Intelligence - Job

John E. Hunter attempt to estimate the relative contributions of general intelligence and context-specific knowledge in a very practical context: job performance in a range of jobs including manual jobs.

He found that IQ indeed correlated with job performance, but with knowledge as a mediating variable. This means that the best direct predictor of job performance was knowledge about the job, not IQ. IQ did relate to job performance, but not as directly as knowledge. Higher-IQ workers learn somewhat faster and therefore become more knowledgeable in their job sooner. But it's the knowledge that most directly accounts for the performance, however long a worker needed to accumulate it.

Intelligence - Horse racing prediction

Another research on people who claimed to be expert at predicting which horse would finish in what position. The investigators sat with the participants to see how they reasoned about the horses: the kind of knowledge they used, how thoroughtly they surveyed and balanced the evidence, and so on.

One finding was that some of the handicappers proved much better at the enterprise tha others, even though all had had some 16 years of experience. Second, the handicappers' success was not predicted by IQ. Third, success did relate to the cocmplexity of the handicappers' cognition in the context of handicapping. The better handicappers composed judgements that explicity took into account more interaccting factors than did the less successful handicappers.

Intelligence - Chess

To win a chess, the master player thinks further ahead. The master has a powerful mind that can keep track of many possibilities. In addition, the chess master is able to memorize the layout of pieces on a chess board at a glance, but amateurs could only reconstruct the position of seven or eight pieces.

However, another surprise finding is: when the arrangements of pieces at random on the chess boards, the master became like amateurs, only placing some seven or eight pieces correctly. Apparently, through years of experiencce, master players learn to see in a quick and intuitive way typical arrangements of pieces. This phenomenon is called chunking. With experience in a domain, people learn to enode the world in larger chunks that hang together. That is, the master player can take in an entire board in the form of a few chunks... providing the arrangement is natural to chess.

The master chess intelligence depended in good part on quick perceptual insight developed through years of play. Chess masters were not just smart in general; they knew a lot about chess specifically.

In principle, one might expect a person with high intelligence to deduce the rest - good positions, good attacks, good sacrificecs. In practice, people with high IQs are at the mercy of an experienced player of more modest IQ. Nothing count like a rich fund of experience.