What do IQ scores actually measure, and why do differences exist between groups?

IQ General
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What do IQ scores actually measure, and why do differences exist between groups?

I see this topic come up a lot but most discussions either go full dismissal or full determinism. Neither feels right to me. IQ tests have been around for over a century and the psychometric research behind them is actually pretty solid. They reliably predict academic performance, job outcomes, and other real world measures. But that doesnt mean the scores tell the whole story.

What gets me is the group difference debate. People either pretend the data doesnt exist or jump straight to genetic explanations without accounting for environment. Both moves seem intellectually dishonest. Socioeconomic conditions, access to quality schooling, nutrition, test familiarity, and chronic stress all affect cognitive performance in measurable ways. The science on this is not really controversial among researchers.

So what is the most accurate way to understand IQ scores and the differences we see across groups? Genuinely want to hear different perspectives on this.

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IQ tests measure specific cognitive skills like working memory, processing speed, and abstract reasoning. They dont capture everything about intelligence. Group differences in scores are real in the data but they reflect environmental factors like education quality, nutrition, and socioeconomic conditions just as much as anything else.

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Worth noting that differences within groups are way larger than differences between groups. The overlap between any two populations is huge, so a group mean tells you almost nothing about any individual. Research consistently points to early nutrition, schooling quality, and reduced poverty stress as the biggest drivers of cognitive performance.