One might believe, after studying the correlational studies of Bouchard et al (1990), that most of our behaviour is genetically determined. However, what is missing in this discussion, is the interaction between environment and genes – how some environments can interact positively with heritability to enhance the effect, and some can have a negative effect. To take an extreme example, if a baby is born having inherited, as many believe, 70% of her intelligence from her above-averagely intelligent parents, but then by some misfortune the family is forced to move to an area with very poor schools, and the child is bullied and unhappy and cannot reach her potential, then the chances are that she will score below average on standard IQ tests, and the heritability factor will be reduced. If, on the other hand, she has a lot of intellectual stimulation as a child, is very happy with school and her teachers, then her environment is acting with her inherited ability to enhance it.
This is an over-simplification, but can explain why siblings with similar IQs and similar behaviour traits often have very different lives. This March 2015 article explores this well. very useful for those of you studying HL Biology.
This post was inspired by Dr Laura Swash
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