, or and if appear | ||
| Late III (MLU:2.75-3) | 33-34 | Auxiliary verb appears with copula in subj. + aux. + copula + X | Won’t appears | Aux. Verbs do, can, and will appear in questions | ||
| Early IV (MLU:3-3.5) | 35-37 | Negative appears with auxiliary verbs | Inversion of auxiliary verb and subject in wh- questions | Object nounphrase complements appear with verbs such as think, guess and show; embedded wh questions | Clausal conjoining with and appears, because appears | |
| Late IV (MLU: 3-3.75 | 38-40 | Double auxiliary verbs appear in subj. + aux. aux.+ verb + X | Adds isn’t, aren’t doesn’t and didn’t | Inversion of copula and subject in yes/no questions; adds when and how | Infinitive phrases appear at the ends of sentences | |
| V (MLU:3.75-4.5) | 41-46 | Indirect object appears in subj. + aux. verb + ind. obj. + obj. | Adds wasn’t, wouldn’t, couldn’t, and shouldn’t | Some adult like tag questions appear | Relative Clauses appear | Clausal Conjoining with if appears; three clause declaratives appear |
| Post V (MLU:4.5+) | 47+ | Adds indefinite forms nobody, no one, none and nothing. Has difficulty with double negatives. | Questions other that one-word why questions appear. | Gerunds appear. Relative clauses attached to subject, embedding and conjoining appear within the same sentence above an MLU of 5.0 | Clausal conjoining with because appears with when, but and so beyond an MLU of 5.0 |
By age five, a child is able to use most of the major variations of the English language.
The order that these varieties are acquired indicates a pattern of cognitive, social and
learning growth. Language continues to develop into early adulthood to include more
sophisticated usage. For more on language development, consult the following
resources:
Adrian , A. (Ed.). (1995). Lingistics: an introduction to language and communication.
4th ed. Cambridge, MA: MIT Press.
Owens, R. (2001). Language development: an introduction. 5th ed. Needham Heights,
MA: Allyn and Bacon.