第11章パーソナリティ

Roberto, Mikhail, and Nat are college friends and all want to be police officers. Roberto is quiet and shy, lacks self-confidence, and usually follows others. He is a kind person, but lacks motivation. Mikhail is loud and boisterous, a leader. He works hard, but is impulsive and drinks too much on the weekends. Nat is thoughtful and well liked. They are trustworthy, but very methodical and therefore have difficulty making quick decisions. Of these three, who would make the best police officer? What qualities and personality factors make someone a good police officer? What makes someone a bad or dangerous police officer?

A police officer’s job is very high in stress, and law enforcement agencies want to make sure they hire the right people. Personality testing is often used for this purpose—to screen applicants for employment and job training. Personality tests are also used in criminal cases and custody battles, and to assess psychological disorders. This section explores the best known among the many different types of personality tests.

Self-report inventories are a kind of objective test used to assess personality. They typically use multiple-choice items or numbered scales, which represent a range from 1 (strongly disagree) to 5 (strongly agree). They are often called Likert scales after their developer, Rensis Likert (1932) (Figure 11.16). Self-report inventories are generally easy to administer and cost effective. There is also an increased likelihood of test takers being inclined to answer in ways that are intentionally or unintentionally more socially desirable, exaggerated, biased, or misleading. For example, someone applying for a job will likely try to present themselves in a positive light, perhaps as an even better candidate than they actually are.

One of the most widely used personality inventories is the Minnesota Multiphasic Personality Inventory (MMPI), first published in 1943, with 504 true/false questions, and updated to the MMPI-2 in 1989, with 567 questions. The original MMPI was based on a small, limited sample, composed mostly of Minnesota farmers and psychiatric patients; the revised inventory was based on a more representative, national sample to allow for better standardization. The MMPI-2 takes 1–2 hours to complete. Responses are scored to produce a clinical profile composed of 10 scales: hypochondriasis, depression, hysteria, psychopathic deviance (social deviance), masculinity versus femininity, paranoia, psychasthenia (obsessive/compulsive qualities), schizophrenia, hypomania, and social introversion. There is also a scale to ascertain risk factors for alcohol abuse. In 2008, the test was again revised, using more advanced methods, to the MMPI-2-RF. This version takes about one-half the time to complete and has only 338 questions (Figure 11.17). Despite the new test’s advantages, the MMPI-2 is more established and is still more widely used. Typically, the tests are administered by computer. Although the MMPI was originally developed to assist in the clinical diagnosis of psychological disorders, it is now also used for occupational screening, such as in law enforcement, and in college, career, and marital counseling (Ben-Porath & Tellegen, 2008).

In addition to clinical scales, the tests also have validity and reliability scales. (Recall the concepts of reliability and validity from your study of psychological research.) One of the validity scales, the Lie Scale (or “L” Scale), consists of 15 items and is used to ascertain whether the respondent is “faking good” (underreporting psychological problems to appear healthier). For example, if someone responds “yes” to a number of unrealistically positive items such as “I have never told a lie,” they may be trying to “fake good” or appear better than they actually are.

Reliability scales test an instrument’s consistency over time, assuring that if you take the MMPI-2-RF today and then again 5 years later, your two scores will be similar. Beutler, Nussbaum, and Meredith (1988) gave the MMPI to newly recruited police officers and then to the same police officers 2 years later. After 2 years on the job, police officers’ responses indicated an increased vulnerability to alcoholism, somatic symptoms (vague, unexplained physical complaints), and anxiety. When the test was given an additional 2 years later (4 years after starting on the job), the results suggested high risk for alcohol-related difficulties.