Scrawny people tend to think approaching sounds are closer than do strong people, a new study found.
Scientists think this inclination might have evolved to help the weak escape from approaching danger. Back when humans were prey for large mammals, the less physically fit may have benefited from earlier warnings of incoming threats. Even now, it's probably helpful for the wimps among us to have a greater safety margin if, say, a piano is about to fall on their head.
Evolutionary psychologist John Neuhoff and colleagues at the College of Wooster in Ohio asked 50 people to listen to an approaching tone, and press a button when they thought the sound had arrived directly in front of them. The researchers found that almost everyone — about 98 percent of people — pressed the button somewhat early, even after going through 10 practice runs where the scientists told subjects when they were pressing too soon. The average lead time was 130 milliseconds, but some subjects jumped the gun by about 500 milliseconds, or half a second.
The psychologists also rated everyone on a physical fitness scale, based on recovering heart rate after exercise and grip strength. Strikingly, they found scrawny people consistently judged the tone to be right before them sooner than buff people did.
The work was inspired by Neuhoff's earlier research that showed the approaching sound bias is greater in women than in men. The researchers speculated that this effect might be caused by the different average strength levels of men and women, and decided to test the hypothesis. The new study lends support to this theory.
In trials people did not misjudge sounds that were moving away from them — only approaching sounds. This adds reinforcement to the theory that this behavior evolved as a buffer to keep people safe from approaching danger. Although we sacrifice accuracy in judging sounds' distances, we gain advance notice of danger. For prey species like humans, this seems to be a worthy tradeoff.
"The cost of responding early is not very great at all, whereas the cost of responding late can be fatal," Neuhoff told LiveScience.
In earlier research, Neuhoff and team found a similar bias toward approaching sounds versus receding sounds in Rhesus monkeys. They have not yet tested many other species, but are curious to see if the effect changes with predator animals, especially those that rely on accurate sound judgments to capture prey, such as bats.
"Our prediction is that if you're more likely to be a predator, you wouldn’t have the need for as great a bias, but if you're a bunny you need a larger margin of safety," Neuhoff said.
Neuhoff presented his findings May 21 at the 157th Acoustical Society of America Meeting in Portland, Oregon.
Copyright © 2009 Imaginova Corp. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.