The shortest distance between two points is a straight line but when walking down the street it is not always possible, so how do you choose the best route?
Based on information provided by the mobiles of more than 14,000 anonymous people , the team found that pedestrians tend to choose the paths that appear to point most directly to their destination, even if those routes end up being longer. It is what they call the “most cutting edge path”.
This strategy, known as vector navigation , has also been observed in studies of animals, from insects to primates.
In their study, published yesterday in Nature Computational Science , the MIT team suggests that vector- based navigation – which requires less brain energy than calculating the shortest route – may be an evolutionary consequence for the brain to devote more energy to other tasks. .
“It seems that there is a trade-off that allows us to use the computing power of our brain for other things: 30,000 years ago, to avoid a lion, or now, to avoid a dangerous SUV,” explains Carlo Ratti , professor of urban technologies in the Department of Urban Studies and Planning of the MIT.
One way to go, and a different way to return
Ratti began ruminating on this study when he was a graduate student at Cambridge. Every day he walked the path between the residence hall and the university until one day he realized that, in fact, he was following two different routes : one going to the university and a slightly different one back. Years later he wanted to know why.
To find out, he used the mobile data of more than 14,000 people who lived in urban environments, data from GPS signals that contained more than 550,000 journeys made by pedestrians while walking through Boston and Cambridge (Massachusetts) over a year.
Their analysis showed that, instead of choosing the shortest routes , pedestrians chose slightly longer routes that minimized their angular deviation from the destination, that is, they chose paths that allowed them to face their end point more directly when starting the route. although a path starting to the left or right could be shorter.
“Instead of calculating the minimum distances, we found that the most predictive model was not the one that sought the shortest path, but the one that tried to minimize the angular displacement, that is, to point directly towards the destination as far as possible, although traveling at greater angles would actually be more efficient, ”says Paolo Santi , a researcher at the Italian National Research Council and co-author of the study.
The analysis found that this behavior was repeated both for pedestrians in Boston and Cambridge, which have a convoluted street network, and for those in San Francisco, which has a grid-shaped street layout.
They also found that people tended to choose different routes when making a round trip between two destinations, much like Ratti did as a student.
“When we make decisions based on the angle to the destination, the street network takes you down an asymmetrical path. Based on thousands of pedestrians, it is very clear that I am not the only one: Human beings are not an optimal navigator ”, concludes Ratti.