Letters: What cycle helmets can tell us about face masks

Masking the truth

Sir: Matthew Parris is right to laud the importance of embracing the scientific method (‘Why should opinion matter more than science?’, 25 July) to determine the efficacy of face masks. However, his proposed experiment contains a significant oversight — the human factor. That is, how the very wearing of a mask (or a conscious decision not to) may itself result in behaviours that alter transmission risk.

Multiple studies into the benefit of wearing a bicycle helmet provide a useful reference. Those forced to wear one by law may do so incorrectly simply to avoid a penalty. Meanwhile they may also indulge in ‘risk compensation’ — more dangerous cycling because they feel safer.

These factors are near impossible to replicate in a laboratory-based study and so the epidemiological ‘experiment’ in which we are all currently engaged may in fact provide insight equally essential to future policy-making.
Paul Bradley
London NW5