Besides clinical scales, MMPI-2 also includes several validity or control scales. These were designed to assess test taking attitudes and response biases that might distort the picture presented by the clinical scale score alone. High scores of these scales may indicate invalid clinical scale profiles. The validity scales consider the tendency of people to create a favorable impression, and consist of items dealing with minor flaws & weaknesses to which most people are willing to admit.
People with high L (lie) scores appear impossibly good & virtuous. The F scale (validity score) was designed to detect deviant or atypical ways of responding to test items. High scores on this scale indicate those people who describe themselves as having a number of rare & importable characteristics. While the F scale was included to reflect people's carelessness & confusion in taking the MMPI, it has also come to be seen as a good indicator of psychopathology.
The K scale (defensiveness score) is more subtle than the L & F scale and covers several different content areas in which a person can deny problems (worry or suspiciousness). Its construction was based on the observation that some open & frank people may obtain high scores on the clinical scales, while others who are very defensive may obtain low scores. The K scale was devised to reduce these biasing factors. People who get high K scores are defensive, they tend to answer 'false' to items like 'I feel bad when others criticize me'. K corrections are made on a number of clinical scales in order to compare the scores of people who differ in these tendencies.
In addition to L, F, & K scales that were part of original MMPI, MMPI-2 has 3 additional validity scales. The Fb scale is intended to reflect a subject's tendency to answer later items in the text booklet differently than those that occur earlier. The VRIN scale indicates a subject's tendencies to respond inconsistently to MMPI-2 items. Inconsistencies result when subjects don't read content & respond in a random or near - random way. TRIN scale was developed to identify subjects who respond indiscriminately by giving either mainly true responses or mainly false responses without taking into account the meaning of the item statement.