What is intelligibility?

Intelligibility refers to how much of what a child says we understand. It is common for children to make errors with the sounds they produce. As children get older, they should start to say sounds correctly and we understand more of what they say. By the time a child is 5 years old, we should be able to understand 100% of what they say and they should consistently produce most sounds correctly.

There are various ways to think about intelligibility. We understand more about what children say with context. For example, if your child is playing with dolls, they are likely talking about dolls, so it is easier to guess at what they say even if there are errors. If we don’t have context, it is usually harder to understand what a child is saying when they make sound errors.

It is also easier to understand what a child says when we know the child well. When someone knows the child well, they are called a “familiar listener.” Parents, siblings, and other caregivers are considered familiar listeners, because they spend a lot of time with the child. It is common for parents to understand their child better than people who spend less time with their child (e.g., “unfamiliar listeners”). If your child makes a lot of mistakes with their sounds, you may be able to understand them most of the time, but you might notice that less familiar or unfamiliar listeners, like your child’s teacher, your child’s friends, or other adults have a hard time understanding your child.

So how much of what your child says should you be able to understand?

Between 19 and 24 months, children should be 25-50% intelligible to an unfamiliar listener without context. That is, you should be able to understand 25-50% of what your child says.

Between 2 years and 3 years, children should be 50-75% intelligible to an unfamiliar listener without context.

Between 4 years and 5 years, children should be 75-90% intelligible to an unfamiliar listener without context.

And beyond 5 years old, children should be 90-100% intelligible to an unfamiliar listener without context.

If your child hasn’t met these intelligibility milestones, it’s a good idea to get a speech-language evaluation to see if speech-language therapy could help your child improve the way they produce sounds.

References:

Lanza, J. R., & Flahive, L. K. (2008). Guide to communication milestones: Concepts, feeding, morphology, literacy, mean length of utterance, phonological awareness, pragmatics, pronouns, questions, speech sound acquisition, vocabulary. LinguiSystems.