Motivated reasoning is the process by which we reach the conclusion we wanted and then construct the justification, while sincerely experiencing it as objective analysis. The uncomfortable finding from decades of research is that being smarter doesn't protect against it — it makes it worse, because greater analytical ability means a greater capacity to generate plausible-sounding reasons for what you already believed.
The tell is asymmetric scrutiny. When evidence supports what we want, we ask 'can I believe this?' and accept it readily. When it contradicts us, we ask 'must I believe this?' and hunt for flaws — and there are always flaws, in every study. Same person, same standards nominally, completely different thresholds. The only reliable defense isn't more intelligence; it's structural: seeking out disconfirming evidence deliberately, committing to what would change your mind before seeing the data, and exposing your reasoning to people who want to find its errors.