"Psychologists began by asking which type of factor, hereditary or environmental, is responsible for individual differences in a given trait . . . a more fruitful approach is to be found in the question, 'How?' " --Anne Anastasi, Psychological Review, 1958
![](http://labs.la.utexas.edu/harden/files/2013/07/depts_psy_Harden-Paige_w200h300.jpg)