April 27, 2006

Strange new IQ study and the effect of age

We read:

"Girls have big advantage over boys on timed tests

"Vanderbilt University researchers Stephen Camarata and Richard Woodcock discovered that females have a significant advantage over males on timed tests and tasks. Camarata and Woodcock found the differences were particularly significant among pre-teens and teens....

Though males and females showed similar processing speed in kindergarten and pre-school, females became much more efficient than males in elementary, middle and high school." The researchers found that males scored lower than females in all age groups in tests measuring processing speed, with the greatest discrepancy found among adolescents. However, the study also found that males consistently outperformed females in some verbal abilities, such as identifying objects, knowing antonyms and synonyms and completing verbal analogies...

The researchers found no significant overall intelligence differences between males and females in any age groups. The research will be published in the May-June 2006 issue of the journal Intelligence. Camarata and Woodcock compiled their results through an evaluation of three sets of data collected from 1977 to 2001 as part of the Woodcock-Johnson Series of Cognitive and Achievement Tests."

Source

That is a really strange set of findings. Higher mental speed on a whole range of indices is normally associated with higher IQ so girls should have shown up as more intelligent but they did not. Among adults, males show up as having slightly higher IQ scores than females but not in this study. And strangest of all is that males outperformed females on verbal abilities. Probably the least disputed finding in the whole of IQ research is that FEMALES score highest on verbal abilities, with males doing best on visuospatial abilities.

So what the heck is going on here? It would be easy to dismiss the study as too much of an outlier to be anything but a product of poor methodology but I believe that the results are not as mysterious if we are aware of Lynn's huge summary of all the past research on these questions.

What Lynn showed was that results obtained with schoolchildren are not the same as the results obtained with adults. And I am now going to say why. And I am going to say why in a way that will offend a lot of people. But I am going to say it that way because it is true and the truth concerned helps us to see a particular finding in a way that all scientists seek -- as being part of a larger pattern. And that fact is that maturation speed is inversely correlated with final level obtained. Since that is a hopelessly academic way of saying anything, however, I will now say it in another brutally frank way: Chimpanzees, blacks and women grow up faster than white males and the faster they mature, the lower is the intelligence level that they finally reach on average.

Yes. I know that most people will accuse me of being worse than Hitler for saying that but, as the old Scottish saying has it: "Facts are chiels that winna ding" (Roughly translated: "Facts are guys that cannot be defeated"). I am sorry to be the messenger of a deeply unpalatable truth but somebody somewhere some day has to tell it to the general public.

And the authors of the study above do note that their results vary with age so that is clearly the decisive factor. In other words, if the study had been repeated with adults, the results would have been different. Females scored equally with males on average simply because males had not reached their peak at the ages studied.

There are still some puzzling parts of the study, though. Although the slower maturation of males explains the male/female parity in average IQ at the ages studied and perhaps explains the higher female processing speed observed, the unprecedented findings with verbal abilities remain to be explained. My best guess is that the tasks used to assess verbal abilities were atypical -- though it does not sound as if they were. Maybe Richard Lynn or J.P. Rushton may be able to shed some light on it in due course.



Journal abstract:

Sex differences in processing speed: Developmental effects in males and females

Stephen Camarata & Richard Woodcock

Abstract

The purpose of this study was to compare the cognitive abilities and selected achievement performance of females and males across the lifespan on standardization samples of broad cognitive abilities in 1987 participants (1102 females, 885 males) from the WJ III, 4253 participants (2014 males, 2239 females) from the WJ-R, and 4225 participants (1964 males and 2261 females) from the WJ-77. Preschool through adult cohorts were included in the analyses. The results indicated that males scored significantly lower on estimates of Gs (processing speed) in all three normative samples, with the largest difference evident in adolescent subgroups. A secondary finding was significantly higher scores for males on estimates of comprehension knowledge (Gc) in all three samples. Follow-up analyses of the achievement tests also indicated lower performance for males on speeded tests such as reading fluency and writing fluency. There was a high degree of concordance across tests and no sex difference was observed in overall estimates of general intellectual ability (GIA) on the WJ III. The educational implications of these findings are discussed with an emphasis on the adolescent (high school) cohort.

Intelligence, Volume 34, Issue 3, May–June 2006, Pages 231-252




Go to John Ray's Main academic menu
Go to Menu of longer writings
Go to John Ray's basic home page
Go to John Ray's pictorial Home Page
Go to Selected pictures from John Ray's blogs