Mean length of utterance (or MLU) is a measure of linguistic productivity in children. It is traditionally calculated by collecting 100
utterance
In spoken language analysis, an utterance is a continuous piece of speech, often beginning and ending with a clear pause. In the case of oral languages, it is generally, but not always, bounded by silence. Utterances do not exist in written langu ...
s spoken by a child and dividing the number of
morpheme
A morpheme is the smallest meaningful Constituent (linguistics), constituent of a linguistic expression. The field of linguistics, linguistic study dedicated to morphemes is called morphology (linguistics), morphology.
In English, morphemes are ...
s by the number of utterances. A higher MLU is taken to indicate a higher level of language proficiency.
Mean length of utterance is a good marker of language impairment. It is the number of words or morphemes in each of their spontaneous utterances. It can be used to benchmark language acquisition and is used to compare language intervention outcomes in children with autism. In testing of children ages 3-9 with diagnoses of autism or autism spectrum disorders and nonverbal IQ scores below 85, results indicated that children with autism persistently scored below the unaffected group without significant improvement in scores concerning mean length of utterance. There may be variability in outcomes due to sampling differences.
A study by Bishop and Adams (1990) suggests that MLU at 4.5 is a good predictor of reading ability at age 8. Nonetheless MLU is considered controversial, and should not be used as the only diagnostic measure of language proficiency in children.
See also
*
Language acquisition
Language acquisition is the process by which humans acquire the capacity to perceive and comprehend language (in other words, gain the ability to be aware of language and to understand it), as well as to produce and use words and sentences to ...
*
Language development
Language development in humans is a process starting early in life. Infants start without knowing a language, yet by 10 months, babies can distinguish speech sounds and engage in babbling. Some research has shown that the earliest learning begin ...
References
* Bishop, D. V. M., & Adams, C. (1990). A prospective study of the relationship between specific language impairment, phonological disorders and reading retardation. ''Journal of Child Psychology and Psychiatry,'' 31, 1027–1050.
External links
The Effect of Coffee Consumption on Adults’ Average MLU at the Breakfast Table A humorous article demonstrating some of the criticisms of MLU—namely that extra-linguistic factors can greatly affect MLU.
Reading (process)
Units of linguistic morphology
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