Why we can’t replicate past psychological tests.
In the twentieth century, experimental psychological shifted from the study of the mentally ill to research on the cognitive and personality development of basically normal people. Soon there was a plethora of theoretical models on the formation of personality, with different ways of rating personality–too many. In 1961, Ernest Tupes and Raymond Christal sorted through the major theories to see what factors were used repeatedly and settle on five of these named surgency, agreeableness, dependability, emotional stability, and culture. 
This model has been tweaked frequently and the factors renamed; they are typically referred to as Extroversion, Agreeableness, Conscientiousness, Neuroticism and Openness to Experience.  But the theoretical model was only the beginning. Other psychologists developed questionnaires to test for these factors, and performed research to determine the norms , where the average for a population lies. Then, they started performing experiments based on the factors. More than half a…
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