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Snapshot: What is intelligibility?

Speech intelligibility refers to how many words can be correctly understood by a listener. For example, if someone says the phrase, “My name is John,” and a listener hears, “My name is Tom,” then the listener correctly understood 75% of the speech.

In a formal speech evaluation, the percentage of words understood will be calculated for a longer sample of speech, such as a three-minute description of someone’s typical day. The speech-language pathologist (SLP) would then conclude that the patient’s speech is, for example, 75% intelligible. The SLP could also further specify how intelligible speech is for different listeners (a spouse vs. a stranger), and for different settings (a quiet room vs. a loud restaurant).

It is also likely that more words will be understood if the listener knows the context of the conversation, such as a specific book or movie. There is also a greater likelihood of understanding more words  if the listening conditions are ideal, such as a quiet room with minimal distractions. Therefore, the SLP could write a statement in an evaluation such as, “Patient’s speech was judged to be 75% by the evaluating clinician, 85% by a familiar listener (patient’s spouse), 65% by an unfamiliar listener, and improves with context and ideal listening situations.”

What commonly happens to intelligibility in ataxia?

Intelligibility can become reduced in ataxia because of errors in the production of speech sounds, and/or disruptions in prosody. Intelligibility becomes particularly difficult in ataxia with longer words, such as statistics or Mississippi.

However, in a recent research study, people with ataxia generally had relatively high intelligibility at 70% or higher (Hilger, Cloud, & Fahey, 2022). This intelligibility is particularly high when compared with other neurological conditions such as Amyotrophic Lateral Sclerosis or Parkinson’s Disease, where intelligibility is often reduced to below 50%. On the contrary, the study found that naturalness in ataxia was greatly impaired, meaning how natural the pitch, loudness, and timing of speech were perceived. Overall, speech in ataxia is relatively intelligible, which has great benefits for communication.

How can intelligibility be improved in ataxia?

Research is still being completed to find effective therapies for improving intelligibility in ataxia. There is currently no gold standard for treatment. The main recommendation is to seek a referral for an evaluation by a speech-language pathologist to determine your own unique intelligibility difficulties, and what may be causing them.  Some potential goals could be to improve the production of longer, multisyllabic words, and to practice timing strategies that could help the speech articulators (lips, tongue, jaw) coordinate better.

One strategy people can employ outside of speech therapy is to find quiet areas to communicate with others. For example, if you are at a coffee shop, find an area that is quieter, away from the barista counter. Intelligibility will likely improve in quieter spaces.

Another strategy is to reformulate what you are saying if someone does not understand you, using synonyms or different phrasing. For example, if you say, “I work at the university,” and someone replies, “What did you say?” you could rephrase and say, “My employment, my job. It is at the university, the school nearby.”

Lastly, another strategy would be to provide context for what you are saying, such as, “The football game on Sunday. I thought that Mahomes played well.” As people listen to your speech over time, they should be able to understand it better and better.

If you would like to learn more about intelligibility, take a look at these resources by ClearTalk Mastery and the Informed SLP.

Snapshot Written by: Allison Hilger, PhD, CCC-SLP

Edited by: Celeste Suart, PhD

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