Early Morphological Development

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:

StageMLUApproximate Age
(In Months)
I1.0-2.012-26
II2.0-2.527-30
III2.5-3.031-34
IV3.0-3.7535-40
V3.75-4.541-46
V+4.5+47+
Source: Compiled form Brown (1973)

Morphological acquisition is best outlined by Brown’s Fourteen Grammatical Morphemes.
The chart below details at what age each morpheme typically emerges.

MorphemeExampleAge of Mastery*
(In Months)
Present Progressive – ingMommy driving19-28
InBall in cup27-30
OnDoggie on sofa27-33
Regular plural -sKitties eat my ice cream.
Forms: /s/, /z/ and /iz/
Cats, Dogs, Classes, Wishes
27-33
Irregular pastCame, fell, broke, sat, went25-46
Possessive ‘sMommy’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
ArticlesI see a kitty.28-46
Regular past –edMommy pulled the wagon
Forms: /d/, /t/, /Id/
Pulled, Walked, Glided
26-48
Regular third person -sKathy hits
Forms: /s/, /z/, and /iz/
28-50
Irregular third personDoes, has28-50
Uncontractible auxiliaryHe is.
(Response to “Who is
wearing your hat?”)
29-48
Contractible copulaMan’s big
Man is big
29-49
Contractible auxiliaryDaddy’s eating
Daddy is eating
30-50
*Used correctly 90% of the time in obligatory contexts. Adapted from Bellugi & Brown (1964); R. Brown (1973); and J. Miller (1981).

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:

StageAge
(In
Months)
DeclarativeNegativeInterrogativeEmbeddingConjoining
Early I
(MLU: 1-1.5)
12-22Agent + 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)
22-26Subj. +
Verb + Obj.
No and Not used
interchangeably
What doing?Prepositions
in and on
appear
And appears
Early II
(MLU: 2-2.25)
27-28Subj. +
Copula +
Compl.
Where going?Gonna,
wanna,
gotta etc.
appear
Late II
(MLU:2.25-2.5)
28-30Basic
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)
31-32Subj. + 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)
33-34Auxiliary
verb
appears
with copula
in subj. +
aux. +
copula + X
Won’t appearsAux. Verbs
do, can, and
will appear in
questions
Early IV
(MLU:3-3.5)
35-37Negative
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
38-40Double
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)
41-46Indirect
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.