Blind people able to use array of bat-like clicks as 'sonar' to sense their surroundings

Some blind people have the ability to visualise their surroundings using sound, and in a new study scientists have worked with a group of these “expert echolocators” in an effort to unravel this poorly understood ability.

Human echolocation is a remarkable skill similar to the technique used by bats and whales to hunt prey.

It has drawn comparisons with sonar, as practitioners use reflected sound waves to build mental maps of the world around them.

Echolocators can find their way around by making noises – for example clicking their mouths – and then listening for the echoes from nearby objects.

Some individuals, such as the American echolocation expert Daniel Kish, have developed particularly advanced abilities.

Mr Kish, who is sometimes referred to as “Batman” is able to find his way around despite being totally blind, and can even hike and ride a bike.

While individuals using echolocation have been known about for some time, it is only in recent years that scientists have begun to properly analyse their skills.

In a new study, a team of researchers led by psychologist Dr Lore Thaler at Durham University set out to understand this ability in greater detail.

Specifically, the researchers wanted to find out how echolocators adjust their clicks in response to variations in their surroundings to create complex “mental maps”. To this end, they enlisted eight blind expert echolocators to have their abilities put to the test.

By understanding the nuances of echolocation, the scientists hope to use the information to help other blind people learn to echolocate.

“Just from walking around with people who echolocate, I know anecdotally that this is a very flexible behaviour – so sometimes they are soft, sometimes louder,” Dr Thaler told The Independent.

“This was a way to really quantify how they adjust the clicks that they make.”

Analysis of the expert echolocators in full flow revealed they dynamically adjust the loudness and number of clicks they make in order to detect objects in different positions around them. The researchers used dinner plate-sized targets to assess this.

When these objects are located further away from the beam of sound emitted from an echolocator’s mouth – off to the side, for example – the individuals increased the number or volume of their clicks to compensate for the poorer quality echo bouncing back at them.

The only position at which the echolocators found it difficult to assess the location of an object accurately was when it was placed directly behind them.

The researchers recorded the noises made by their participants, as well as the corresponding echoes from the targets. These recordings revealed the previously unacknowledged extent of the echolocators’ abilities.

“We could actually quantify the loudness of the echoes, and the relative difference in loudness between the click and the echoes that people made,” said Dr Thaler.

“We found that in some conditions they were really faint – about 95 per cent softer than the actual clicks, but the echolocators were still able to sense this. They could perceive the echoes.”

This was a surprise as previously scientists have argued that detecting such quiet echoes should be impossible.

The researchers concluded that the brains of those who perform echolocation have actually been remodelled so they are capable of picking up on even the quietest sounds.

“With these expert echolocators, they must have adapted their auditory system to the degree that they can perceive very faint echoes.”

The findings from these experiments were published in the journal Proceedings of the Royal Society B: Biological Science.

While many learn to echolocate by themselves, it is also seen as an important skill that can be taught to blind people. With his organisation World Access for the Blind, Mr Kish has taught hundreds of children to echolocate.

By getting to grips with the abilities of expert echolocators, Dr Thaler and her colleagues hope to provide a useful toolkit for those who wish to learn.

“The applied value is that we can give people very precise instructions – make louder clicks, make more of them,” said Dr Thaler.

“Echolocation is a useful skill – but it’s a tool that goes together with other tools like guide dogs and canes. It is a good complement, and practice makes perfect,” she said.

“Not everyone will become like Daniel Kish, but obviously people can get really good at this.”