•A group of scientists discovered a gene that may be linked to intelligence
• The gene is located on chromosome 6
• The discovery has been met with skepticism by many
• To be able to measure such a slippery thing (like intelligence) in half an hour (IQ test) seems absurd.
• Indeed, the early measurement of intelligence was crudely prejudiced in motivation. Francis Galton, who pioneered the study of twins to tease apart innate and acquired talents, made no bones about why he did so:2 My general object has been to take note of the varied hereditary faculties of different men, and of the great differences in different families and races
• H. H. Goddard took an intelligence test invented by Alfred Binet and applied it to Americans and would-be Americans, concluding with absurd ease that not only were many immigrants to America ‘morons’, but that they could be identified as such at a glance by trained observers
•The history of intelligence testing has left most academics with a profound distrust of anything to do with IQ tests.
• When the pendulum swung away from racism and eugenics just before the Second World War, the very notion of hereditarian intelligence became almost a taboo.
• Human beings are capable of learning, after all. Their IQ can be influenced by their education so perhaps psychology should start from the assumption that there was no hereditary element at all in intelligence: it is all a matter of training.
• Just as the genetic determinists of the 1920s looked always for confirmation of their ideas and never for falsification, so the environmental determinists of the 1960s looked always for supporting evidence and averted their eyes from contrary evidence, when they should have been actively seeking it.
• Ordinary people have always known that education matters, but equally they have always believed in some innate ability. It is the experts who have taken extreme and absurd positions at either end
•IQ tests are biased, but they measure something.
• Different intelligences tend to be correlated. This was first noticed by Charles Spearman in 1904.
• Some statisticians argue that ‘g’ (general intelligence) is just a statistical quirk, while others think it’s a direct measurement of something real.
• ‘g’ works as a predictor of later performance in school better than almost any other measure. There is objective evidence for ‘g’.
• IQ scores correlate strongly with school test results and with the speed at which people perform certain tasks involving information retrieval.
• The heritability of IQ has been tested on twins and adoptees, and the results are startling: there is a substantial heritability to intelligence (whatever IQ is).
•In the 1960s, it was fashionable to separate twins at birth, especially when putting them up for adoption.
• Many times this was done with no particular thought, but in others it was deliberately done with concealed scientific motives.
• The most famous case is that of two New York girls named Beth and Amy, separated at birth by an inquisitive Freudian psychologist.
• The study proved the very opposite: the power of instinct.
•Studies show that intelligence is largely influenced by genes, rather than the environment found in one’s childhood home.
• However, this does not mean that the environment has no impact – it was found to account for a small percentage of IQ.
• The heritability of IQ increases as one gets older and accumulates more experiences.
•Studies that mildly exaggerate heritability because they are of families from a single social class show that heritability will be greater in an egalitarian society than an unequal one.
• The definition of the perfect meritocracy is a society in which people’s achievements depend on their genes because their environments are equal.
• With generally better childhood nutrition, more of the differences in height between individuals are due to genes: the heritability of height is, therefore, I suspect, rising.
• The same cannot yet be said of intelligence with certainty, because environmental variables – such as school quality, family habits, or wealth — may be growing more unequal in some societies.
• But it is logically false to conclude that because the difference between the IQs of one person and another is approximately fifty per cent heritable…that difference between average IQ scores of blacks and whites…is due to genes.
•Robert Plomin’s first gene discovery, the IGF2R gene, has been linked with intelligence.
• The function of the protein it encodes is ‘the intracellular trafficking of phosphorylated lysosomal enzymes from the Golgi complex and the cell surface to the lysosomes’.
• Plomin’s gene discovery has shown that there are other genes (besides IQ) that can influence intelligence.
•In the early 1990s, there was a revived interest in bodily symmetry because of what it can reveal about the body’s development during early life.
• Some asymmetries in the body are consistent (e.g. the heart is on the left side of chest in most people), but other, smaller asymmetries can go randomly in either direction.
• The magnitude of fluctuating asymmetry is a sensitive measure of how much stress the body was under when developing (stress from infections, toxins or poor nutrition).
• The fact that people with high IQs have more symmetrical bodies suggests that they were subject to fewer developmental stresses or more resistant to such stresses (which may be heritable).
• Support for this idea comes from Flynn effect: IQ scores are increasing all over world at an average rate if 3 points per decade; cause is unknown but might be due to improved childhood nutrition or exposure to visual images/puzzles.
•The high heritability of IQ suggested by twin studies is hard to square with the idea that IQ measures nothing innate, according to Flynn.
• Neisser suggests that the modern world is an environment that encourages the development of one form of intelligence – facility with visual symbols.
• If Neisser is right, this would be a blow to ‘g’, but it does not negate the idea that these different kinds of intelligence are at least partly heritable.
• after two million years of culture, human brains may have acquired (through natural selection) the ability to find and specialise in those particular skills
that the local culture teaches, and that the individual excels in.