Face masks have changed our use of language. It affects how children understand speech

OAlthough wearing a mask is no longer required in many places, it is still used as a means of limiting the spread of COVID-19. One of the criticisms of masks is that they make communication more difficult. A recent report from UK Department of Educationfor example, suggests that mask-wearing during the pandemic has caused communication difficulties in classrooms.

However, our new search shows that for people without hearing and language difficulties, the effects of face masks on speech understanding are actually mild.

Although face masks slow down our understanding of speech, they rarely lead to misunderstandings. Masks also do not affect our understanding in all situations. They usually only have an effect when the topic of conversation is unpredictable.

26 children (8 to 12 years old) and 26 adults without hearing or language difficulties participated in our study. We showed them videos of someone talking while wearing a cloth face mask and asked them to repeat the last word of every sentence they heard. This allowed us to measure how quickly and accurately people understand masked speech.

In addition to testing our participants’ understanding of masked versus unmasked speech, we also manipulated the video to separately test the audio and visual effects of masking. This meant that, for example, the video showed an unmasked speaker but played audio recorded with the mask on.

We found that children process masked speech up to 8% less accurately and 8% slower than normal speech, while adults process masked speech up to 6.5% less accurately and 18% slower.

In general, the adults responded to speech faster than the children in the study – about 23% faster (148 milliseconds) when listening to speech with a face mask and 29% faster (176 milliseconds) when they listen to normal speech. The very efficient processing of normal speech by adults could be one of the reasons why the effect of face masks on their speed is more pronounced.

The impact of face masks

Face masks change our use of language in two ways. They change the sound of a speaker and can give the impression that their speech is muffled. Most masks also block the view of the speaker’s lips.

Surprisingly, our research shows that the way masks alter the sound when we speak affects children more than the visual obstruction of the speaker’s lips. The reason may be that children are not as good to combine visual information with sound as adults do when they hear and see a speaker. Therefore, seeing the speaker’s lip movements while hearing masked speech does not improve the accuracy with which he understands what is being said.

This is different from adults, who find masked speech more difficult to understand due to the unique combination of visual blocking and sound changes. We found that acoustically muffled masked speech does not affect adult comprehension when they can see the speaker’s lip movements. Similarly, masking the speaker’s mouth has no effect when the speech sound is clear. However, most masks hide the mouth and change the sound of speech at the same time.

What we talk about matters

Interestingly, the subject of the conversation is important. Face masks affect our understanding less when we can anticipate what our interlocutor is going to say.

Indeed, knowing the context of the conversation helps us understand language quickly and effortlessly. For example, in the sentence “For your birthday, I made this cake”, the words “birthday” and “baked” have a meaning related to the last word “cake” and often appear together. Our brain can use this information to predict what a speaker is going to say.

Our study shows that giving this type of contextual information reduces difficulties in understanding masked speech. When given high contextual information, children and adults process masked speech with only 1% less accuracy than normal speech. This explains why communication with masks poses difficulties in some situations but not in others.

Although there are concerns that masks will affect children’s learning, teachers are using many techniques in the classroom that increase contextual information. They design lessons in a way that builds on students’ existing knowledge and uses pictures, keywords, and written text. All of these techniques help children understand what is being said and help them compensate for the effects of the face mask.

Listeners also use other cues that reduce masking effects. For example, most masks do not cover the upper part of the face. This is good news because seeing the speaker’s eyes and upper face helps us understand masked speech better. As a result, our understanding of language is remarkably robust.

However, participants in our study did not have hearing or speech difficultiesand only listened to an adult speaker in calm conditions. We don’t know how mask-wearing affected children’s communication with their peers, or its impact on other aspects of their learning and welfare.

Julia Schwarz is PhD Candidate in Linguistics, University of Cambridge
The article was first published in The Conversation.

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