How to Calculate Mean Length of Utterance (MLU) in English

How to Calculate Mean Length of Utterance (MLU) in English: A Definitive Guide

Have you ever wondered how linguists measure the language development of children?

One commonly used method is calculating the Mean Length of Utterance (MLU). MLU is a quantitative measure that provides insights into a child's language abilities and helps researchers gauge their progress. In this article, we will delve into the details of calculating MLU in English, addressing some frequently asked questions along the way.

What is the Mean Length of Utterance (MLU)?

MLU is a measure of linguistic productivity used to evaluate a person's language development. It is typically calculated by determining the average number of morphemes (the smallest meaningful units of language, such as words or prefixes) in each utterance.

How can I calculate the MLU?

To calculate MLU, count the total number of morphemes in a speech sample and divide it by the number of utterances. The resulting quotient represents the average length of each utterance.

What constitutes an utterance?

An utterance refers to a complete, meaningful statement or remark, which includes one or more words. It can be a full sentence, a phrase, or even a single word.

Can you provide an example of calculating MLU?

Certainly. Let's consider the following speech sample: Utterance 1: "I see a cat" (4 morphemes) Utterance 2: "Mommy, look!" (2 morphemes)

Utterance 3: "Where is my toy?

" (4 morphemes) Utterance 4: "Daddy is at work" (4 morphemes) To calculate MLU, sum up the number of morphemes (4+2+4+4=14) and divide it by the total number of utterances (4). In this case, the MLU would be 14/4=3.5.

Are there any additional considerations when calculating MLU?

Yes, there are a few important factors to keep in mind. First, when calculating MLU, only consider the child's actual words or morphemes—not interjections, fillers, or non-linguistic sounds. Second, compound words, such as "bathroom" or "playground," should be counted as a single morpheme. Lastly, contractions like "can't" or "doesn't" should be treated as two morphemes.

Is there a specific age range where MLU is commonly used?

Yes, MLU is predominantly used to analyze the language development of children between the ages of 2 and 5. During this period, children experience significant linguistic growth, making MLU a valuable tool for evaluating their language skills.

How can MLU be useful for language researchers?

MLU allows researchers to compare language development across different individuals or groups. It can indicate whether a child's language skills are within the typical range for their age, or if they require further assessment and intervention.

Are there any limitations to using MLU?

While MLU provides valuable insights, it should not be the sole basis for evaluating language development. Factors such as vocabulary size, syntactic structure, and pragmatics also play important roles in assessing language abilities. Therefore, MLU should be used in conjunction with other measures for a comprehensive understanding. In conclusion, MLU is a useful measure in evaluating language development, allowing researchers to quantify a person's linguistic productivity. By calculating the average number of morphemes per utterance, MLU provides valuable insights into a child's language skills. However, it is crucial to consider other factors and use MLU in conjunction with other measures for a well-rounded assessment of language abilities.