Nature-nurture debate


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The nature-nurture debate (1955 – present day). Between the mid 1950s and the early 1980s one of the main debates that dominated psychology was nature-nurture. The crux of the nature-nurture debate was the degree to which human attributes, particularly intelligence and personality, were determined by either genetic factors (nature) or environmental factors (nurture). This nature-nurture debate was particularly fierce in the area of intelligence, following the publication, and subsequent criticism, of Sir Cyril Burt's results from his study of the intelligence quotients (IQ) of separated twins. Over many years Burt claimed to have studied 58 pairs of monozygotic (MZ – from the same ovum) twins (popularly referred to as 'identical'). This was a larger number than any other researcher had been able to obtain. For that reason, Burt's claims that the IQs of separated MZ twins were more alike than those of dizygotic (DZ – 'non-identical') twins reared together was very influential in supporting claims that intelligence is largely inherited. However, it was later alleged that Burt at worst fabricated his results, and at best behaved in a 'dishonest manner' because he did not find as many separated twins as he had claimed.

The debunking of Burt's results even became the leading article on the front cover of an issue of the Sunday Times in 1976 and Burt was posthumously discredited by the British Psychological Society (BPS). The nature-nurture debate over intelligence generated a public debate between a leading hereditarian (someone who believes that intelligence is largely inherited) – Hans Eysenck – and the environmentalist who had first uncovered problems in Burt's reported statistics (Leon Kamin). This was published in 1981 in a book titled Intelligence: the battle for the mind. The debate has rumbled on since with publications such as The Bell Curve by Herrnstein and Murray (1994) and with various defences of Burt's conclusions and data. Few psychologists now argue for only one side of the nature-nurture debate. This is partly because most now accept that both genetic inheritance and environment play some part in all human psychological processes. The successful mapping of human genes in the Human Genome project has contributed new evidence to discussions of the heritability of psychological characteristics. However, the debate in psychology is now more one of the relative contributions of nature and nurture, and the specific mechanisms of interaction, than one of absolute dichotomies.