Can science explain why some transit system maps are so much better than others? Alex Hutchinson has an excellent article in the Canadian newsmagazine The Walrus on how increased reliance on Global Positioning Systems (GPS) for navigation may be reshaping our brains. Might this be related to the difficulty of getting good maps of a transit system?
Humans have two methods of navigation. Spatial navigators can construct maps in their heads as they experience a place, and also tend to be good at using maps as navigational aids. Narrative navigators navigate by creating or following verbal directions. For spatial navigators, the answer to the question where? is a position in mapped space. For narrative navigators, the answer to where? is a story about how to get there. Obviously, this is a spectrum; many of us are in the middle with partial capabilities in both directions. (I think we probably all know this from our own experience, but according to Hutchinson, the definitive academic study showing this difference has the amazingly recent date of 2003.)
Taxi drivers, obviously, have to be spatial navigators, because they must constantly plot courses for trips they've never made before. Before the advent of GPS, this requirement actually shaped their brains. Hutchinson writes:
A cognitive map featuring that level of detail, as you might imagine, requires a fair amount of storage space, and, sure enough, University College London neuroscientist Eleanor Maguire found that the back part of the hippocampus in London taxi drivers is enlarged compared with that of the general population. The longer they’ve been driving, the bigger the gap. Maguire also found, though, that the front part of the hippocampus gets correspondingly smaller. “So there is a price to pay for their expertise,” she says. This difference showed up in tests of visuo-spatial memory, including one in which the drivers were asked to memorize the position of sixteen objects on a table, then put them back in place after they’d been removed. “They were incredibly poor at doing that,” she says. While it isn’t yet clear whether this happens because the requirements of storing a map of London take over other parts of the brain or because of some other process, what these studies do make clear is the brain’s plasticity: its very structure is shaped by the demands we place on it.
Hutchinson goes on to suggest that the part of our brains that can remember maps is going to diminish as we all come to rely on GPS navigation systems. Many taxi drivers today rely on those systems for everything, and it's often apparent, if you chat with them, that they lack the mental map of the city on which the previous generation relied. Of course, they may be more likely to know where their keys and wallet are, so on balance that could be a good thing.
But I suspect some people will always need and want maps. In fact I hope so, because only with a spatial understanding of your city can you be attentive to certain of its possibilities and needs. Ideally, we'd get good training as children on how to develop both capabilities.
Meanwhile, I wonder if the difference between spatial and narrative navigation lies at the core of the very common mutual incomprehension between the planning and marketing departments in transit agencies. It is a common complaint of planners that marketers don't understand the values that drove the design of the network and therefore aren't promoting it in ways that feature those values. Marketers, in turn, can claim that the planners are talking in abstractions and don't know how to connect with the typical user. Planners must be spatial navigators, but marketers are often experts in crafting stories, comfortable with narrative, and this can correlate (I realise I'm conjecturing here) with a preference for narrative navigation. (Again, most of us are on a spectrum between these extremes.)
To take a really obvious example, most transit planners understand the foundational role of frequency (how often a service runs) and span (how early or late it runs) in determining the usefulness of a service, so they tend to understand the value of Frequent Network mapping, which highlights the frequent all-day services to show you where you can go without waiting long. In this example from Metro Transit in Minneapolis (click to enlarge) the detail of all services is very complex, but yellow highlight draws your attention to the Frequent Network where you can count on service within 15 minutes.
Like the Walkscore maps showing where you can get to on transit in 45 minutes, Frequent Network maps are designed to be useful to spatial navigators who want to see their options in map form. To an extreme narrative navigator, frequency and span are abstractions. If you're following the directions of a trip planner, you don't need to know how frequent a service is or how late it runs. The trip planner tells you when it comes, and that's all you need to know.
Conjecture: Is the low informaton content of many published transit maps -- notably the failure to distingush visually between a route that runs every two minutes all day and one that runs once every Wednesday -- perhaps an expression of the fact that marketing managers, in whom these maps are usually entrusted, often tend to be more narrative than spatial in their own navigation? What would happen if transit agencies entrusted map design exclusively to people who navigate spatially, and who are therefore intensely sensitive to a map's quality and information content? By the same token, the design of trip planning software, which produces narrative directions about how to get somewhere on transit, should be entrusted to narrative navigators. Only a spatial navigator can tell you if a map works. Only a narrative navigator can tell you if directions do.
In the comments, I'd welcome pointers to data that goes one way or the other on this question. I'm throwing out an idea here, not expressing a fixed opinion. The one thing I'm sure of is that my brain is as distorted as a London taxi driver's, so I need help from yours!