Final answer:
The third scale of the Minnesota Multiphasic Personality Inventory (MMPI) is the validity scales. These scales assess the truthfulness of the responses and help in detecting possible attempts of 'faking good' by the respondent.
Step-by-step explanation:
The Minnesota Multiphasic Personality Inventory, commonly known as the MMPI, is a comprehensive personality test designed to assess various aspects of a person's personality and psychological stability. This inventory consists of a series of true/false questions and is intended to create a clinical profile of the individual. The MMPI includes three main types of scales: clinical scales, content scales, and validity scales. The validity scales are designed to help determine the veracity of the responses, check for response consistency, and identify individuals who may be trying to present themselves in an overly favorable light, a concept known as 'faking good'.
One well-known validity scale within the MMPI is the 'Lie Scale' or 'L' Scale, which includes items to ascertain if the respondent is potentially underreporting psychological problems. Therefore, the correct answer to the question regarding the third scale in the MMPI apart from the clinical and content scales is (c) validity scales.
The third scale of the Minnesota Multiphasic Personality Inventory, alongside clinical and content scales, is the validity scales. These scales are crucial for ensuring the accuracy and honesty of the responses provided in the inventory.