I think the argument above is that the instrumental rationalist might decide not to become an epistemic rationalist? If the 'winners' (say, 'happy people' or 'productive people') tend to believe in a load of codswallop, then should I attempt to brainwash myself to believe the same?
then should I attempt to brainwash myself to believe the same?
No. You should find out what value it is that they get from that, and do the optimal thing to get that value.
Think for analogy of pulling the bayes structure out of a neural network or something. Once you know how it works, you can do better.
Likewise with this; once you know why these particular bad beliefs have high instrumental value, you can optimise for that without the downsides of those particular beliefs.
Taylor & Brown (1988) argued that several kinds of irrationality are good for you — for example that overconfidence, including the planning fallacy, protects you from depression and gives you greater motivation because your expectancy of success is higher.
One can imagine other examples. Perhaps the sunk cost fallacy is useful because without it you're prone to switch projects as soon as a higher-value project comes along, leaving an ever-growing heap of abandoned projects behind you.
This may be one reason that many people's lives aren't much improved by rationality training. Perhaps the benefits of having more accurate models of the world and making better decisions are swamped by the negative effects of losing out on the benefits of overconfidence and the sunk costs fallacy and other "positive illusions." Yes, I read "Less Wrong Probably Doesn't Cause Akrasia," but there were too many methodological weaknesses to give that study much weight, I think.
Others have argued against Taylor & Brown's conclusion, and at least one recent study suggests that biases are not inherently positive or negative for mental health and motivation because the effect depends on the context in which they occur. There seems to be no expert consensus on the matter.
(Inspired by a conversation with Louie.)