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 example, sailors wearing life jackets may try more risky maneuvers as they feel ‘safer’ if they get into trouble. If they weren’t wearing life jackets, they might not even try. So despite the ‘safety measures’ the overall level of risk remains the same due to behavioural change.
This happens in other areas of life. Known as self-licensing it is where people will allow themselves to indulge in more harmful behaviour after doing something ‘good’.
For example, people who take health supplements are more likely to engage in unhealthy behaviours as a result.
The moral of the story, of course, is to stay in the bunker.
Link to BMJ editorial ‘Bicycle helmets and the law’.