From an evolutionary perspective, it’s good to be twitchy: Any change to our sensory environment – a sudden sound, a jarring sight, an alien smell – represents a potential threat.
But cities take distraction to a level undreamed of on the primeval savannah, to the point where the urban form itself can be blamed for messing with our minds.
“In the 19th century,” says Hillel Schwartz, a social historian and author of Making Noise: From Babel to the Big Bang and Beyond , “you get this notion that living in the city can be nerve-wracking, that the city itself can cause people to have a mental collapse.”
Recent studies by scientists at Heidelberg University’s Central Institute for Mental Health support this view. In trying to determine why rates of schizophrenia are much higher in people raised in the city, they showed that city types experience a heightened stress response in the amygdala, the part of the brain that processes emotion.
Putting the brain on park
If there are specific aspects of the city that are hard on the brain, urban design can be used to reduce these pressures. Studies by Marc Berman, a researcher at the Rotman Research Institute in Toronto, suggest that an environment along the lines of a Stanley Park or Mont Royal can have a beneficial effect: Urbanites who took a short break in a natural setting of trees and water performed better on memory and attention tests than those who wandered a busy city street.
The brain has a remarkable ability to focus, shutting out extraneous stimuli to find a place of relaxation and creativity. When the detective story you’re reading is sufficiently gripping, you will go temporarily deaf because you’re inhabiting another world. That magical ability just doesn’t transfer well to a city intersection.
Focus has its limitations, even in the animal world: A street-smart cat will suddenly dart into the path of a car when he’s fixated on turf battles with his rivals. And so, too, a shopper intent on picking out a favourite brand of cereal in the densely packed, attention-craving supermarket lanes will miss the imminent collision from an oncoming shopping cart – steered by another granola-seeking brain.
The processing capacity of the brain is limited, since there’s a tradeoff between increased skull size and the advanced human ability to walk upright. So the scenes of the world we think we’re partaking in are actually a highly partial composite of reality based on 200,000 rapid eye movements every day – snapshots of the exceedingly tiny bits we’re interested in.
Our peripheral vision may be reassuringly extensive and Gretzky-like – 150 degrees in scope – but the amount we actually see at a single moment, with any degree of detail and colour and sharp-edged focus, is less than three degrees.
“Most of the time, over most of the visual field, we’re mostly blind,” says Prof. Pratt.
The fact that a store shelf can stretch us to our limits is no cause for existential despair. From the brain’s point of view, says Prof. Pratt, “it’s actually an amazingly complex visual scene.”
The key thing for the urbanite is to recognize this complexity, and the demanding effect it has on our brain, for better and for worse. Since the organ in our heads is designed to be on a constant alert for differences, the city becomes a place of hyperalert vigilance.
“This leads to two entirely different theories of how we encounter the city,” says Mr. Schwartz. “One, people need to be stimulated and the city is a learning machine. Or two, the city is a place where people are overstimulated, where we have too many things thrown at us.”
The greedy gears of perception
Both versions could be true, of course. Some people can carry on an intelligent conversation in the boisterous restaurant of the moment. Other people hear nothing but ambient noise and can’t wait to escape.