Research among smokers in New England showed that when smokers saw “non-smoking” signs they thought about wanting to smoke as the idea was put into their heads – even though they may not have consciously noticed the sign.
This is not news for anybody who has been told “don’t think of a purple elephant” who then of course has that image in their head.
It seems the brain has to process what it is you are not supposed to be doing and doesn’t seem very efficient about handling negative statements. (So parents don’t tell your kids what they shouldn’t be doing but what they should, and managers give your staff objectives which are positive not negative).
A researcher from Oxford University makes the point that many Public Health campaigns are telling people what they shouldn’t be doing and this may have the opposite effect.
Source: BPS Annual Conference.