Ever wondered why as soon as you step onto a crowded commuter train, there is an unspoken rule that you must not speak to the people around you? Even accidentally catching someone's eye at the other end of the carriage can make you feel like a wandering-eyed weirdo who has overstepped the mark.
But there's a reason for all this silence, according to psychologist Walter Bradford Cannon - being surrounded by strangers makes us feel nervous, and sets off one of our most basic fear-induced reactions: to freeze like a frightened animal.
Just like a bunch of startled wildebeests on the savannah after they sense an approaching lion, none of us wants to be the one to start making noise and draw attention to ourselves. By refusing to acknowledge the other people around us, we are “playing dead”.
In the book Adapted from Rush Hour, How 500 Million Commuters Survive The Daily Journey To Work, Cannon says while we are often told about the instincts of “fight” and “flight”, this third response kicks in when we are confronted by a large number of unfamiliar people without anywhere to run.
If you observe your commuter train habits closely, you may even notice yourself imitating the actions of the others around you. This is the result of “isopraxism” - when all the individuals in a group try to behave in the same way to avoid bringing the focus onto themselves and thus putting themselves in danger.
We may well get nervous as we bump along in our commuter trains, crammed into the armpit of the person next to us. But this feeling ought to pale in comparison to the anxiety felt by the Japanese on their way to work.
During rush-hour, Tokyo’s carriages are on average filled to 200 per cent their capacity, compared with 150 per cent on the very worst Tube trains in London.
In fact, the crush-loading in Japan is so intense that since the sixties Japanese rail operators have employed oshivas, or “pushers”, to shove passengers onto trains so not even a centimetre of space remains between them.