Perhaps the most interesting psychological bias I have thought about recently is the Dunning-Kruger effect. You can read the Wikipedia summary here, but to crudely summarize it: unskilled people think they are highly skilled, while skilled people think they have no special skills. Counterintuitive, right?
Self-assessments are a fascinating paradox. The ability to accurately judge one’s own proficiency and skill is trickier than you think, thanks in large part to the Dunning-Kruger effect. The phrase “objective” is commonly applied to self-assessment as though it simply requires a conscious effort to achieve. “I’m going to be very objective about myself” is an admirable statement of intent, but in many cases fails to live up to those aspirations. Not for lack of trying, but game is rigged against us.
Yet, at least in American culture we so highly prize the right to self-determination that we see self-assessments as a laudable aspect of skill evaluation. And while there may be merit to the psychological process of self-evaluation (expressing thoughts, thinking out loud, etc), the accuracy of that self evaluation is certainly questionable.
The fascinating and frustrating part of the Dunning-Kruger effect is that there’s not really any way to inoculate oneself from its effects. If you’re highly skilled but don’t know it, you can’t compensate by over-estimating your abilities. The same goes for the unskilled – you can’t compensate for something you don’t know. This type of bias is structural to human psychology, and not easily rooted out.
If anything, knowledge and awareness of the Dunning-Kruger effect’s very existence is about the best thing I can think of to ward off the negative impact within one’s limited ability. And it may not help make self-assessment any more accurate than before. But at least when someone asks you to complete a self-assessment, you can take the result with a big ol’ grain of salt.