Like bats, some blind people utilize echolocation—bouncing sound waves off objects to locate where they are—as a means of assessing and interacting with their surroundings. To do this, some snap their fingers, while others click their tongues, Health Canal writes. While researchers have known about this skill for years, the degree to which it stands in for vision is poorly understood.
Neuroscientists from Western University's Brain and Mind Institute recently discovered that echolocation is a much closer substitute for vision that originally assumed. As they report in the journal Psychological Science, echolocation is so tightly associated with vision that it succumbs to the same shortcomings as that sense.
To determine this, the team set up three boxes ranging in size from small to large. Although the boxes' sizes were different, they all weighed the same. They asked people who have normal vision and blind people who both did and did not use echolocation to determine which boxes were heavier not by lifting them directly but by pulling on a string attached to each box, Health Canal describes. As expected, the people with normal vision fell victim to a common psychological trick called the size-weight illusion, in which smaller objects—even if they weigh the same as larger ones—are perceived as weighing more. They guessed that the smallest objects were the heaviest.
The blind people who did not use echolocation, on the other hand, correctly reported that all of the objects weighed the same. But those that did use echolocation fell victim to the same bias as the people who could see. They thought the smaller boxes weighed the most. As the authors told Health Canal, "This new study shows that echolocation is not just a functional tool to help visually-impaired individuals navigate their environment, but actually has the potential to be a complete sensory replacement for vision."
Here, you can see human echolocation in action: