Introduction:

Calculating the Mean Length of Utterance (MLU) is an essential technique used to evaluate language development in children. The MLU provides insight into their syntactic and morphological abilities, giving parents, teachers, and speech therapists a valuable tool for understanding speech and identifying any potential delays. This article will walk you through the process of calculating MLU and provide tips on interpreting the data.

Step 1: Gather a sample of the child’s spontaneous speech

Observe the child interacting in their natural environment and record their chosen words during a conversation or play. Aim for at least 50-100 utterances to attain a reliable sample size.

Step 2: Transcribe the recorded data

Transcribe the recorded speech, writing down each word and separating them by spaces. Ensure accuracy by verifying your transcription with the recording.

Step 3: Divide the speech into utterances

Identify individual utterances by noting each time the child begins and ends an expression. This often coincides with pauses or clear breaks in thought. Mark each utterance separately using brackets or highlight different colors.

Step 4: Count morphemes per utterance

A morpheme is the smallest unit in language that holds meaning. Count both free morphemes (independent words like “dog” or “run”) and bound morphemes (affixes added to words such as “s” in “dogs” or “ing” in “running”). Keep a tally of the total number of morphemes for each utterance.

Important note: Some words may appear as single units but contain multiple morphemes (e.g., “butterfly” has two morphemes – “butter” and “fly”).

Step 5: Calculate MLU

To calculate MLU, divide the total number of morphemes by the total number of utterances:

MLU = Total Morphemes / Total Utterances

For example, if a child uses 200 morphemes in 50 utterances, the MLU would be 200/50 = 4.00.

Interpreting MLU Results:

MLU is widely used for assessing language acquisition in children aged 2-5 years. The developmental norms for MLU as established by Roger Brown are:

– 2 years old: MLU of 1.75-2.25

– 3 years old: MLU of 2.25-2.75

– 4 years old: MLU of 3.50-4.00

– 5 years old: MLU of 4.00-4.50

A child’s MLU should correlate with their age-appropriate norms to demonstrate typical language development. If the child’s MLU is significantly lower than expected, it may indicate speech or language delays, warranting further evaluation by a speech-language pathologist.

Conclusion:

Calculating MLU is a crucial tool in monitoring language development in young children, and understanding this comprehensive process can empower parents and educators to support their child’s linguistic growth effectively. Remember to consult a speech-language pathologist if concerns arise during your observations, and use the provided guidelines to make informed decisions for intervention and support strategies.