Test subjects listened to a sophisticated sound system that mimicked the approach of a motorbike on a highway.
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OREGON, U.S.: Unfit or weak people react sooner to sounds of approaching danger than strong, healthy people – which may be an evolutionary adaptation to allow them a larger margin of safety, says a new study.
Test subjects listened to a sophisticated sound system that mimicked an approaching object, explained John Neuhoff, an evolutionary psychologist at the College of Wooster in Ohio, U.S., and co-leader of the study.
The 'virtual object' sounded like a motorcycle passing on a highway, approaching the subject at 15 m/s and then whizzing past them. The subjects were asked to hit a key when they thought the sound was right in front of them.
Fitness was measured by two variables: heart rate after a bout of moderate cardiovascular exercise and muscular power, measured by the strength of their hand grips.
Everyone underestimates time of arrival
Almost everyone underestimated the time of arrival, hitting the key before the sound had actually arrived. But people who were less physically fit hit the key sooner than those who were more fit, Neuhoff reported at the Acoustics Society of America's annual conference held last week in Portland, Oregon.
"It's beneficial [for the weaker] to react sooner rather than later," said Neuhoff. "The cost of responding too early is far less than the potentially fatal cost of responding too late."
This bias in perception is only in response to approaching virtual objects. There is no difference in response time for virtual objects that are retreating.
"Looming sounds are biologically important stimuli," he said. If a person's ability to overpower or run from danger is diminished, it makes sense that an adaptive mechanism like a quicker response time might have evolved.
Selective advantage
"Responses to looming sounds are scaled to the motor system's ability to react," said Neuhoff, and that is directly related to how physically fit an individual is.
The difference is less than a second. Nevertheless, "this systematic perceptual error might provide a selective advantage," said Neuhoff. "Perceptual bias might be a behavioral adaptation shaped by evolution."
Women typically responded sooner than men, who on average are physically stronger. Plus comparative studies in Rhesus monkeys showed the same biases, suggesting a biological basis for the results. But the research is still in its infancy.
"It makes some ecological sense that there is this particular bias, but there are a lot of variables," commented Norbert Copco, a researcher at the Department of Cybernetics and Artificial Intelligence at the Technical University of Kosice in Slovakia, who also presented a paper at the meeting.
He noted that if this is effect is real, then older people, whose ability to defend themselves is lower, should also react sooner to approaching sounds.
Neuhoff agreed that more research is needed. "We still need longitudinal studies, looking at physical fitness over time."
