Average duration of declaration (2023)

Expression Average Duration

Kinderlanguage developmentfollow a sequential order. This is true of developing expressive language skills, and as they mature, the length of their speeches increases (see alsoExtension of utterances with "E"). Consequently, we can relate the length of a sentence to the age of the child. Therefore, we can say that at the age of 20 to 30 months two statements are normally madeWordslong, at 28-42 months they have up to four words, at 34-48 months they have up to six words and from 48 months they have more than six words. Therefore, it should be possible to measure the typical duration of a child's speeches and determine whether or not it is appropriate for her age.

Well, the basic element of language is themorpheme[ie H. the smallest element in a language that can produce a difference in meaning, e.g. in the worddisinterested,dis-is a prefix-Interest-is a root and-edis a suffix: they are all morphemes] and not the word. Therefore, it is more revealing to determine the length of a child's utterances in terms of morphemes rather than words. The developing morphological abilities of the child are taken into account, as well as their own.syntactic skills. Of course, it is not enough to observe a single utterance, since the duration of utterances varies greatly. If I ask 'Where do you live?', you can simply say 'Hull' or 'In Hull' or 'I live in Hull' and so on. Therefore, it is necessary to examine several sentences and then calculate the average sentence length by counting the number of individual morphemes in each sentence. We will now provide a limited example of how to compute Average Expression Length (MLU).

Suppose we listen to a 48-month-old child make the following statements.

go home now

i live in billingham

mom kissed my dad

I like your dogs

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We can calculate the MLU as follows. We take each statement in turn and count the number of morphemes in the statements. Therefore, we would analyze the statements as follows.

So there are 17 morphemes in all. Now, to find the average sentence length, we take the total number of morphemes (17) and divide it by the total number of sentences (4). Therefore, the average length of the expressions is 17/4 = 4.25.

What we must do now is determine the age at which most children would exhibit an average speech duration equal to that attained by our particular child. This is known as theappropriate age. To do this, we read the age equivalent from Table 1. From the table, we see that an MLU of 4.25 is between 4.09 and 4.40. From this we can conclude that a child between the ages of 45 and 48 months would be expected to have an MLU of 4.25. Knowing that our particular son is 48 months old, the average length of the child's speeches seems appropriate for her age. This suggests, then, that this child's expressive language skills are developing in a typical way.

Table 1: Mean length of expressions (MLU) by age[Quelle: Miller (1981)]

It is worth making a final note about calculating an MLU. Whereas analyzing four utterances is better than analyzing only one (we would have an MLU of 3.00 if we analyzed only the child's first utterance).go home now), four statements are still not enough to achieve anything close to reasonable precision. Ideally, no fewer than 100 statements should be analysed. The more expressions that can be analyzed, the more accurate the result will be (Miller & Chapman, 1981; Bishop & Adams, 1990). While an MLU is useful as an indicator of expression language development, it should not be used as the sole measure of expression language capability. Garton and Pratt (1998) state that there is a positive correlation between EME and chronological age. However, they caution that the correlation is weak. Therefore, an MLU is at best a useful guide, as it is not robust enough to make detailed diagnostic measurements. For example, it is not always easy to decide what constitutes an utterance in a child's speech. It can also be difficult to determine what counts as a morpheme. For example, if the past simple of irregular verbs (p.corner,they brought,I went) are counted as a morpheme, while regular verbs (eg.mounted,reproduced,pushed) are counted as two? There is no doubt that the regular forms of the simple past tense consist of two morphemes, and we know that the child's ability to sign this past tense occurs early in morpheme acquisition (see Table 2).

Table 2. The order of acquisition of English morphemes[Source: Brown (1973) and Miller (1981)]

If our focus is on the child's growing ability to signal meaning, the irregular past tense can be considered on the same basis, that is, they also signal the meaning of the past tense. The fact that the irregular past tenses in English are not structurally composed of two easily identifiable elements is simply an artifact of the English language. However, it is questionable whether the child understands the irregular past tenses as separate units. From this perspective, they would be seen as built from a single morpheme: a unit of meaning, a morpheme.

Difficulties like those described above often result in different analysts calculating slightly different MLUs for the same returns. Because of this, it is common to specify the protocol to follow when calculating an MLU. Others may legitimately argue about the decision-making process, but at least one protocol provides a basic basis for calculating MLUs. Figure 1 shows a very typical protocol.

Figure 1. Protocol to calculate the average length of a statement[Quelle: Johnson (2005)]

Bishop, DVM & Adams, C. (1990) "A Prospective Study of the Relationship Between Specific Language Impairment, Phonological Disorders, and Reading Delay"Journal of Child Psychology and Psychiatry31, 1027–1050.

Brown, R. (1973)a first languageLondon: Allen and Unwin.

Garton, A. F. y Pratt, C. (1998)Learning to read and write (2nd ed.)Oxford: Blackwell.

Johnson, BW (2005)Mean Expression Length (MLU)[WWW] http://www.clas.ufl.edu/users/bwjohn/4004/Materials/MLU.htm Accessed 4/3/2009.

Miller, J. F. (1981) 'Deriving the procedure for language' in Miller, J. F. (Hrsg.)Assessment of language production in children.Londres: Eduard Arnold.

Miller, JF and Chapman, RS (1981) "The relationship between age and the average length of expressions in morphemes"Journal of Speech and Hearing Research24, 2, 154-161.