Effectively, an IQ test is a battery of tests that seeks to define the boundary of various mental abilities. Each subsection of tests seeks to test one facet, but all subsets have a positive correlation to what researchers call g, which is general intelligence. This highlights several things:
- Since it's impossible to test for g directly, we can only glimpse at it via factor analysis.
- IQ score aren't an absolute, but are only relative to the rest of the population. An IQ score doesn't quantify anything.
- IQ scores are fairly stable in adult life.
- When it comes to IQ, you really find out that life isn't fair. People with higher IQ are healthier, have better jobs, make more money, are happier, and live longer.
- The Multiple Intelligences stuff has no empirical evidence to support it. And that doesn't bother Howard Gardner!
- IQ has a highly heritable component. In fact, the research studies in existence indicate that identical twins have IQs that converge over time, rather than diverging as you might expect!
- Different brains work differently, and what gives one person high IQ could be a completely different subset of abilities that work differently from another individual who has similarly high IQ. Men and women, for instance, demonstrate different brain areas that are correlated with high IQ, so a man and a woman with the same IQ score still could have brains that work differently.