Some
people are simply smarter than others, that
intelligence is a unitary trait, and that individual differences are accurately reflected in the intelligence quotient (IQ) obtained from an intelligence test. It''s possible to find those who argue against the existence of IQ, against the heritability of IQ, and, going a little further, against the value of quantitative
genetic analyses of how genetic variation contributes to human behaviour. Nevertheless, psychologists still work with intelligence tests, using separate measures of performance and verbal IQ, as well as the full-scale IQ score (the one that needs to be over 150 if you want to become a MENSA member), largely because there isn''t anything better.the well known bell shaped curve (with the majority of people
having a mid-range IQ and fewer numbers of people having very high or very low IQs) is interrupted at the lower end of the distribution by a small blip. Since each
child would be brought up in a
different environment, by a different mother, the genetic effect on IQ could be estimated by looking for correlations in the offsprings'' IQ.
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