"A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses." - Carlo M. Cipolla
I’ve noticed several things about stupid people: they are impulsive in speech and behavior, and they do not learn from their experience. They don’t know they’re stupid, and instead think they’re pretty smart. They overestimate their competence to the point they can't even tell if they are incompetent. In other words, they're confident - and it is unwarranted.
I am reminded of the novel, A Perfect Crime, in which the criminal is described as looking, "confident, crafty and stupid."
The stupid give bad advice but never listen to good advice. They very often think other people are the cause their problems.
Stupidity, then, is a character flaw.
The stupid also tend to be extroverts. Introverts, if they are extremely introverted, can end up isolated and eccentric – what is called schizoid – but when it comes to stupidity and crime, extroversion is associated with it.
The impulsive lack the ability to reflect, to contemplate. They lack self-knowledge, since they don’t think about their flaws. To the extent they do think about themselves, it’s about what people have done to them, and not what they’ve done to people. They lack empathy.
They can't see into the future. They can't imagine the consequences of their actions. They always think in the short term.
The smartest people learn from other people's mistakes. The less intelligent, i.e., the average person, can learn from their own. The dumbest people can't even learn from their own mistakes.
The mean average IQ of prisoners is 93. They end up in prison not only because they're stupid, but also because they're impulsive and don't learn from their own mistakes. I once saw a prisoner on TV who ran from the cops in a stolen Corvette and ended up totaling it. He said during the entire chase it "never occurred to me what might happen."
The stupid are very sensitive to what they think people have done to them, but almost clueless about what they’ve done to others, even if it’s obvious they’re not acting as they should toward others. They have a blind spot.
Impulsiveness and not learning from their mistakes is obviously what lands people in prison. “I didn’t think about what would happen,” they tell authorities. It’s an old story, one of the oldest there is.