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How to Increase Mean Length of Utterance (MLU)


Did you know that when we talk about increasing a student’s sentence length, this is sometimes referred to as the MLU, or the mean length of utterance? We’re giving you some easy tips on how to increase mean length of utterance, or sentence length. 

I work with a lot of students. Some are speaking, some are non-speaking. And I always get these questions from parents: “How do I get my child to talk?” “How do I get my child to talk more?” It’s all about increasing the mean length of utterance. Whether we’re in a very preferred, relaxing spot or just in the natural environment, we want to be trying to model a lot of really natural language.

When a child first starts to talk, they usually have a mean length utterance of zero or one. They speak in one-word phrases. Some other students talk right away in longer phrases. Some of those students learn in what they call a gestalt learning process of language, which really means that they’re learning chunks of language at once. But let’s chat about those students who are talking in those one-word phrases. How do we get them to increase their vocabulary? 

Activities to Increase Mean Length of Utterance

The very first thing we want to do is make sure we’re teaching a lot of vocabulary. They should be learning 200, 300, or 400, verbs, nouns, etc before we start adding in language. Then one way to increase the mean length of utterance is by modeling all the time. I call it one-upping. One-upping means that if they say a word, we give them back two words. So if they say ball, we say yellow ball. If they’re requesting a cookie, we say big cookie. So we’re always giving them that extra word. 

We can also use visuals. So if we’re trying to prompt a student to say “the big brown bear is jumping at the park,” we could draw out some lines for them to indicate “bear, jumping, park.” Or we can use blocks or some other visuals so that they know they’ve got to start saying longer and longer phrases. 

We also are able to teach children longer phrases by teaching attributes. You can say things like, “what color is that?” as you hold up a green spoon. They say, “it’s green.” Then you say, “what is it?” They say, “spoon.” Then you can put the two together. “Let’s say green spoon.” Then if you have more than one item, you can say “how many?” We’ve got two green spoons. Try to use items that are really motivating for students.

How to Increase Mean Length of Utterance with Labeling

This is really about labeling for those students who learn in one or two-word phrases. So in the natural environment we’re constantly modeling more and more language, we’re doing that one-upping. But sometimes we really do need to teach it in a targeted way. If you’re a Bx Resource Pro Member, you can download a data sheet we created just for increasing MLU! We have a podcast episode all about data collection you should listen to as well.

You can teach labeling for quantity, size, color, noun, etc. So for example we might say “what is it?” while holding up a spoon. They say “spoon,” and then we ask what color it is. “Green spoon.” Then you can expand further with the quantity, “two spoons.” And then combine color and quantity together, “two green spoons.” And then slowly increase more words from there. We can add in other adjectives like dirty plate, big bumpy red ball, etc. Also prepositions like marker on plate or “who’s marker?” “Peppa’s marker.”

How to Fill in a Data Sheet to Increase MLU

So how would we mark it on our data sheet? We start with a baseline just to see where they’re at in terms of their mean length of utterance. I would hold something up and say, “what is it?” If they’re not giving me anything, or they’re giving me a one-word phrase, I’m going to mark that as one-word phrase. After that baseline, then I can go into the data sheet and write down the teaching steps. The first step is to combine two things, like color. Let’s stick with the example of the green spoon. I say, “what is this?” They say, spoon. Great. “What color is it?” It’s green. “Right, say the whole thing.” 

If they don’t give me anything, they say just spoon, or they say green, I mark the data sheet as a no. But then I can do a transfer trial. I might go on to something else and then come back and present a blue plate. “What is it?” They say plate. “What color is it?” Blue. “You got it, say the whole thing. Let’s put them together.” Blue plate. If I had to prompt it, I mark it as another no and go back to the transfer trial. 

I’ll do 10 trials for day 1 and then graph the percentage of how many yeses they get. The next day, I do teaching step number one again. They might get 60% yeses on the second day, maybe 90% on the third day, and 100% on the 4th. My teaching is working. Once I have enough data points I can connect the dots on the graph, mark a change in condition, and move on to teaching step number two. That’s how you would graph a teaching program for increasing the mean length of utterance.


Today we discussed how to increase mean length of utterance in students who are only speaking in one-word phrases or two-word phrases. Sometimes you have to put together a formal program and other times you can just really model it in the natural environment and do what I call one-upping. That means if a student gives you one word, we give them two words. If they give you three words, we give them four words. 

And make sure you model back to students constantly without that demand that they need to respond. We have another video blog on tips for increasing language in kids using books you can check out for even more information.

Get your free transfer trial visual to help you transfer the mean length of utterance skills to learners.

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