Psychology, “the scientific study of behaviour and mental processes”, is in serious trouble. Five years ago Professor Brian Nosek at the University of Virginia sought to counter criticisms of the intellectual rigour of his discipline through the gold standard of scientific certainty – replicability.
He selected 100 papers with “positive” (ie statistically significant) results selected from three prestigious psychology journals investigating a range of topics (the most effective way to teach arithmetic, differences in how adults and children respond to fear, etc) and with the assistance of an international group of almost 300 colleagues set to work.
The verdict published last year in the journal Science was much worse than expected with a replication failure rate of 60 per cent – and even then the size of the effect in the 39 confirmed studies was half as big as first time round.This is almost certainly a considerable underestimate were the same litmus test of replicability applied to the thousands of studies published every year in the many less prestigious psychology journals.
This is no trivial matter. Indeed, this non-replicability probably matters more than for any of the other social sciences as the evidence from psychological studies is so influential in the public sphere of education and the criminal justice system. The demonstration of their unreliability has prompted much soul searching. “Scepticism is a core part of science and we need to embrace it,” Professor Nosek told The Guardian. “We should be our own worst critics.”
Fair enough, but I suspect that psychology’s current discontents are probably not resoluble by better methodology. The phenomenon of human individuality poses the greatest conundrum of our existence: how the same three pounds of protoplasmic stuff within our skulls should give rise to the distinctive personality of each one of us, both the billions with whom we share the planet and all who have gone before. The current consensus would attribute a causative role to the interplay of genes and environment but, if paradoxically, the evidence for each separately and on its own account is overwhelming and mutually exclusive. And that is deeply puzzling.
“The phrase ‘nature and nurture’ is a convenient jingle of words,” observed the Victoria polymath Francis Galton, “for it separates out under two distinct headings the innumerable elements of which each personality is composed”. His ingenious method for teasing out the distinction by comparing the character traits of identical and non-identical twins proved so definitive as to be almost embarrassing. “There is no escaping that nature prevails enormously over nurture … my fear is that my evidence may prove too much and be discredited on that account.”
A century later American psychologist Thomas Bouchard refined Galton’s techniques, studying 39 sets of identical twins separated at birth and brought up in very different circumstances. They included Barbara, the adopted daughter of a gardener, and Daphne, whose adopted father was a metallurgist. When they finally met at King’s Cross station, having been separated with no contact for nearly four decades, they discovered they were both frugal, liked the same books, had been Girl Guides and chose blue as their favourite colour. Both had the eccentric habit of pushing up their noses which they called “squidging”. They liked their coffee black and cold. They were both 16 when they met the men they were going to marry and both “laughed more than anyone else they knew”.
Bouchard had anticipated some character traits would prove more heritable than others but as the astonishing similarity of Barbara and Daphne suggests, his findings were almost boringly predictable in demonstrating the dominant role of heritability.
But turning to the second element of Galton’s “convenient jingle”, the formative influence of nurture, the evidence is just as overwhelming, illustrated most vividly in the way that children born into one society but brought up in another acquire its language, habits and values irrespective of their genetic inheritance.
The American anthropologist Ashley Montagu describes how the children of early settler communities in the United States kidnapped by the indigenous population “became so completely Indianised it was only by being informed of their origins from others that they learnt of their real extraction”.
Similarly, when 100,000 Korean children were adopted by families in the United States in the largest ever trans-cultural adoption programme they became completely Americanised within a single generation. This phenomenal plasticity where the young mind voraciously and remorselessly integrates all that it encounters would seem to trump genetic determinism.
This immensely persuasive evidence favouring the formative evidence of both nature and nurture implies this is a true dichotomy – like substance and form, mind and matter, electrons being both particles and wave, chance and necessity, being and becoming, each the irreducible antithesis of the other but also absolutely complementary. When grappling with the conundrum of human individuality metaphysics, not psychology, rules.
James Le Fanu is a doctor, medical columnist and science historian
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