Cities are getting more complex. As they grow, their transportation systems become increasingly large and multimodal. Could those human-constructed environments exceed our cognitive capacity?

It is recognized that human brain has intrinsic cognitive limits for processing information. For example, the ability to manage complex “mental maps” is limited by the maximum number of objects people can track in their visual working memory, which is about four⁽¹⁾.

The authors of a paper⁽²⁾ published this week, wonder whether it is possible to quantitatively characterize our difficulty navigating current transportation systems in megacities, and whether such navigation exceeds our cognitive limits. They define an information measure to characterize the complexity of the 15 largest urban metropolitan systems in the world, and they manage to show that there would be a navigation analogue to the Dunbar’s number.

In the same way that there is a cognitive limit to the number of people with whom one can maintain stable social relationships—between 100 and 250 friends—, maps with more than 250 connection points would not be easily readable. They estimate that most trips in large cities exceed that human cognitive limit.

Their conclusion is clear. We need more technology to adapt our limited brain to the increasing complexity of cities:

The information-technology tools provided by companies and transportation agencies to help people navigate in transportation systems will soon become necessary in all large cities. Our analysis highlights the fact that humans need to integrate an excessive amount of information for urban navigation, and we therefore need to seek new solutions that will help them navigate in megacities.

Don’t throw your smartphone away yet!

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(1) Luck, Steven J., and Edward K. Vogel. ‘The Capacity of Visual Working Memory for Features and Conjunctions’. Nature 390, no. 6657 (20 November 1997): 279–81. doi:10.1038/36846.

(2) Gallotti, R., Porter, M., & Barthelemy, M. (2016). Lost in transportation: Information measures and cognitive limits in multilayer navigation Science Advances, 2 (2) DOI: 10.1126/sciadv.1500445