For a bit of context, the good Dr. Thompson, on his excellent blog, gives a brief summary of the most important things to know about intelligence (emphasis added):
Intelligence does not guarantee good decision-making in all circumstances, simply better decision-making in more circumstances than a duller person. Some problems forms are inherently difficult and ambiguous. For example, it is easier to understand natural frequencies than percentages with decimal point. Apart from intelligence, social pressures and emotional attachments influence decisions.Modern IQ tests give one overall figure, and also figures for 3 to 4 component indices, usually verbal comprehension, perceptual organisation, working memory, plus processing speed. The single figure is usually the best predictor, but the others have their place in specific circumstances. The fact that one single number is the best predictor of human achievements is testimony to its power.40% is the heritability estimate for children, but it rises to 60% plus for adults. 70/30 is not a bad estimate for wealthy countries, 50/50 for very poor ones…. People from profoundly different cultures make the same sorts of errors on culture reduced tests, and the pattern suggests a largely universal problem-solving capacity. The predictive power of intelligence is similar in culturally different countries.
The point in bold is key. Out of all the factors that people think explain why certain people fail at life and others succeed, intelligence, even as imperfectly but reliably measured by one simple number, is the most important. The way science discovered this is also interesting: by controlling for intelligence in studies of other factors. Level of education, parental socio-economic status, reaction times, etc. turn out to be strongly correlated with, and very likely caused by, intelligence. On average, in the aggregate, the wealthier you are, the smarter you are, and wealthy parents pass those genes onto their children.
This is very different from what many people believe, or wish were true.