India, March 13 -- We are in contact with more people today - conducting more social interactions and processing more information, on average - than would have been thought possible, through most of human history. How does this play into our sense of being overwhelmed?

According to the social brain hypothesis, humans can, on average, maintain about 150 stable, meaningful relationships at a time. This number was first proposed in the 1990s by the British anthropologist Robin Dunbar, who found a correlation between primate brain size and size of social group.

The size of the brain is a determiner "because a big chunk of our brain is required for social interactions", says Dunbar, now 77.

"It takes a lot more neural energy to analyse what...