help desk - statistics

I desperately need a course in statistics.

My question concerns this passage from a terrific article: The structure of human intelligence: It is verbal perceptual and image rotation (VPR), not fluid and crystallized by Wendy Johnson & Thomas J. Bouchard Jr.^* (pdf file)

Interestingly, though the correlations between the verbal and perceptual and perceptual and image rotation factors were high (0.80 and 0.85), the correlation between the verbal and image rotation factors was much lower, 0.41.

This study sets out to determine the "relative statistical performance of three major psychoetric models of huam intelligence," those being:

• Cattell-Horn fluid-crystallized model
• Vernon's verbal-perceptual model
• Carroll's three-strata model

The fluid-crystallized model, which has been dominant for some time now, didn't work.

Good.

I'm glad.

I'm glad because according to the fluid-crystallized model people get dumber as they age and their "fluid" intelligence gets less fluid. Or something.

This is why we're always hearing that for us old folk "experience and wisdom" have to make up for "ability to solve novel problems" or what-have-you.

Turns out that "experience and wisdom" and the "ability to solve novel problems" are the same thing.

Or so I gather. (If anyone who actually researches intelligence stumbles across this entry, I yearn to be fact-checked on this. Please. Chime in.)

At any rate: Bouchard's new study is good news for geezers because the fluid-crystallized model did not work out.

Nor did the "three-strata model." (Don't know what the three-strata model is; not going to find out any time soon.)

What did work is the verbal-perceptual model, which is pretty much the common-sense understanding of human intelligence most of us non-experts have always believed in.

I still don't really understand the distinction between verbal intelligence and perceptual intelligence. Generally speaking, however, it breaks down this way:

• "verbal: verbal fluency and divergent thinking [ed.: what is divergent thinking?] as well as verbal scholastic knowledge and numerical abilities"
  

• "perceptual speed, and psychomotor and physical abilities such as proprioception in addition to spatial and mechanical abilities"
  

Clear as mud!

What's interesting about Johnson's and Bouchard's study is that they discovered that one needs to add a third category, which is the ability to mentally rotate, manipulate, and twist two-and three-dimensional objects.

As we all know, this is a guy thing:

Interestingly, it is the image rotation abilities that have repeatedly shown the most robust sex differences among cognitive abilities (favoring males, Voyer, Voyer, & Bryden, 1995).

I'll get back to that.

In another post.

Here's my question.

I'm not understanding how verbal intelligence can correlate highly with perceptual intelligence, and perceptual intelligence can correlate highly with image rotation intelligence, but image rotation intelligence does not correlate highly with verbal intelligence.

How does that work?

Am I reading the passage incorrectly?

Is this an expression of a sex difference?

Or what?

Thanks in advance!



^* Bouchard directs the Minnesota Twin Study.

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