If you claim you’re a doctor online, even without providing any proof, people may trust you more than the CDC. A new study has found that online comments have as much power as statements issues by health institutions – and in some cases, even more.

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In the wake of the recent measles outbreak in California and with more outbreaks lurking on the horizon, it’s become clear that we need to encourage and promote vaccination even more than we’re doing now. But we also need to figure out why the message isn’t sinking in – why people choose to ignore scientific recommendations and believe in something else.

A new study may in the Journal of Advertising found that something as simple as internet commenting can sway public opinion just as much (or more) as public service announcements (PSAs) from health authorities. The key here is neutrality; people believe comments because they see them as coming from an unbiased source, whereas PSAs may follow an agenda. If the one doing the comment claims he’s a doctor, that gives his statement even more power, even though he’s not providing any proof.

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“Findings indicate that online commenters who are perceived to be credible are instrumental in influencing consumers’ responses to pro- vs. anti-vaccination online PSAs. Results further suggest that it is not the advertising message (i.e., the PSA advocated position) alone that influences consumers’ responses (even when consumers perceive the PSA sponsor to be highly credible) but rather, the commenters’ reactions to the claims presented in the PSA that also independently contribute to consumers’ vaccination attitudes and behavioral intentions. Finally, results also show that when the relevant expertise of online commenters is identified, the effectiveness of the PSA’s advertising message is moderated by the interactive effect of the online comments and their associated perceived credibility”, researchers write in the paper.

In order to find this, researchers recruited 219 adults from Amazon’s Mechanical Turk and asked them to view either a pro-vaccination or anti-vaccination PSA. The participants were led to believe that the pro-vax message was sponsored by the Centers for Disease Control and Prevention (CDC) and the anti-vax message sponsored by the National Vaccine Information Center (NVIC). A pretest ensured that both agencies have equal initial credibility. Each PSA was designed to look as if it appeared on a website, and was followed by four comments – either agreeing or disagreeing with the statement (the name of the commenters was neutral, so that gender bias was avoided). Then, participants were asked to fill in a survey regarding their attitudes toward vaccinating themselves and their families. They were also asked to rate the credibility of both the PSAs and commenters. Also, after the study was done, all participants were debriefed regarding the lack of validity of the statements, so that no harm was done to vaccination efforts.

For the first participants, the commenters had no additional information regarding their identity; the researchers then repeated the setting, but added more information for the commenters – they were either a doctor of infectious diseases and vaccinology, a lobbyist specializing in healthcare issues, or an undergraduate student in English literature.

The results were quite surprising. First of all, the comments had almost as much impact as the PSA, and when the commenter was viewed as more credible (as with the “doctor”), comments were even stronger than the PSA itself.

The results are disconcerting. This means that internet manipulation is so incredibly easy to conduct – all you have to do is write comments that seem valid. It also highlights a devastatingly weak point of public health campaigns and science communication in general – the lack of credibility. The fact that an anonymous claiming to be a doctor has more credibility than actual doctors seems bizarre, and likely indicates a lack of credibility of public bodies.

This also seems to indicate why opinions on issues such as climate change are so split up, despite the overwhelming scientific evidence (1, 2, 3, 4, 5, 6) – people trust random, often unqualified people over the specialists. I guess the solution isn’t to stop looking at comments or non-scientific debates, but rather to dig deeper and find the actual information for yourself.

Journal Reference: Ioannis Kareklas, Darrel D. Muehling, T. J. Weber. Reexamining Health Messages in the Digital Age: A Fresh Look at Source Credibility Effects. DOI: not available yet.