METACOGNITION, ILLUSORY SUPERIORITY EFFECT, DUNNING-KRUGER EFFECT, SUPERIORITY COMPLEX and INFERIORITY COMPLEX
We all think but not all of us can think about we think. We all know things but not all of us can know what we know. We all remember things but not all of us can remember what we remember. The ability to think about what you think, know what you know, and remember what you remember is called METACOGNITION. It is like a two-storeyed building. Almost everybody can climb from the ground floor to the first floor and see what's below (that is "think", "know", and "remember"). However not everybody can climb higher to the second floor to view what's on the first floor beneath (that is, think about and be in charge of what they think, realize what they know, and remember what they can remember). Metacogntion is better referred to as "self-awareness".
The ILLUSORY SUPERIORITY EFFECT is tendency for people to think they are more intelligent and better than others. They see themselves as superior to others when in reality they are not. We say they're suffering from "mega". Scientists refer to this as the illusory superior effect which is due to lack of metacognition. It is because they are not intelligent enough to assess how intelligent they truly are. It takes some intelligence (metacognition) to be able to truly know how intelligent one is.
Nobody wants to be seen as stupid. So there's a tendency for everybody to say they are smart even when they are not. However there is a difference. Normal people will know that they are not smart but may still say they are smart. They know the truth about themselves; they're only trying to preserve their self-esteem and they will most likely not say they're smarter than everybody else. On the other hand, people who are suffering from the illusory superiority effect can't even realize that they are not smart. So when they say they're smarter than everybody, they truly mean it even though they're wrong.
DUNNING-KRUGER EFFECT is the tendency of unintelligent people to think they are intelligent and the tendency of intelligent people to think they are less intelligent than others. For stupid people who think they're smart, it's because they lack awareness of their own abilities (lack of metacognition), similar to the illusory superiority effect. For smart people who think they're less intelligent than others, it's because they lack awareness of the abilities of others and thus overrate the ability of others relative to theirs. It might also be because the more someone knows, the more they think they don't know. Intelligent people suffering from Dunning-Kruger effect may be seen as humble by people around them.
Don't confuse these with the complexes.
SUPERIORITY COMPLEX is a collection of behaviours that emanate from an individual's perception that they are superior to others. Because they feel they're superior to others (exagerrated self-esteem), they feel no pressure to impress people. They don't care about what others think about them neither do they listen to other people. Why? Because they think they're superior. They are not interested in making you like them. They're not interested in people's acceptance. They don't mind being assholes as their feeling of supremacy is internal. They don't care whether people see them as good or bad, intelligent or dumb, ugly or beautiful. We're social animals who derive some esteem from others. People who suffer from superiority complex don't care about this and thus they manifest anti-social behaviours.
INFERIORITY COMPLEX, on the other hand, is a collection of behaviours that emanate from an individual's perception that they are inferior to others. Directly opposite to superiority complex. They feel they're inferior to others and thus need to impress to meet up. To compensate for their low self-esteem, they over-stretch themselves in everything to be seen as measuring up. Many high achievers in life today achieved so much because they suffered from inferiority complex.