Effects of Positive Language and Profession on Trustworthiness and Credibility in Online Health Advice: Experimental Study

BACKGROUND: When searching for health information, many people use the internet as their first source of information. In online health forums, for example, users post their questions and exchange health advice. In recent years, information givers from various professions have begun to use positive language (indicated by the frequent use of positively valenced adjectives) to communicate their information and persuade their audiences. OBJECTIVE: The goal of the current study was to answer the following research questions: (1) How does positive language, in comparison to neutral language, influence the trustworthiness of a person arguing in an online health forum and the credibility of their health claims; (2) How does working for a university, compared to working for a lobbying organization, influence the trustworthiness of a person arguing in an online health forum and the credibility of their health claims; and (3) Do the two factors of language style and professional affiliation interact with each other to influence trustworthiness and credibility judgments? METHODS: In a 2 × 2 between-subject experiment, 242 participants read a post from an online health forum and subsequently rated the trustworthiness of the forum post author and the credibility of their information. Within the post, the professional affiliation (scientist vs lobbyist) and language style (neutral vs positive) of the forum post author was varied. RESULTS: When the forum post author used a positive language style, they were perceived as less trustworthy (high Machiavellianism [P<.001; η(2)(p)=.076], low Integrity [P=.001; η(2)(p)=.045], and low Benevolence [P=.02; η(2)(p)=.025]) and their information was perceived as less credible (low Message Credibility [P=.001; η(2)(p)=.045]). The professional affiliation of the forum post author did not influence their trustworthiness or the credibility of their information. CONCLUSIONS: When searching for health information, information seekers evaluate the language style of forum posts to decide whether forum post authors are trustworthy and their information is credible.