Tyler Cowen often inveighs against the Fallacy of Mood Affiliation:

It seems to me that people are first
choosing a mood or attitude, and then finding the disparate views which match
to that mood and, to themselves, justifying those views by the mood.  I
call this the “fallacy of mood affiliation,” and it is one of the most underreported
fallacies in human reasoning.  (In the context of economic growth debates,
the underlying mood is often “optimism” or “pessimism” per se and then a bunch
of ought-to-be-independent views fall out from the chosen mood.)

Mood affiliation is indeed a pervasive intellectual problem.  But Tyler misses half the story.  Yes, the desire to feel any specific mood can lead people into error.  At the same time, however, some moods are symptoms of error, and others are symptoms of accuracy. 

When someone expresses his views with a calm mood, you consider him more reliable than when he expresses his views with an hysterical mood.  We give more credence to someone who discusses alleged war crimes somberly than if he does so flippantly.  As far as I can tell, this is justified.  One of the main reasons I’ve never bothered to investigate Holocaust denial is that the Holocaust deniers I’ve encountered think that genocide is hilarious. 

Now consider my favorite passage from Alex Epstein‘s The Moral Case for Fossil Fuels:

[A] proper reaction to a major danger from fossil fuels would be sorrow. Think about it: If
the energy that runs our civilization has a tragic flaw, that is a
terribly sad thing. It would be even worse, say, than if wireless
technology caused brain cancer. The appropriate attitude would be
gratitude toward the fossil fuel companies for what they had done for
us, combined with recognition that we would have to suffer a lot in the
years ahead, combined with the commitment to the best technologies that I
mentioned earlier [hydro and nuclear].

While Tyler might accuse Epstein of fallacious mood affiliation, Epstein makes a deep point.  Namely: A reasonable person who was convinced that fossil fuels posed a major danger would feel a specific package of moods:

1. Sadness that a crucial resource has terrible side effects.

2. Gratitude for all the wonders the resource brought us in the past.

3. Resignation that mankind must forego many of these wonders.

4. Determination to salvage as many wonders as possible by using the best available substitutes for fossil fuels.

When an opponent of fossil fuels evinces none of these moods, it strongly suggests he isn’t reasonable.  It doesn’t mean he’s wrong, but we should definitely be suspicious of whatever comes out of his mouth.  If virtually every opponent of fossil fuels lacks these moods, similarly, it strongly suggests that the whole movement is unreasonable.  It doesn’t mean the movement’s wrong, but we should definitely be suspicious of its central tenets.  The same goes for any other position: You can learn a lot by comparing the mood reasonable proponents would hold to the mood actual proponents do hold.

Of course, if you have the expertise and time to directly evaluate someone’s claims, you don’t need to use their moods to triangulate their credibility.  Then you’d just review the facts and forget the moods.  Otherwise, though, mood is a valuable clue.  Appropriate mood suggests credibility.  Credibility suggests truth.  It’s a fallible heuristic, but we all use it and we’re wise to do so.

Question: What’s the best relevant psychological research on the correlation between mood and accuracy?