THE ROUGH GUIDE TO PSYCHOLOGYwhite people (little wonder, given that black people were generally less
educated and poorer). When these results were combined with a highly
dubious 1912 analysis by Goddard entitled “The Kallikak Family: A Study
in the Heredity of Feeble-Mindedness”, the eugenics movement had all
the ammunition it needed. By 1932, twenty-seven states in America had
passed laws permitting the sterilization of people regarded as feeble-
minded. Stephen Murdoch, the author of IQ: How Psychology Hijacked
Intelligence (2009), estimates that over sixty thousand people in America
were sterilized in the twentieth century – the specious aim being to stop
the spread of unintelligent genes. In Nazi Germany, the figure reached
over four hundred thousand.
Claims and counter-claims about racial differences in intelligence
continued to be bandied around for most of the twentieth century,
culminating most famously in The Bell Curve, a controversial 1994 best-
seller by the late Richard Herrnstein and Charles Murray. In a recent
review of the field, the psychologists Stephen Ceci and Wendy Williams
at Cornell University defended the continued study of race differences in
IQ, arguing that unsavoury claims are best countered through empirical
research. They say their own findings suggest racial differences in IQ are
due to environmental, not genetic, factors.
Another highly sensitive social issue thrown up by intelligence testing
concerns death sentencing in US courts. Following the case of Atkins vs.
Virginia, in 2002 the US Supreme Court ruled that a criminal deemed to
be mentally retarded cannot be sentenced to death. This has led to trials
in which expert witnesses (usually psychologists) for both the defence
and prosecution clash over how highly a defendant has scored on intel-
ligence tests.
Are we getting cleverer?
When the test scores of today are compared with those in previous
decades, going back to around 1900, a consistent pattern emerges –
scores seem to be progressively higher. In statistical terms, the size of this
increase is one standard deviation or 15 IQ points in the last fifty years
(in Britain this would mean that, measured against today’s standards,
seventy percent of Victorians would have an IQ of less than 75 – close to
official “mental retardation” levels). This phenomenon has come to be
known as the Flynn effect, after the New Zealand political scientist James
Flynn who first documented it. By his account, the trend has been found
in every country for which we have the necessary data, which in 2007