While reading on a bus ride through a 1950s Buenos Aires, the Argentine writer Jorge Luis Borges suddenly saw the world dissolve before his eyes.

“The blind live in a world that is inconvenient, an undefined world from which certain colors emerge: for me, yellow, blue (except that blue may be green), and green (except that green may be blue),” he would later write in an elegy for faculty he’d lost without warning. “As for red, it has vanished completely.”

Borges, a man with an eye for the unimaginable, had found himself with a personal answer to the question that has strained our imagination for centuries: What, if anything, do blind people see?

Research suggests that, although people born unable to see cannot detect visual stimuli, their brains still interpret certain information as visual. One example is a new study from the Hebrew University of Jerusalem, where neurobiologists have determined that blind people can learn to “see” other bodies using only their ears.

Although it may sound strange at first, this type of navigation is fairly common in nature. "The idea is to replace information from a missing sense by using input from a different sense," Amir Amedi, a professor of neurology and senior author of the study, said in a press release. "It's just like bats and dolphins use sounds and echolocation to 'see' using their ears."

Published in the journal Current Biology, the new findings suggest that blind people can learn how to do this with the help of certain algorithms that translate visual data into sounds. To investigate, the researchers first taught participants to perceive simple dots and lines. They then gradually worked their way to more complex shapes.

"Imagine for instance a diagonal line going down from left to right; if we use a descending musical scale—going on the piano from right to left—it will describe it nicely," Ella Striem-Amit, doctoral candidate and lead author of the study, explained. "And if the diagonal line is going up from left to right, then we use an ascending musical scale."

With no more than 70 hours of training, the average participant was able to recognize the shape of a human body. What’s more, they were able to detect and imitate exact postures. Brain scans later revealed that their visual cortex — that is, the area responsible for processing visual data — lit up with activity during these tasks.

According to Amedi, the findings have great therapy potential. The lab’s app, EyeMusic, which scans images and transforms them into soundscapes perceptible by the blind, is already available. "We're beginning to understand [that] the brain is more than a pure sensory machine," Amedi explained. "It is a highly flexible task machine. The time has come to revive the focus on practical visual rehabilitation with sensory substitution devices."

Source: Striem-Amit E, Amedi A. Visual Cortex Extrastriate Body-Selective Area Activation in Congenitally Blind People “Seeing” by Using Sounds. Current Biology. 2014.