Hundreds of studies' conclusions on the benefits of intelligence all correlate with fluid intelligence, the ability to rapidly assimilate knowledge and use it to solve problems.

The claim is that the benefits of intelligence found across many ("hundreds of") studies all correlate with fluid intelligence, defined as the ability to rapidly take in and synthesize knowledge and use it to solve problems. True: the psychometric literature shows that the outcomes linked to intelligence in such studies are consistently associated with fluid intelligence (or g, which is closely related) and that the definition is standard. Mostly true: the literature mostly measures general intelligence (g) or IQ, which is strongly correlated with fluid intelligence, so the claim is substantially right but loose on the construct; or the definition is somewhat off. Mixed: many outcomes track crystallized as well as fluid abilities, so the claim captures only part of the picture. Mostly false: the studies mostly measure g, IQ or crystallized ability, and attributing their findings to fluid intelligence specifically overstates it, or "all" is clearly contradicted. False: the literature shows that the benefits of intelligence do not correlate with fluid intelligence.

Set before the research began.

1. E1 On the prediction of human intelligence from neuroimaging: A systematic review of methods and reporting bioRxiv (preprint, Vieira et al.) · 28 October 2021

   “We identified four constructs reported as outcomes. GF is an outcome in 20 (67%) studies, IQ in 6 (20%) studies, general intelligence, general cognitive ability or G appears in 4 (13%) studies and cognitive ability appears in 1 (3%) study.”

2. E2 The neuroscience of human intelligence differences - Nature Reviews Neuroscience Nature Reviews Neuroscience · 10 February 2010

   “Intelligence can be reliably measured, is stable in rank-order across the lifespan, and is predictive of many important life outcomes, including educational and occupational success, health and longevity.”

3. E3 Fluid ability, crystallized ability, and performance across multiple domains: a meta-analysis University of Iowa (Iowa Research Online, doctoral dissertation by Bennett Eugene Postlethwaite) · 2011

   “However, as hypothesized, crystallized ability measures were found to be superior predictors of academic performance compared to their fluid ability counterparts.”

4. E4 Knowledge Is Power for Medical Assistants: Crystallized and Fluid Intelligence As Predictors of Vocational Knowledge PubMed Central (peer-reviewed journal article) · 1 February 2018

   “Crystallized intelligence emerged as the strongest predictor of vocational knowledge at every stage of VET, while fluid intelligence only showed weak effects.”

E2, a review in Nature Reviews Neuroscience, links educational, occupational, health and longevity outcomes to intelligence in general, without specifying fluid intelligence. E3, a meta-analysis, found that crystallized ability predicted academic performance better than fluid ability. E4 found crystallized intelligence was the strongest predictor of vocational knowledge, with only weak effects from fluid intelligence. E1 shows that even neuroimaging studies of intelligence use a mix of constructs (fluid intelligence, IQ, g). So the outcomes track crystallized and general ability as well as fluid ability, and the claim captures only part of the picture.