“Mood evidently affects the operation of System 1: when we are uncomfortable and unhappy, we lose touch with our intuition. These findings add to the growing evidence that good mood, intuition, creativity, gullibility, and increased reliance on System 1 form a cluster. At the other pole, sadness, vigilance, suspicion, an analytic approach, and increased effort also go together. A happy mood loosens the control of System 2 over performance: when in a good mood, people become more intuitive and more creative but also less vigilant and more prone to logical errors.”

“This is the essence of intuitive heuristics: when faced with a difficult question, we often answer an easier one instead, usually without noticing the substitution.”

“Intelligence is not only the ability to reason; it is also the ability to find relevant material in memory and to deploy attention when needed.”

“We tend to match the emotions of those around us. For example, we’re more prone to become stressed when we’re around someone who is high-strung. And we’re more likely to be in a good mood when others around us are laughing.”

“Freedom is only to be found where there is burden to be shouldered. In creative achievements this burden always represents an imperative and a need that weighs heavily upon man’s mood, so that he comes to be in a mood of melancholy. All creative action resides in a mood of melancholy, whether we are clearly aware of the fact or not, whether we speak at length about it or not. All creative action resides in a mood of melancholy, but this is not to say that everyone in a melancholy mood is creative.”

“What we firmly believe, if it is true, is called knowledge, provided it is either intuitive or inferred (logically or psychologically) from intuitive knowledge from which it follows logically. What we firmly believe, if it is not true, is called error. What we firmly believe, if it is neither knowledge nor error, and also what we believe hesitatingly, because it is, or is derived from, something which has not the highest degree of self-evidence, may be called probable opinion. Thus the greater part of what would commonly pass as knowledge is more or less probable opinion.”

“A general “law of least effort” applies to cognitive as well as physicalexertion. The law asserts that if there are several ways of achieving thesame goal, people will eventually gravitate to the least demanding courseof action. In the economy of action, effort is a cost, and the acquisition ofskill is driven by the balance of benefits and costs. Laziness is built deep into our nature.”