What scientific concept would improve everybody's cognitive toolkit?

"Everybody" is a tricky feat, especially with personal variations in acuity and all the bizarre pressures pleading for the plebians to make a sole contribution to science in the form of trust or faith. But perhaps healthy humility, ability to Not-understand patiently enough to avoid dogma, a natural or cultivated respect for objectivity, a rugged tolerance for ugly truths, and as counterintuitive and unscientific as it may seem yet most important of any cognitive factor in my view, kindness -- you can try a 'for those who deserve it' approach, but one must be extraordinary to accomplish it without much error. If kindness proves impossible, critical thinking may compensate. Blend them to become a really cool human.

That's probably a bunch of shit, though it makes sense to me despite my deficiencies, which is possibly why I'm not a scientist™, but not incognizant.

Edit to contradict myself: I also think we need a prudent fear of ourselves, individually and foremost, collectively. Not caustic cynicism, but sober trepidation.

Negativity bias[0]

Bad stuff stands out more than good stuff for reasons baked in by natural selection.

It doesn't mean their aren't genuienly bad things but we tend to weight them more heavily than we need to.

If I make a suggestion in a meeting and 9 people say it's a good idea and one person says it's a terrible idea my tendency will be to focus on the 1 negative reaction.

That doesn't mean you want to ignore negative stuff (maybe that negative reaction is correct). I just try to keep negativity bias in mind and ask myself if something is really as bad as it seems or if it might be playing a role.

The place this is most obvious to me is in news and social networks. I think negativity bias is a large part of why depressing or hopeless headlines spread much more effectively than positive ones.

[0] https://en.m.wikipedia.org/wiki/Negativity_bias

That there's a lot we don't know. That even things with substantial evidence can be considered theories and not laws.

That we should try to attack our own hypotheses to make sure they do not contain flaws. That attempting to disprove our position can potentially produce the strongest support of it.

On the other side, there are some things to avoid. Science is not a religion, nor is it policy (policy should be built off of the science and society's input, but shouldn't implicitly be used as policy).