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It’s the feeling of direction: we feel that we have to go ‘that way’ to get back to your car; or that we can look at a map and get a sense of the layout of a place, and all those other very useful capabilities of space most of us have.
But knowing a little bit about something just raises a lot more questions. So how does our perception of space and direction really work? What is it that brain areas like the hippocampus are actually doing? Which sensory modalities are involved, and how? And how could you learn a sense of direction if you didn’t have one, or improve the one you have?
It’s questions like this that Frank Schumann, a post-doctoral researcher in the science of perception at Université Paris Descartes, tries to tackle through experimentation.
“Space is not in the brain, space is in the world”, he tells me. “And perceiving a location or direction is also not just performed by your brain. Spatial perception is something we only get by interacting with the world. And it turns out, how we act makes a difference to how we perceive locations and directions.”
During his PhD, Frank acted as a project leader in the feelSpace project at the University of Osnabrück to probe if the brain can learn a novel, artificial sense that gives information about space. His group devised a haptic compass belt embedded with 32 fast piezo-ceramic vibrators around its circumference. The one that points North vibrates continuously. As you turn, the vibrating actuator switches quickly to the one that’s now the north-most, providing you with continuous cues about your direction relative to the earth’s magnetic field.
Many birds have this sort of innate sixth sense of magnetic directions. And that’s how they’re able to accurately migrate over thousands of kilometres without maps or a sat-nav.
“The belt initially feels like a little buzzing that is sliding around you,” says Frank. “What we wanted to discover was whether the brain, given some time, would pick up that this extra cue relates to oneself in space, and begin to actually use it for orientation.”
“So did it work?” I ask.
“It kind-of worked,” says Frank.
“The first pilot had four people. Initial reactions seemed very positive. Some of the participants reported that the belt changed the way they felt space, for instance that it had become larger or more ordered, that the tactile buzzing became less prominent, and that this could potentially be very useful.”
“We immediately thought blindness was a condition for which the belt signal could possibly be a real help.”
“But actually it wasn’t. We had a participant, Paul, who’d been blind from birth and visited the Hamburg zoo over many weeks to test if Paul’s orientation improved by training with our belt. But the buzzing from the belt had no meaning for him. And in fact, ‘north’ had no useful meaning for him. And this did not change, at least not on its own.”
It comes down to our early-years discoveries as very young children; how we discover orientation and space.
“We have myriads of inputs, normally, visual cues, but also sounds and vestibular signals, that each work in a very specific way. But in the beginning, most of those cues don’t speak for themselves. They are meaningless for the brain until we start moving in space. Once we move, we can learn how each of these cues work. For instance the fact that every time we move to the right, our input to the eye from the house in front of us moves to the left.”
Frank’s new supervisor in Paris, Kevin O’Regan, discovered that, at some point, our brain ‘masters’ the cues and that it is then when begin to feel consciously oriented in a space. The felt space has properties like directions – what’s in front, behind or at our sides. We use this sense of a map to navigate between places.
At the scale of a city, our sense of direction is very much rooted in our sense of sight. It is natural for us that if we go round four sides of a square building, then we end up in the same place. And we know we’re in the same place because we can see it is.
Then we develop a sense of locality according to what’s immediately around us as far as we can walk. Vision allows us to fix landmarks that become the centres of our world, and then learn their relationship to other sub-geographies around them for as far as we can see.
“When somebody was born blind, they often don’t make these same discoveries. They tend to learn routes rather than have a map in their minds. People born blind might describe a local shop’s location as a series of instructions: ‘turn left out of the house, turn right at the second corner and go ahead for around three minutes’. A bit like the way sighted people use the subway in a new city. They know that they have to enter at Piccadilly Circus and get off at Baker Street. But they do not feel what direction Baker Street is from Piccadilly Circus.
In a way, the belt signal works a bit like vision, in that it gives you a stable orientation over a large spatial scale: magnetic north. Since the magnetic north pole is even further away than our line of sight, it allows learning a larger spatial map, and linking it sub-geographies that are further away. Which might explain why the sighted subjects felt their space grow larger.
It seems Paul on the other hand, could not relate the belt signal to an internal map of the area, because he likely didn’t build a map he could relate it to. He used a verbal, routed-based strategy for navigation, in which the belt signal did not give useful meaning.
“So when colleagues next tried the experiment with the belt, they worked with participants who had become blind later in life. These participants had already developed a map-based navigation behaviour in their early childhoods. And as we predicted, they understood intuitively how the belt’s vibration relates to direction and could be used to lead them to places on using their felt map.”
But interestingly, once we explained the layout of the zoo to Paul, he could very slowly start using the belt signal to train a map of the zoo and find his way around using the belt as well. So it seems the belt signal is initially more difficult for early blind individuals, but then potentially also more useful.
And what about the opposite case? People with a very strong sense of direction?
“Most of them seem to get their stronger sense of direction also by training. For instance, taxi-drivers in London are forced to constantly orient themselves and the longer they do this, the greater their sense of direction gets. It seems they are making more and more connections within their inner map.”
“And there are a few cultures that use a language for places that has global descriptions – ‘this place is in the North East of the town’ – rather than relative descriptions – ‘this place is near this other place’. The cultural custom and the language, a bit like our belt signal, makes them continuously track the position of places in absolute space, and this seems to structure their inner map in absolute relations.”
How would you judge your sense of direction?
image credits: belt prototypes and navigation test - cc -Frank Schumann