Academic journal article Mankind Quarterly

Does Your Family Make You Smarter? Nature, Nurture and Human Autonomy

Academic journal article Mankind Quarterly

Does Your Family Make You Smarter? Nature, Nurture and Human Autonomy

Article excerpt

Does Your Family Make You Smarter? Nature, Nurture and Human Autonomy James R. Flynn Cambridge: Cambridge University Press 2016, 258 pages

Jim Flynn's new book, Does Your Family Make You Smarter?, makes a single and very important contribution to the public understanding of intelligence by giving us a new way of evaluating the extent to which environment impacts IQ. For this reason alone, the book is certainly worth reading.

Flynn points out that studies of identical twins have previously shown that intelligence is roughly 0.8 heritable, meaning that 80% of the variance in how intelligent we are is a function of genes. However, intelligence only reaches this level of heritability among adult samples. It is much lower among child samples. Children are typically slightly more or less intelligent than their parents, though due to unlikely genetic combinations there can be very significant differences. When you are a child, your parents are controlling your environment, and it therefore reflects their innate intellectual capacity rather than yours. This can have the effect of either strongly boosting your intelligence (if your parents are much smarter than you) by pushing it to its phenotypic limit, or (if they are much less intelligent than you) retarding your intelligence by raising you in an intellectually un-stimulating environment which will push your IQ down to its phenotypic minimum.

Flynn shows - in an always lucid and enjoyable written style - that as we leave the environment of our parents, we start to create our own environment which reflects our own innate intelligence and it is at this point that the heritability of intelligence rises to 0.8. Less intelligent children raised in a highly stimulating environment, left to their own devices, will start to give up regular reading of books, the watching of documentaries and other such pursuits that their intelligent parents may have encouraged. Smarter people will start to meet more and more people like them and spend more and more time having intelligent conversations, rather than discussing football with their parents. And so their IQ - their intelligence compared to others of their age - will rise, while that of the less intelligent will start to fall. This is why, Flynn notes, a moderately bright child of very intelligent parents will show a great deal of promise, which will never be fulfilled.

To demonstrate the importance of your family environment in determining your adult intelligence, Flynn presents us with what he calls the 'Age-Table Method,' which is the book's main innovation. Until now, it has been argued that 'family effects' - the impact (positive or negative) of your family background on your IQ - wears off by about the age of 18, as this is when you are generally fairly autonomous. Flynn looks, on various IQ tests, at the correlation between IQ scores at different ages and shows that, in fact, the influence of your family is far more pervasive than previously thought. The new method allows him to persuasively argue that family effects last until about the age of 30. This makes intuitive, as well as now empirical, sense. …

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