February 09, 2009

According to Flynn, nutrition not behind "Flynn effect"

See a recent paper by Lynn where the importance of nutrition for the Flynn effect (secular increase in IQ) was argued. Another paper on Denmark (and another) which also sees a recent decline in IQ scores, a reversal of the Flynn effect.

From this paper's conclusions:
The totality of the evidence supports a summary conclusion. Enhanced
nutrition has made us taller people and poor nutrition has made us more obese. But
our diet today probably does not make us very different people from our grandparents as far as cognitive competence is concerned. Our brains have altered since 1900, and they are better brains for solving the problems of our time. But they have altered rather like a muscle, that is, they have altered because we use them differently than our parents and grandparents did. The causes of this are many and the effects of nutrition, at least since privation has been banished, are too weak to stand out from the crowd.

Economics & Human Biology doi:http://dx.doi.org/10.1016/j.ehb.2009.01.009

Requiem for nutrition as the cause of IQ gains Raven's gains in Britain 1938 to 2008

James R. Flynn


The hypothesis that enhanced nutrition is mainly responsible for massive IQ gains over time borrows plausibility from the height gains of the 20th century However, evidence shows that the two trends are largely independent. A detailed analysis of IQ trends on the Raven's Progressive Matrices tests in Britain dramatizes the poverty of the nutrition hypothesis. A multiple factor hypothesis that operates on three levels is offered as an alternative instrument of causal explanation.

The Raven's data show that over the 65 years from circa 1942 to the present, taking ages 5 to 15 together, British school children have gained 14 IQ points for a rate of 0.216 points per year. However, since 1979, gains have declined with age and between the ages of 12 to 13 and 14 to 15, small gains turn into small losses. This is confirmed by Piagetian data and poses the possibility that the cognitive demands of teenage subculture have been stagnant over perhaps the last 30 years.



Maju said...

One thing does not need to exclude the other: malnutrition is still a major problem in large areas of this planet, maybe affecting a majority of children or at least a very large minority, and can well be behind reduced IQ (alleged) in many areas of the world.

But I do feel that Flynn has a good point in comparing the brain with a muscle: an organ that adapts to the demands of real life. In fact the differences in intellectual achievements in humans are surely much bigger than those in physical achievements, so the dynamic adaptation may be even much larger than that of our brawn, given the necessary intellectual pressure (school, media, work, internet... society in general) - or the lack of it.

mathilda said...

Junk food is to blame. We may be eating as much (if not more) but the quality of the food in terrible - not a fresh vegetable or omega three oil in sight.

Juvenille scores are meaningless anyway. Why anyone tests sub adults and attaches any significance to the results I'll never know. Kids IQ scores are pretty malleable, easily temporarily forced up a notch or kept back by poor circumstances. Test them at 21, then it'll mean something.

Jack said...

How about considering the change in the "ethnic" composition of the "British" populaion over the past three decades.

BlaiseVillaume said...

Between the influx of foreigners with significantly lower IQ's, an education system that run at the level of the lowest common denominator, and a cultural shift in how education is perceived, and as Mathilda mentioned, the elasticity of children IQ's, how can anyone try to make a conclusion without accounting for these variables?