January 24, 2022 1:57 pm

This is how the brain’s ‘navigator’ calculates the shortest route

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?

Well, according to a study of the Massachusetts Institute of Technology (MIT), in the US, our brain is not prepared to calculate the shortest path, but the most ‘pointer’.

Based on information provided by mobile phones of more than 14,000 people anonymous, the team found that pedestrians tend to choose paths that appear to be pointing straight more direct towards your 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 on animals, from insects to primates.

Pedestrians tend to choose the paths that seem to point most directly to their destination, even if those routes end up being longer.

In his study, published yesterday in Nature Computational Science, the MIT team suggests that navigation based on vector —Which requires less brain energy than calculating the shortest route— may be a evolutionary consequence so that the brain dedicates 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,” he explains Carlo Ratti, professor of urban technologies in the Department of Urban Studies and Planning at MIT.

And although vector-based navigation does not achieve the shortest path, “it is quite close and is very easy to calculate,” the researcher reasons.

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 he was actually 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, GPS signal data that contained more than 550,000 trips performed by pedestrians while walking through Boston and Cambridge (Massachusetts) over the course of a year.

Their analysis showed that instead of choosing the routes shorter, pedestrians chose slightly longer routes but minimized their angular deviation With respect to the destination, that is, they chose paths that allowed them to face their final point more directly when starting the route, although a path that began to the left or right could be shorter.

The study used data from GPS signals that contained more than 550,000 journeys made by pedestrians while walking through Boston and Cambridge in the United States.

“Instead of calculating the minimum distances, we discovered 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, ”he says. Paolo Santi, researcher of 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 observed that people tended to choose different routes when they made a round trip between two destinations, just like Ratti did in his student days.

“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.


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