A couple of years ago Solomon Hsiang, assistant professor of public policy at University of California, Berkeley and co-director of the Lab, became fascinated by an important issue: what effect does heat have on our brains – and emotions? It is a pertinent question right now, given that temperatures have soared this summer across most of Europe and the US – currently, some 70 million Americans are still under some level of “heat advisory” notice. Hsiang and his research team wanted to know whether there is something about hot weather that destabilises our brain and makes us violent. This is not a new issue: a recent meta-analysis of 60 prior studies showed that unstable temperatures tend to be correlated with conflict.