Some people who are blind learn the extraordinary skill of echolocation, using mouth clicks to explore their environment in a way comparable to how bats navigate. Echolocation is typically used alongside a cane or guide dog and gives an impression of the person’s broader surroundings.
Now scientists have uncovered new insights into how this feat is performed, which could help others to learn the skill.
The study confirms that people can identify objects with a high rate of accuracy by listening for echoes of mouth clicks and that they make subtle alterations to their clicking patterns depending on the object’s location.
Most people who are born blind are highly sensitive to the acoustics of their environment – using the echoes that bounce of objects, walls and buildings to navigate and avoid collisions. However, in recent years there has been a growing awareness of the ability of some blind individuals to use mouth clicks to actively echolocate. One American echolocation expert, Daniel Kish, uses the technique to accurately build up a mental sketch of a room as well as using it to go mountain biking along new trails.
Lore Thaler, who led the work at Durham University, said to The Guardian: “From a scientific perspective, it’s firmly established that people can do this.”
Thaler said that the skill often emerges spontaneously in children, as they experiment with ways to explore their environment. “We’ve found they end up doing similar things, even though they’ve developed the skill independently,” she added.
In the latest study, eight expert echolocators were given the task of spotting whether a 17.5cm disc was present in their environment. The researchers placed the disc one metre from the volunteers at a range of angles. The volunteers were 100% accurate in spotting the object when it was directly in front of them, but their success rate dropped to 80% when it was slightly behind them and 50% – no better than chance – when it was directly behind their back (head movement was not allowed).
Participants tended to instinctively increase the number and volume of the clicks when the object was further behind them, the study found, mirroring the type of adjustments made by bats when navigating using sonar.
Knowing the types of strategies experts use could help train other visually impaired people in echolocation, Thaler hopes. “It’s a very learnable skill,” she added.
The technique is typically used alongside a cane or guide dog – not as a replacement – but can help avoid collisions with objects at head height and gives an impression of the broader surroundings, which other aids cannot do.
“It gives you an impression of larger scale space, which some people who are blind from birth can really struggle with,” said Thaler.
The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.