Complicated Listening Environments:
How do Children with Hearing Loss Manage?
Have you ever found it difficult to get your children’s attention when they are watching TV? If your kids are anything like mine, it’s nearly impossible. My daughter can become so engrossed that she doesn’t hear me unless I put myself physically between her and whatever she is doing. As a hearing scientist, I’m intrigued by this problem. Why am I not able to draw my daughter’s attention away from what she’s doing by simply raising my voice? There’s clearly more going on here than just the signal-to-noise ratio. The term “signal-to-noise ratio” isn’t as technical as it sounds. It’s simply the level of the signal (me) compared to the level of the noise (the television). We’ve known for a long time that children need a better signal-to-noise ratio than adults to understand speech at their best. Children with hearing loss need an even better signal-to-noise ratio, and we take this into consideration when we fit them with hearing aids. But increasing the signal level doesn’t seem to do the trick when it comes to capturing a child’s attention. This can cause problems in some situations, especially for children who already have a difficult time hearing.
One way that we have studied this problem is to ask children to do two things at the same time and observe how they divide their attention. Typically, children are asked to do a listening task and some other kind of task that doesn’t involve hearing at all. For example, in a study conducted a few years ago, children were asked to repeat words and watch a light bulb at the same time. When the light turned on they were to push a button to turn it off (Hicks & Tharpe, 2002). The researchers knew that the children with hearing loss would not do as well as the children with normal hearing on the listening task because they had hearing loss. What they wanted to know was if the children with hearing loss focused more or less of their attention on the listening task because it’s more difficult. If they paid more attention to listening, they wouldn’t be as quick to push the button to turn the light off. But that didn’t happen. The children with hearing loss were able to monitor the light as well as the children with normal hearing even when noise was added to the listening task to make it harder. The same thing happened in two other studies using different tasks (McFadden & Pittman, 2008; Stelmachowicz et al., 2007). In every case, the children had no trouble with the competing task.
At first, we thought this meant that children with hearing loss don’t work any harder to listen than children with normal hearing. But that conclusion didn’t fit with the problems that parents and teachers often tell us about. That is, children with hearing loss have a harder time paying attention at home and in the classroom than children with normal hearing. So we took another look at the problem from a different point of view. In a recent study in our lab, we asked children to listen to words in some background noise and tell us if each word was a person, a food, or an animal. That meant that the children had to think about the word rather than just repeat it. At the same time, we asked them to play dot-to-dot games. By themselves, these tasks are easy and children with hearing loss do very well on both of them. But when they are put together, they become more difficult, and children have to divide their attention between the two tasks. To make things even harder, we gave the children dot-to-dot games that increased in difficulty (counting by 1s, by 2s, and by 3s) to see how it affected their ability to hear and categorize the words. It’s similar to what children do in school when they are listening to the teacher while working at their desk. We wanted to get an idea of how tasks that don’t require listening interfere with tasks that do.
The results revealed some interesting things about how children with normal hearing and children with hearing loss divide their attention. First, the children with hearing loss completed fewer dot-to-dot games than the children with normal hearing. That means that the children with hearing loss slowed down so that they could do both tasks at the same time. For the listening task, the children with normal hearing did equally well in all conditions but the children with hearing loss did worse as the conditions got harder. The figure shows how the children with hearing loss did when they were just listening (left chart) and when they were listening and playing the dot-to-dot games (right chart). Each graph shows the percentage of words they got right, the words they misunderstood (mistakes), and the words they didn’t respond to. Overall, the children did very well when they were just listening and their errors were mostly due to mistakes related to hearing loss. When they were asked to play the dot-to-dot games, however, they did worse. What’s interesting is that the only thing that changed was that they didn’t respond to more of the words (12%). Put simply, the children didn’t hear many of the words because they were busy playing the dot-to-dot games. (See figure above)
These results told us that the problem isn’t due to hearing loss alone but to cognitive resources as well. Cognitive resources are similar to mental effort. We all have a certain amount of mental effort that we can devote to one or more tasks. Although children with hearing loss have the ability to hear and perform these tasks well, it appears that hearing loss takes up more than its fair share of their cognitive resources. As their effort on the dot-to-dot games increased, they couldn’t sustain the same amount of cognitive resources for the listening task. These results are consistent with what parents and teachers tell us; that children with hearing loss have trouble doing everything that’s expected of them when things get complicated.
So what can we do for children with hearing loss in these situations? The answer, I believe, is to reduce the demand on their cognitive resources without reducing our expectations. The first and best thing we can do is provide them high-quality hearing aids to reduce their listening effort, and classroom amplification (such as personal FM systems) to improve the signal-to-noise ratio. After that, we can help by allowing them to concentrate on one thing at a time. For example, listening to the teacher and taking notes at the same time can be very difficult. Allowing for time to process what was said and then time to write it down would be helpful. These and other accommodations might seem simple but the benefits that children receive may extend well beyond better listening to a broad range of academic, social and vocational achievements. ~
Andrea Pittman, PhD CCC-A is an Assistant Professor, Speech and Hearing Science at Arizona State University.
Hicks, C. B. & Tharpe, A. M. (2002). Listening effort and fatigue in school-age children with and without hearing loss. Journal of Speech, Language and Hearing Research, 45, 573-584.
McFadden, B. & Pittman, A. (2008). Effect of minimal hearing loss on children's ability to multitask in quiet and in noise. Language, Speech and Hearing Services in Schools, 39, 1-10.
Stelmachowicz, P. G., Lewis, D. E., Choi, S., & Hoover, B. (2007). Effect of stimulus bandwidth on auditory skills in normal-hearing and hearing-impaired children. Ear and Hearing, 28, 483-494.