But again... where is this coming from... data? Extrapolation?
The types have average Big 5 profiles calculated by people who had been first manually typed by the EI staff and then given a personality questionnaire
From there, we know how personality traits correlate with intelligence (they mostly don't very much, except for Openness/Intellect), and so all else being equal we can make a decent guess as to which way people of a type lean to, on average.
Plenty of concerns with IQ as a measure of cognitive ability. First - there's more than one IQ test out there. Second - the Binet-Simon test, arguably the first IQ test, was developed to identify students needing special education; 100+ years down the road, studies indicate that IQ scores strongly school positively correlate with SAT scores, yet there is not an overwhelming amount of study regarding g, the general intelligence that IQ is supposed to measure, and academic achievement or achievement in later life (furthermore - how to define/categorize achievement, exactly, when it looks different for different individuals) - which also leads into the question of whether higher internal intelligence necessarily correlates with better external outcomes (which also leads to the question of what "intelligence", exactly, entails). Third, the issue of IQ across cultures - different ethnic groups and/or cultures scoring differently - external validity issues, internal, or different groups having different average IQs? Last thing I will mention - though not the only other concern - "intelligences" that are not well accounted for by IQ, like musical ability, artistic ability, emotional and social intelligence... it's not that IQ is useless, it just may be mis-used and/or over-applied. IMO it should be treated like the imperfect tool it is, not like a concrete marker. It's more like taking the MBTI than measuring one's height - an indicator, rather than a strict measure.
The first concern is something scientists have pretty unsurprisingly thought about. It's technically possible that different intelligence tests wouldn't measure the same thing. To test that, you'd have to give the same set of people multiple different intelligence tests, calculate the g factors for each one and see if they are similar. This study has been done. The g factors correlated with each other at 0.98-1, if memory serves. They were the same thing.
Secondly, there
is a huge amount of research on
g/General Cognitive Ability. You just don't hear much about it, but it's been correlated to a huge number of things - school success, work, life outcomes like criminality, disease, likelihood of dying in a car accident. Scientists are exploring its relation to different personality traits at ever more granular level, the structure of intelligence differences between people has been proposed to not fit the common fluid-crystallized model (which is a decent model for how things happen inside a person, but the differences in ability between people seem to differ along the lines of verbal, perceptual/nonverbal and the ability to mentally rotate three-dimensional objects - this last one running contrary to the assumptions of the researchers who originally discovered the new VPR model), neuroimaging research is constantly being done to gain insight into the physical correlates and possible ultimate causes of intelligence (turns out the brains of more intelligent people use less energy rather than more, as the researchers initially assumed).
Higher intelligence absolutely correlates to better outcomes - more education, all else being equal, better health and longevity, less chance of dying in a car accident, less risk of criminality, incarceration, dropping out of school, long-term unemployment, women having illegitimate children, and the list goes on. Wikipedia lists general cognitive ability as predicting performance in "every kind of work studied to date".
As far as group differences go, they plainly exist, and IQ seems to be similarily predictive for eg. Black people living in Africa as it is for a pile of random ********. What the
causes of the observed score differences are is a massively gnarly topic that is hard to understand and where words have to be chosen carefully - not out of any sense of propriety, but simply for the sake of saying anything correct. To say the evidence is complicated is an understatement.
As far as musical ability and the like go, there are valued human abilities that are nevertheless not intelligence, per se. People like to call them that but it mostly muddies up language, while psychometrically what is and what is not intelligence is quite clear. As far as IQ being misused, yes, definitely. Over-applied is kind of a weird claim when the trait in question is related to damn near anything you can think of, even if it's not the sole or main player in many.
As far as the height comparison goes, it very much is like measuring your height - the ruler has to be a little more indirect is all.
