Where does our sense of direction come from within the brain?
We have two ways of finding our way around: 'egocentric' and 'spatial' navigation. Michael Bond explains in this extract from his book Wayfinding.
Humans are blessed with an inner navigator that is immeasurably more sophisticated and capable than any artificial system. How do we use it?
Psychologists have found that, when finding their way through unfamiliar terrain, people follow one of two strategies: either they relate everything to their own position in space, the ‘egocentric’ approach, or they rely on the features of the landscape and how they relate to each other to tell them where they are, the ‘spatial’ approach.
The egocentric approach is like following a set of instructions: how many streets will I pass before I reach the turning? Should I turn left or right when I get there? The spatial approach, by contrast, involves taking a bird’s-eye view: where is my house in relation to that hill? Should I head south or west? Egocentric is following your nose; spatial is about the big picture.
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Both methods work, up to a point, and many of us use them interchangeably. Egocentric navigation is often simpler and quicker, and it makes sense to use it when regularly taking the same route (on your daily commute, for example).
But you shouldn’t rely on it all the time, because if one of your cues doesn’t match the reality on the ground – if a road is blocked or a landmark has disappeared – you’ll have no geographical knowledge to fall back on and no way of calculating a detour. Only a spatial strategy can give you a full understanding of your surroundings and where you are in relation to them.
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An egocentric view is a single-point construal, like a conventional photograph; a spatial view is more like a David Hockney landscape, full of depth and multiple perspectives.
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As you might expect, the two approaches use different parts of the brain. Egocentric route-following depends on two areas: a structure near the centre of the brain called the caudate nucleus, which is involved in movement control and the learning of habitual behaviours, and the posterior parietal cortex, which sits near the back of the brain and plays a big role in spatial reasoning.
Spatial navigation, on the other hand, is driven by the hippocampus, the brain’s map-maker. People who consistently navigate with a spatial approach have more grey matter in their hippocampus, presumably because they exercise it more; for egocentric navigators, the same is true of their caudate nucleus.
The obvious implication is that our brains respond to how we use them. (It could also be that egocentric navigators have dense caudate nuclei to start off with, and spatial navigators dense hippocampi.)
Studies on the psychology of navigation have found that in a general population, the ratio of egocentric to spatial navigators is around 50/50. Within that, there is great variation dependent on age, sex, culture, whether someone has an urban or rural upbringing, the state of their health and even whether they are left or right-handed.
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If you are a skilled navigator – meaning that you can find your way around an unfamiliar area while maintaining a sense of direction and an idea of where you are – then your default strategy will almost certainly be spatial. This is because effective navigation requires a cognitive map, which is harder to achieve with an egocentric strategy.
Skilled navigators, because they use a spatial approach, seem to have a more ‘muscular’ hippocampus – at least, this is what studies with undergraduate students have told us.
No one has yet analysed the brains of Inuit elders, Polynesian sailors, Aboriginal Australians, Alaskan fur trappers, US Army Rangers, Ordnance Survey cartographers, orienteering champions or other renowned ‘natural navigators’, but it is likely that they are all well-endowed in the hippocampal area.
If that’s the case, did practice make it that way, or were they born with ‘a wayfinder’s flair’? We can’t be sure.
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