It’s an old debate. Should you ‘accentuate the positive; eliminate the negative’ or give them a reality check by telling them how serious things could be if they don’t accept your argument? It depends on their starting point. Philip Broemer of the University of Tubingen in Germany believes that the key issue is ambivalence.
If your audience is likely to have conflicting feelings about your cause, consider the negative argument. Broemer tested negative messages in a study that promoted exercise and a low fat diet to reduce the risk of heart disease. Most people are ambivalent about exercise and diet and the study suggested that emphasizing the dangers of not changing our lifestyle is more effective than telling us how we will benefit. He found that people who were ambivalent about using condoms to prevent HIV were much more often persuaded by messages about the dangers of unprotected sex than assurances that they would feel much safer if they used them.
Earlier research suggests that our perception of risk is a significant issue too and it’s clearly a factor in our ambivalence.
Positive messages, telling us how we’ll benefit, work best if we think the risk is low or non-existent. There’s no great risk, for most of us anyway, in walking to work, so use a positive message - say, ‘Walk to work and you’ll keep fit and healthy and save a fortune in transport'. It should be more effective than the negative, ‘Walk to work or you’ll lose your fitness, get sick more often and lose a fortune in transport’.
Effective persuaders can’t assume that the natural human motivation to protect ourselves from harm is enough to change our behaviour. We need to show people that there is a real danger and that they are personally vulnerable. We also need to convince them that the action we are suggesting will help them avoid danger and that it’s practical for them to take that action. We may need a series of messages targeted at those four issues.