Degrees of freedom
Writing on behalf of BBC Future, Zaria Gorvett asks whether hot weather can increase crime rates.
There certainly seems to be a wealth of information supporting a correlation between higher temperatures and violent behaviour. But patterns are only patterns; associations are not proof of dependence; and correlation does not imply causation, as any epidemiologist will tell you.*
To her credit, Gorvett recognises and acknowledges these limitations herself:
An important consideration is that most of these studies are based on correlation – they link one factor, temperature, with another, crime. But this doesn’t mean one necessarily affects the other directly. When the Sun comes out, we inhabit a very different world – one of partying at crowded festivals, socially acceptable daytime drinking, and generally being more active. Could these summer activities, which bring us into contact with other people and heighten our emotions, be the real drivers behind our heatwave behaviour?
Zaria Gorvett, The troubling ways a heatwave can warp your mind, BBC Future
There's also the possible detrimental effect that heat has on sleep patterns, and therefore on mood; less sleep, more grumpy. So, all in all, definitely quite interesting.
But I was irritated by the lack of the degree symbol throughout her article, an irritation that was probably exacerbated by the August temperatures. Really, 25C should only be used in place of 25°C by cretins and in TXT MSG SPK, and even then only because there's no ° symbol in the first place. Not that anyone would use it anyway! (grumpy)
I'm not so sure that I'd accept the Greek study that she cites at face value, since it has some methodological deficiencies and appears to have been published
in an open access comic. Given the balance of supporting information, however, I'll let that pass.
* Tyler Vigen has compiled a collection of spurious year-by-year correlations, including:
- US spending on science, space, and technology correlates with suicides by hanging, strangulation, and suffocation;
- per capita cheese consumption correlates with the number of people who died by becoming entangled in their bedsheets;
- divorce rate in Maine correlates with per capita margarine consumption;
- and, per capita mozarella cheese consumtion correlates with the number of civil engineering doctorates awarded.