Speech Intelligibility
The term speech intelligibility is used to describe how well a child (or adult) can be understood by other people, how “intelligible” they are.
It has absolutely nothing to do with how smart (intelligent) a child is. The range goes from 0% (you don’t understand anything they say) up to 100% (you understand everything.)
Intelligibility norms, or the percentage of what a child says that you would expect to be able to understand increases throughout toddlerhood. More on intelligibility norms next.
Speech Intelligibility Norms
It is hard for others to understand my child, is this normal?
Before sharing intelligibility norms for toddlers, it’s important to know that we’d expect different people to understand your toddler different amounts.
It is normal for parents and close family members to understand your child better than anyone else-- you are the expert! Your brain learns to interpret the way that your child says certain things, like when your child says “tuti” for cookie or “baper” for diaper, or lately my 3 year old saying “Pinnie Woo” for Winnie the Pooh! Our parent brain understands them better than anyone else.
With that said, you want to know if how much you or others understand of your child is normal. This chart below should help. This chart shows how well a child should be understood by a particular age. It is separated into a Primary Caregiver column and an Others column. As you've already learned, parents will generally understand more than the grocery store clerk or an auntie that sees the child only once a month .
Speech Intelligibility Norms:
| Age | Intelligibility to Parents + Primary Caregivers | Intelligibility to Others |
|---|---|---|
| 18 months | 25% | 0-25% |
| 2 years (24 months) | 50-75% | 25-50% |
| 3 years | 75-100% | 50-75% |
| 4 years | 100% | 100% |
How is speech intelligibility measured?
Speech therapists will use a precise analysis to determine what percentage of a child’s speech is understood.
At home, you can get a pretty good idea of your child’s intelligibility by recording them talking for several minutes (it’s okay if you take a couple of videos). Once the videos have been recorded play them back. Create two columns on a sheet of paper, “Words I understood” versus “Words I didn’t understand.” Use tally marks to score each category as you listen back.
Once you have completed your tallying count up each side. Then you will want to divide:
(# Words Understood / (#Words Understood + #Words Not Understood)) x100 = % Intelligibility
So for example, if you understood 55 words and did not understand 45 words you would divide (55/100)x100 = 55% Speech Intelligibility.
Why are speech intelligibility norms important?
Speech intelligibility is a good indicator of a child’s overall speech development. If you understand less than the expected percentage for a child’s age it is indicative that a child is having difficulty in one or more areas of speech development.
So if your child is hard to understand, a speech and language evaluation with a licensed speech therapist is a recommended next step.
Speech therapists can help identify which area of speech is impacting intelligibility and determine if a speech sound disorder is present. Plus speech language pathologists (another name for a speech therapist) know tons of research backed techniques to support your child’s speech development.
Speech therapists will often use speech intelligibility as a way to measure progress across speech therapy sessions as well. In speech therapy the goal of all the activities and exercises is to help your child be more easily understood by others after all.
What affects speech intelligibility?
There are 3 main areas of speech that impact speech intelligibility. As toddlers develop their skills in each area of speech, their intelligibility will naturally improve. However, if a child faces difficulties developing one or more areas of speech, their speech intelligibility would begin to fall behind the age expected norms.
1. Articulation - Articulation includes the individual sounds a child can say. Articulation difficulties can make it harder to understand a child because many words may be pronounced the same way. When a child is unable to pronounce a particular sound they will either:
leave that sound out of a word completely (ex. If a child can’t pronounce “t” yet, then Bat would sound like “Ba”).
Or substitute another sound (ex. If a child can’t pronounce “t” yet, then Bat would sound like “Bap”)
2. Phonology - Phonology refers to the ways that people combine sounds together. Developing phonology skills allows children to say longer words and words with different combinations of vowels and consonants. If a child struggles developing phonology skills they may not be able to pronounce consonant sounds at the ends of words, so words like Cat, Milk, and Plate would sound like “Ca” “Mi” and “Pay.”
3. Motor Speech Skills - Motor speech skills include the way a child coordinates all the precise and rapid movements of their mouth to make specific sounds and say words. When a child has difficulty developing their motor speech skills parents can often understand them equally as well as less familiar adults because their errors are different every time. Speech therapy is particularly beneficial for these children.
What should I do if I’m worried about my child’s speech sounds?
If you don’t feel that your child has the sounds they should for their age, or others (or even you) can’t understand them as much as we would expect, it is time to ask for a little extra help by talking to your doctor or contacting your state/county’s Early Intervention service.
The first thing your doctor may do is to ask for a hearing test. Even if a baby passes the newborn hospital hearing screening, they may have had ear infections or other ear issues that you didn’t know about that have made it harder for them to hear each sound correctly and clearly. It is important to rule out any hearing difficulties is a speech sound disorder is suspected.
In addition, you would likely benefit from some extra help from a speech-language pathologist. A speech-language pathologist will be able to look at your child’s specific situation in depth and help you really determine if they fall in the expected range, and/or make a plan to help them improve their speech sounds and their intelligibility.
Learning a new speech sound, let alone all 44 of them, is no easy feat. It takes time and practice to master the coordination of each movement needed to make a sound. This is why we expect easier sounds to be produced by younger children and save the harder sound production for older kids. Keeping these charts in mind for what we would generally expect may guide you on what sounds to really watch for and be mindful of when talking to and playing with your child.
Get a free copy of our intelligibility guide for toddlers ↓
Here are some other questions parents often ask about speech intelligibility:
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Parents should be able to understand their 2 year old about 50-75% of the time.
Adults who spend less time with a child will understand them less.
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A 2.5 year old should be speaking clearly most of the time. You can usually understand what a 30 month old is saying about 75% of the time.
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Parents usually begin understanding about half of what their children are saying by the time they are 2 years old (24 months). You can expect to understand what your child is saying about 100% of the time when they are between 3-4 years old.
At 3-4 years old, it’s important to note they will still mispronounce some words, but it will be really easy to understand what they are trying to say.
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Written By:
Stephanie Keffer, MS CCC-SLP
Stephanie Burgener-Vader MA CCC-SLP
© 2020-2023. Stephanie Keffer, MS CCC-SLP. All Rights Reserved.
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