I have written quite a few postings on the genetic transmission of IQ, often referred to the heritability of IQ. A number of recent studies have confirm the point that variances in IQ can be explained by genetic factors (to the tune of about 60%), while environmental factors account for up to 40% of variability in IQ. This would suggest that IQ is genetic. These finding represented a departure from the earlier studies which had suggested that 50% of IQ was heritable. The literature is increasingly clear that nature trumps nurture and that the genetic transmission of IQ is real.
A new series of studies have weighed in on the debate, and findings have only strengthened the camp of IQ being genetic. Florida State University recently published a study which employed the well regarded database called the National Longitudinal Study of Adolescent Health. The study looked at the IQs of adopted children and their adoptive parents. The study concludes that there was little evidence to suggest that environmental factors and parenting had any level of impact on the IQs of the adoptive children. To make matters worse, it even went on to conclude that “maternal attachment” was negatively correlated to the IQs of the adoptive children. From this piece of research, it is clear that IQ is genetic.
Another important study was from Kings College London, which is at the forefront of the analysis of the human genome. KCL researchers employed “Genome Wide Complex Trait Analysis”. The researchers found that 94% of the relationship between socioeconomic status (SES) and IQ was mediated by genetic transmission by the age of 7, and 56% by the age of 12. Again, the overall conclusion is that IQ is genetic and that SES is also largely rooted in genes.
So IQ is genetic, are parents wasting their time?
The proportion of IQ which is said to be attributable to ‘environmental’ factors may be up to 40%, although recent studies clearly point towards the increasing strength of the genetic explanatory factor. So what is going on? Well, the term ‘environmental’ factors is in fact misleading. That is, the body of literature calls these ‘non shared’ environmental factors. In other words, these are environmental factors that go beyond household level of quality of life. These non-shared environmental factors may be the result of an accident, illness, or specific life events that may not even be share by siblings and even identical twins.
The conclusions of this research also points to the fact that parents need to relax a little. Pushing children for greater academic achievement may to some extent be futile. Good, rather than great home and learning environments should be sufficient for the children to achieve their full potential. This also suggests throwing money at the problem is unlikely to help. The extra cash is probably best saved and spent on a trip to Disney Land and going on family holidays and having a good time.
That said, I continue to believe that favorable home and learning environments may create short term boosts in academic achievement, which in turn helps children get through their schooling with greater relative ease. And each additional year of schooling is correlated with higher crystallized intelligence which is one important component of overall intelligence.
Yes IQ is genetic, so parents should give themselves a break and focus on their own / and their children’s happiness.
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