Differential Psychology

Differential psychology studies the ways in which individuals differ in their behavior and the processes that underlie those differences, developing taxonomies of psychological individual difference. It is distinguished from the mainstream of psychology, which more often studies groups or general processes, and the field was first named by William Stern in his 1900 book Uber Psychologie der individuellen Differenzen, On the Psychology of Individual Differences, a name Stern himself retained. Charles Darwin's 1859 work first spurred scientific interest in individual differences, a line of inquiry his half-cousin Francis Galton pursued further by attempting to quantify individual difference directly; much later psychological research, by contrast, has tended to treat differences between individuals as statistical error to be controlled for, comparing the mean performance of treatment and control groups rather than treating those individual differences themselves as the phenomenon of interest, which is the gap differential psychology exists to fill.