In the 1960s, Howard Leventhal, a social psychologist at Yale University, undertook an experiment to see if he could change students’ behaviours.

At the time, the University Health Centre was supplying free tetanus vaccinations. Leventhal wondered how he could influence senior students to get the vaccination.

Leventhal made two booklets. Both booklets contained the same information about the vaccination, but one was a low-fear version and the other a high-fear version. The low-fear version had a dispassionate description of the disease. The high-fear version had dramatic descriptions of the ramifications of not getting a vaccination and included graphic pictures of urinal catheters and tracheotomy scars. Half of the students received the low-fear version and the other half received the high-fear version.

The students filled in a questionnaire after reading the booklet. They all had a good understanding of what tetanus is, but the real test was whether they would get vaccinated.

After one month, only 3% of participating students were vaccinated.

Leventhal wondered if he had done something incorrectly, so he had the experiment validated by other academics. They confirmed nothing was wrong with the experiment.

Leventhal wanted to try it again. He used the same booklets but made one slight change. Both booklets had an additional page added with a map of the campus and a circle around the health centre. Also clearly marked were the times that the centre was open for vaccinations.

A month later, 28% of participating students had received their tetanus vaccination—an eight-fold increase.

Leventhal was looking to see whether fear influenced behaviour change. Ultimately, he found that it didn’t make a difference—the number of participants who had received vaccinations were split 50/50 between the high-fear and low-fear booklets.