19th century Wilhelm Wundt, Gustav Fechner, and Francis Galton claim that individual differences in people’s cognitive abilities can be empirically measured.
1904 British psychologist Charles Spearman claims intelligence can be summed up in a single number.
1938 British psychologist L.L. Thurstone identifies seven independent factors that make up a person’s “primary abilities” or intelligence.
1969 Philip E. Vernon estimates that intelligence is 60 percent inborn.
1974 US psychologist Ellis Paul Torrance produces his own tests of creativity, which are most widely used today.
Although intelligence, ...