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People can learn to “see” with plastic whiskers attached to their fingers, heralding the potential of a next generation of sight aids that could take advantage of the human ability to adapt to new kinds of sensory perception.
A study from the Weizmann Institute has suggested that people can learn to use prosthetic whiskers to gain a better understanding of their surroundings just like a cat can.
Most mammals possess whiskers of some kind, thicker hairs that provide what is best understood as an extra kind of sense beyond sight, sound or touch. Whiskers, like all hairs, are made of dead cells, but at the root are a host of nerves that can translate whisker movements into tactile sensations. It’s hard to know exactly how that information is used by different animals — cats might use it to figure out which spaces they can safely fit through — but the key thing is that it gives them a bit of extra information.
Avraham Saig and his team from the Laboratory for the Study of Adaptive Perceptual Processing took a group of blindfolded subjects and attached a 30cm plastic whisker to each of their index fingers. They then sat them on a chair between two poles which were just beyond arm’s length on either side, so that they could only feel where they were with the whiskers (there’s a diagram showing the setup on the Weizmann institute’s site). The catch was that one of the poles would be positioned slightly further forward than the other one by a small gap of a few centimetres. The participants were asked to feel for the poles with their whiskers and work out which one was further back.
On the first day, the average point at which participants couldn’t tell the poles apart was a relatively large eight centimetres. On the second day, though, that gap was reduced down to three centimetres, and a few even managed to discern as small a gap as one centimetre. When the team looked at how people were improving their skills, they realised that most people were simply moving their hands backwards at the same speed and waiting to “feel” which side hit a pole first. As they had more practice at feeling with their whiskers, they weren’t getting better at feeling down the whisker — they weren’t getting more sensitive to the slight bending of the plastic — but rather they were just getting better at moving their hands slower and steadier near where they suspected the poles to be.
As Saig writes, this experiment whos that “changing our physical movements alone — without any corresponding change in the sensitivity of our senses — can be sufficient to sharpen our perception”. Our hand muscles are sensitive enough that they can turn a motion without any qualititave information into a rough picture of how things look.
In practice, this probably doesn’t mean blind people will be walking around with whiskers attached to their arms and legs to stop them banging into things, but there is the possibility of exploiting this phenomenon to develop new prosthetic aids for replicating the same sensation. That could mean some kind of small device strapped to the limbs with a camera on it that can turn what it sees into physical sensations on the user’s skin. Over time they could learn to interpret these signals into a way of “seeing” their way around, just like a cat figures out if it can fit its head inside a box without having to think about it.