Human brains normally suppress echoes, but they can use the sounds to echolocate in some situations.
Credit: Eduard Stelmakh | Shutterstock
Blind humans have been known to use echolocation to "see" their environment, but even sighted people can learn the skill, a new study finds.
Study participants learned to echolocate, or glean information about surroundings by bouncing sound waves off surfaces, in a virtual environment. Although the human brain normally suppresses echoes, it perceives them when a person uses echolocation, the research showed.
Bats, dolphins and porpoises use echolocation to navigate and hunt. In humans, reports of blind people using sounds to orient themselves go back to the 18th century, but the phenomenon has been less well-studied in sighted people.
"This study found that sighted people can echolocate, in good agreement with past studies," said neuroscientist Lore Thaler of Durham University in England, who was not involved with the research. [7 Amazing Superhuman Feats]
But in contrast to previous studies, the current one looked at echo suppression — the phenomenon by which the human brain suppresses the sound of echoes so the original sound can be heard clearly. This ability is very useful, Thaler told LiveScience. "Otherwise, speech would be virtually unintelligible," she said.
In the study, sighted participants wore a headset with a microphone. In a "listening" experiment, the participants heard sounds and simulated echoes through the headphones, and they had to discriminate between the positions of the sound source (the leading sound) and its echo (the lagging sound).
In an "echolocation" experiment, participants made the sounds, such as mouth or tongue clicks, themselves. A computer processor simulated the echoes these sounds would produce when hitting a reflector, and played them back through the headset.
Sighted individuals learned to perceive the positions of reflectors in the echolocation experiment just as well as they perceived the position of the sound source in the listening experiment, the researchers showed.
They found that in the listening experiment, perception of the leading sound caused the lagging sound (the echo) to be suppressed in the brain. But in the echolocation experiment, both leading and lagging sounds were perceived equally well, suggesting the echo suppression diminished during echolocation.
So if humans can echolocate, why don't they do it all the time? "Unless you run around in dark environments or blindfolded, echolocation is just not needed," Thaler said. While the study shows that sighted person can learn the skill, blind people are typically better at it, she said.
Individuals who lack sight may be more attuned to the auditory environment. Or brain resources typically used for sight may be directed toward hearing, Thaler said.
Still, "I think [the new study] is an interesting piece of evidence," Thaler said, adding that she would be curious to see how blind people would perform in the experiment.
The findings were detailed Tuesday (Aug. 27) in the journal Proceedings of the Royal Society B.