A reader asked which was the better test.  I once asked J. Philippe Rushton which IQ test he would put more trust in if they gave different results: The Raven or the Wechsler.

“They’re both excellent tests,” he gushed, but the problem with the Wechsler he felt, was that there’s a lot more room for scoring error because the examiner has to time you to the second on certain puzzles, and various verbal questions require subjective scoring, so in a case where the two tests disagreed, Rushton placed his vote with the Raven.

However the Wechsler is probably much more g loaded, and recent editions of the Wechsler include a Matrix reasoning subtest, so now the Raven has been reduced to just another Wechsler test.

The Wechsler probably also has more predictive validity, not just because it’s more g loaded but because it measures non-g abilities that are useful in life like verbal skill, spatial ability, processing speed, memory, and social understanding.

One of the great disappointments for psychometrics was discovering that the Raven was not the culture-fair test so many psychologists had hoped.  In fact it shows some of the largest Flynn effects ever recorded, though this doesn’t necessarily prove it’s the most culturally biased, as the Flynn effect has a biological component (nutrition increasing brain size which might in turn be increasing IQ) and the biggest Raven Flynn Effects were in countries like Holland, where people have been getting taller so rapidly that brain size is likely exploding.

Nonetheless IQ gains of 7 points per decade are unlikely to be entirely caused by exploding brain size so we’re forced to admit the Raven is sensitive to something changing in the culture, and thus is not culture fair.

People think culture bias means the Raven must be measuring some kind of knowledge or skill, but I suspect the culture bias is more subtle.  When Rushton administered the Raven to a bunch of gypsy adults they had shockingly low scores (only IQ 70 on average), far lower than the IQ 85 that had been reported for gypsy children.

My guess is dropping out of school made the gypsies intellectually lazy and so their Raven scores (though not real intelligence) declined rapidly with age, relative to the white reference group, most of whom stayed in school.

Because so many gypsies complained that the test was giving them a headache, it was clear their minds weren’t used to working hard intellectually.  For me the lesson was a true culture reduced test needs to be “fun” like some of the hard-core Performance subtests on the Wechsler, not hard work like the Raven.

The fact that some studies show IQ declining when kids go on summer vacation is more evidence for the intellectual lazy factor.

The other day I was at a bar when a woman confronted me. “You don’t remember me, do you.  Oh how could you, you were just a teenager, but you gave me a test!” she reminded me.

It took me a while but I remembered she was the delinquent older sister of a childhood friend who had had shocked her upper middle class family by running away from home to dabble in drugs and prostitution.  In high school, my friend and I would sneak downtown to stay at her apartment.

“I just wanted to give you a hug” she said sweetly, “because of you I ended up getting my college diploma!”

“What did I do?” I asked puzzled.

“You always used to give me those tests,” she explained, referring to some Raven items I would ask her to solve when I first learned about the test. “So when it came to taking the exam to get into college, I was totally prepared.” (Unlike our universities, Canadian colleges use entrance exams because many applicants are high school dropouts who lack basic skills)

Apparently I had cured her intellectual laziness.