Surprising or contradictory health news stories encourage readers to be sceptical about science

The Kill or Cure website monitors the Daily Mail's attempt to "classify every inanimate object into those that cause cancer and those that prevent it". Like many other media outlets, the Mail is drawn to health news that is contradictory and/or surprising and a perusal of the Kill or Cure website shows that the paper has frequently reported that the same items, such as aspirin or beer, both cause and prevent cancer.

Now a study published recently in Science Communication examines the impact of such stories and finds that they have a negative influence, provoking readers to distrust the stories themselves and also, more worryingly, their ultimate source – science.

Chingching Chang at National Chengchi University in Taiwan asked 200 students to read real health news stories that were either low or high in novelty (e.g. about how "green tea reduces bad cholesterol" or that "popcorn slows down ageing"); or one-sided (e.g. milk prevents cancer) or contradictory (e.g. milk both causes and prevents cancer).

Students who read novel or contradictory findings rated the news itself as less credible, had lower intentions to act on it, felt more uncertain, and reported more negative attitudes towards scientific health research in general, as compared with the students who read about unsurprising or one-sided health findings. Chang says this fits what we know about "motivated reasoning" – people don't like feeling uncertain and so they will often respond to unsettling or confusing new information by doubting its credibility.

This general pattern of results was similar when Chang conducted a telephone survey of hundreds of members of the public, asking them to respond to health story headlines that were novel versus unsurprising, or one-sided versus contradictory.

On a positive note, the students who were exposed to either novel or contradictory stories still expressed levels of credulity and attitudes towards health research that were relatively positive on the rating scales that were used (albeit that they were notably more negative than the ratings given by the students exposed to low-novelty and one-sided stories).

Health journalists' bias for surprising and contradictory findings (perpetuated in part by the work of university press offices), is to some extent understandable – it helps add drama and increases reader interest. But unless the novel/contradictory findings are placed in context and include appropriate caveats, Chang warned that her findings suggest such stories can "leave people uncertain about scientific health research, and breed negative attitudes toward science and research overall." Chang also advises news outlets to avoid "false balance", in which "conflicting evidence with less support appears alongside evidence with overwhelming support."

Further reading

Chang, C. (2015). Motivated Processing: How People Perceive News Covering Novel or Contradictory Health Research Findings Science Communication DOI: 10.1177/1075547015597914