aUniversity of Ulster, Coleraine, Northern Ireland, BT52 1SA, UK
Received 23 March 2008; revised 17 July 2008; accepted 17 July 2008. Available online 21 September 2008.
Results of five studies show that during the second half of the twentieth century there were increases in the Development Quotients (DQs) of infants in the first two years of life. These gains were obtained for the Bayley Scales in the United States and Australia, and for the Griffiths Test in Britain. The average of 19 data points is a DQ gain of approximately 3.7 DQ points per decade. Similar gains of approximately 3.9 IQ points per decade have been present among pre-school children aged 4–6 years. These gains are about the same as the IQ gains of school age students and adults on the Wechsler and Binet tests. This suggests that the same factor has been responsible for all these secular gains. This rules out improvements in education, greater test sophistication, etc. and most of the other factors that have been proposed to explain the Flynn effect. It is proposed that the most probable factor has been improvements in pre-natal and early post-natal nutrition
More from professor Lynn; a bit of an ass at times, but not stupid. This suggests that most of the IQ gains made through the 20th century a mainly attributable to better nutrition (we are about 30 points smarter than we used to be in the Victorian era).
This would also be another kick in the teeth for the ‘environment only’ supporters who believe we are all born the same, but our IQ’s vary solely from environmental factors. Generally malnutrition isn’t common even among the poorest groups in the West, so this makes most IQ differences you see between individuals due to genetics. The current estimate of heritability is 70% ish, with most of the 30% being nutrition and infantile stimulation. I’d like to see a study of vegetarian/vegan children to see if they compare well to omnivores.