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from the character-assassination-for-dummies dept.
Argumentum ad hominem, a well-known fallacy that involves attacking the character or motive of the person making the argument rather than arguing their claims on their merits, is frequently encountered, and despite being fallacious, it is disturbingly effective. A new study in PLOS One (open, DOI: 10.1371/journal.pone.0192025) sheds some further light on just how effective the various types of ad hominem attacks are in the context of scientific claims. An article from Psypost reports on the findings:
Ad hominem arguments — attacking a person to disprove his or her claims — is considered a logical fallacy. But a new study published in PLOS One suggests that some ad hominem attacks can effectively erode people's trust in scientific claims.
The research found that attacking the motives of scientists undermines the belief in a scientific claim just as much as attacking the science itself.
[...] "One key finding is that if members of the general public are aware of a conflict of interest connected to a scientific finding, then this will seriously undermine their faith in that finding," Barnes told PsyPost. "What the study does is allow us to quantitatively compare the amount of attitude change based on knowledge of conflict of interest to the amount of attitude change based on knowledge of outright research fraud and misconduct (such as faking the data)."
"What we see is that knowledge of conflict of interest is just as powerful as knowledge of research fraud."
Further commentary on the study by Orac at Respectful Insolence.
(Score: 2) by stormwyrm on Saturday February 17 2018, @12:41AM
Much more important than the credibility of the authority is whether the authority is even relevant. This is the key difference between a valid ad verecundiam and a fallacious ad verecundiam. BK might be a scientist, but what sort of scientist is he? He could be a geologist, in which case his authority is completely irrelevant to what colour the sky is, since his speciality is looking at the ground rather than the sky, and in rocks rather than light. On the other hand, if he were a physicist who was trained in quantum electrodynamics and spectroscopy, that would make his conclusions more probably true, since his speciality is light and its interaction with matter, which is absolutely relevant to the question of the sky's colour. But (and this is important) only more probably true. A valid ad verecundiam is a Bayesian rather than strictly logical argument. But if then you got a lot of similarly qualified authorities and they all mostly said the same thing, the probability that they might all be wrong becomes very small indeed.
Examining conflict of interest is the same. It is also a Bayesian argument. If someone making a study has a conflict of interest, it only makes what they say suspect (i.e. more likely to be false) rather than strictly false, the way a strictly logical argument would. Just because someone is biased doesn't make them wrong. The only solution, as with the problem of arguments from authority, would be to look for further data from less biased sources. If other, less biased sources then also come to the same conclusion as the biased one, is the biased source wrong? Of course not.
Numquam ponenda est pluralitas sine necessitate.