A MAN walks confidently towards an open gate but instead of going straight through he raises his knee very high as if he were stepping over a low wall. He strides forward, reaching out to shake a friend’s hand. But again he misjudges, and his friend draws back in alarm to avoid being punched in the nose…

This article was first published in New Scientist on 11 October 2014. To continue reading, click here (paywall).