Evident or doubtful? How lexical hints in written information influence laypersons' understanding of influenza.

There are clear differences in the way written information on health issues presents research findings. In some cases, the source of a piece of information (e.g. "expert professor") is highlighted to emphasize its credibility and relevance. In other cases, the impact of a certain argument is stressed by avoiding hints on tentativeness such as "mostly" or "up to now." This article examines whether and how far such differences influence laypersons' comprehension of the contents provided. In an experimental setting, 157 laypersons were asked to read an online article on a new approach to preventing influenza. The texts manipulated whether there were (a) hints on the source of information and (b) lexical hints on the tentativeness of the information (hedges). After reading the text, participants were asked to write an essay reporting their opinion on the topic. Their argumentation on vaccination was assessed with content analysis and their attitudes toward vaccination were surveyed with a questionnaire. Results indicated that when lexical hints were given, tentativeness led participants to focus more on the actual information in the text. Additionally, decisions more strongly favored the direction implied in the text when the source of the medical information was not reported. Consequences for the way health information should be presented to laypersons are discussed.