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Hear Today Gone Tomorrow

September 15, 2009
by Stacy Finz
image of "The Last Supper" by Leonardo da Vinci

It’s that all-important third date, the one where she’s ready to tell you everything, even that embarrassing story about her ex. Just as she begins to talk, the group of advertising executives at the table to your right gets animated, while the waiter on your left begins a lengthy recitation of the daily specials. You lean in and manage to hear her every word. But you remember nothing.

That’s not surprising. Researchers at Cal’s Auditory Perception Laboratory in the Department of Psychology have found that background noise—particularly speech babble—can wreak havoc on recall and the ability to multi-task. For the last three years, professor emeritus Ervin Hafter and post-doctoral research fellow Anastasios Sarampalis have been measuring listening effort. The duo teamed up with Berkeley’s Starkey Hearing Research Center to study both normal-hearing and hearing-impaired listeners. The objective of the “Cognitive Factors in Hearing Aid Research” study was to determine how noise affects people’s ability to retain information and to perform simple tasks. Ultimately, the researchers will use their findings to perfect hearing aides.

In one experiment, subjects listened to sentences in quiet situations as well as noisy ones, then were asked to repeat the last word of the sentence. “We also asked them to try to remember their answers and at periodic intervals asked them to recall them,” Sarampalis said. The researchers found that as background noise increased, making it harder to hear, “recall performance went down.” As the background noise reduced, they found that “the task of listening to speech in noise became less effortful,” so the subjects expended more energy remembering words they were meant to recall.

In another experiment, they played with listening and reaction time. Again, subjects were told sentences in both quiet and noisy situations and were asked to repeat them. They were also required to perform a demanding task on a computer keyboard. Once again the researchers found that as listening became more difficult, reaction time on the task became slower.

The way Hafter describes it is, “The subject is working so hard to extract speech from noise that it’s too exhausting to do anything else.”

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