"WHAT SCIENTIFIC CONCEPT WOULD IMPROVE EVERYBODY'S COGNITIVE TOOLKIT?"
This is a wonderful question and I look forward to the answers, many of which may also be wonderful, even though I may end up burdened with as many as 158 concepts.
(Note the linked page is quite a godawful mess, web-designically speaking. Scroll down to "BEGIN READING HERE" when you are ready to start reading...)
However, judging by the 158 titles, they should have asked me, because the one I would propose appears to be missing. So, before I go exploring the other 158, here's my contribution.
At first glance, there's a fundamental problem with science as a method. On the one hand, one is expected to take nothing on faith, to doubt everything, never to defer to authority. On the other hand, science is obviously a cumulative business. By now millions of person-years have been amassed, and it would seem to be impossible, to long have been impossible, to replicate enough of that thinking to get to the cutting edge where knowledge could be advanced.
In practice this presents no problems. We base our work on "established science". But how is this possible when we take nothing on faith? We pretend it is by reference to the "peer reviewed literature" but that is something of a pose. Reviewers are insufficiently rewarded to provide the requisite review. The system is there to make a plausible claim for a good-faith effort. It doesn't actually provide effective gatekeeping, and many trivial or incorrect results are published. Consequently the literature is really not enough. (*) But obviously science does work.
The undercelebrated key to science is coherence. The facts and methods that work in any discipline are the ones that "make sense" in the context of all the other facts and methods. Outsiders coming in and offering ideas generally fall outside the established context. The experienced scientist's first reaction is "no, that can't be true", followed by identification of a contradiction with a well-known bit of reality. That is, the wrong idea is incoherent with established knowledge.
Ideas that fall into "hey that might be true" are dramatically rarer, especially if they have a soupcon of "and that would explain this other thing that has been bugging me, too". And those are the ones to which we need to apply the full brunt of our skepticism, the ones that might survive into the shared network of coherence. So, our ability to advance the truth is based fundamentally on our understanding the truth well enough to quickly discard most untruths. Constructing a realistic and productive perspective is a matter, like the sculptor removing all the marble that is not part of his subject, of getting good at throwing away the stuff that doesn't matter. The stuff that doesn't matter is the stuff that is incoherent with what is already known.
(*) Highlighted text used to say: We pretend it is by reference to the "peer reviewed literature" but everyone knows that much of what passes peer review, probably a majority, is nonsense published for the benefit of tenure committees and grant reviewers. The literature is no help.
It's been argued that this is too strong and in retrospect I agree.