In summary, cognitive ability testing by itself has been shown to have high levels of validity, but comes with issues relating to adverse impact. Personality tests, on the other hand, have historically been proven to have low validity due to the lack of a common understanding on what constitutes personality, and the non-standardized measures available. But a growing number of research studies show that the best way for organizations to achieve close to optimal validity and job performance prediction, is to create a predictor composite that includes a measure of cognitive ability and an additional measure such as a personality test.