You can't scare people into getting fit or going green

Recent years have seen increasing efforts to encourage people to do more for their health and for the environment, for example by recycling more, using cars less and taking more exercise. But what messages have been successful, and why?

Theories have long suggested that by changing attitude, social rules and people's own ability to reach their goals, people’s intentions or decisions to act in a particular fashion will be changed, which in turn determines the extent of change in behaviour. But the supporting evidence for these widely accepted ideas was weak; there was a need to take a closer look at experiments that changed attitudes, norms and self-efficacy in order to measure the true extent of any changes in subsequent intentions and behaviour.

The research project, ‘Does changing attitudes, norms or self-efficacy change intentions and behaviour?’, led by Professor Paschal Sheeran of Sheffield University, provides the crucial missing evidence about the role of these three factors in behaviour change by reviewing all the successful experiments in the past 25 years and quantifying their effects on decisions and actions.

The team identified 33 distinct strategies for changing intentions and behaviour across the 129 different studies. The most frequently used strategies provided general information, details of consequences and opportunities for comparison. Yet the most effective strategies were to prompt practice, set specific goals, generate self-talk, agree a behavioural contract and prompt review of behavioural goals. The two least effective strategies involved arousing fear and causing people to regret if they acted in a particular fashion.

They also examined whether the characteristics of a particular study influenced how well changes in attitude, social norm and self-efficacy influenced intentions and behaviour. There was little evidence that the way factors were measured influenced the findings, though studies that used students or had short follow-up had stronger effect on intentions.

The team’s findings show that changing attitude, social norms and behaviour succeeds in making a statistically noticeable difference in people’s intentions and behaviour about 60 per cent of the time. The team found the amount of change in intentions and behaviour to be ‘meaningful’ and of ‘medium’ size according to standard procedures for describing effect sizes.