The British Medical Journal has a fascinating editorial on the behavioural complexities behind the question of whether cycling helmets prevent head injuries.
You would think that testing whether helmets prevent bikers from head injury would be a fairly straightforward affair. Maybe putting a bike helmet on a crash test dummy and throwing rocks at its head. Or counting how many cyclists with head injuries were wearing head protection – but it turns out to be far more complicated.
The piece by epidemiologist Ben Goldacre and risk scientist David Spiegelhalter examines why the social and behavioural effects of wearing a helmet, or being required to wear one by law, can often outweigh the protective effects of having padding around your head.
People who are forced by legislation to wear a bicycle helmet, meanwhile, may be different again. Firstly, they may not wear the helmet correctly, seeking only to comply with the law and avoid a fine. Secondly, their behaviour may change as a consequence of wearing a helmet through “risk compensation,” a phenomenon that has been documented in many fields. One study — albeit with a single author and subject—suggests that drivers give larger clearance to cyclists without a helmet.
Risk compensation is an interesting effect where increasing safety measures will lead people to engage in more risky behaviours.
For the rest of the story: http://mindhacks.com/2013/06/13/protect-your-head-the-world-is-complex/