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Personal Inventories:

A personality inventory is essentially a questionnaire in which the person reports reactions of feelings in certain situations. It resembles a very set or standardized kind of interview. A personality inventory asks the same questions of each person, and the answers the usually, given a form that can be easily scored-often by machine. A personality inventory may be designed to measure a single dimension of personality (such as introversion-extraversion) or it may measure several personality traits simultaneously, resulting in a profile of scores.

Different strategies have been used in contracting personality inventories.

a. Personality Profiles:

The Sixteen Factor Personality Questionnaire, whose results are shown in figure is based on factor analysis. By factor analyzing the trait description of many individuals, the author of this questionnaire isolated 16 factors as the basic personality traits. He then devised questions is measure each of them.

For example, answering “No” to the question “Do you tend to keep in the backgrounds on social occasions?” would earn you a point toward the dominant side of the E factor. Note that the factors themselves are nameless statistical quantities; they cold must as well be called A, B, C and so forth, which is the way they were initially labeled.

The trait names that were given to the factors are simply the experimenter’s best guess as to what a particular factor represents, based on the data that contribute to it and the real-life behavior with which its correlates.

Each factor in figure is given two names: one for a high score and another for a low score. By plotting an individual’s test score for each of the factors, we arrive at a personality profile-a kind of shorthand description of the individual’s personality.

The black profile in figure shows the average test scores for a group of airline pilots while, the red and gray profiles give the average scores for a group of artists and a group of writers. We can see that artists and writers, as a group, differ significantly from pilots on a number of personality traits.

b. MMPI:

Another personality inventory, the Minnesota Multiphasic Personality inventory (referred to as the MMPI) is based on the method of empirical construction rather than factor analysis. Instead of assuming specific personality traits and designing questions to measure them, many items were given to well-defined groups of individuals who were known to differ from the norm on some external criterion. Only those questions that discriminated significantly between group were retained to form the inventory.

For example, to develop a scale of items that will distinguish between schizophrenic and normal individuals, the same series of questions are given to two groups: the criterion group consists of patients hospitalized with a diagnosis of schizophrenia; the control group is an equal number of individuals who have never been diagnosed as having psychiatric problems.

Only those test items that discriminate significantly between the two groups are retained for use in a scale for measuring schizophrenia. Questions that at face value might seem to distinguish normals from schizophrenics (e.g., “I feel as if I am not a part of the word”) may or may not do so when put to the test. The method of empirical construction contrasts the responses of two distinct groups to ensure that the test item bears an actual (empirical) relationship to the personality characteristic being measured.

Initially, the MMPI was developed to aid clinicians in the psychiatric diagnosis of abnormal personality types. The test is composed of some 550 statements (about attitudes, emotional reactions, physical and psychological symptoms, and past experiences) to which the subject answers “true”, “false”, or “cannot say”, Some of the items are:

My mother or father often made me obey even when I thought it was unreasonable. At times my thoughts have ahead faster than I could speak them.

The responses are scored according to the correspondence between the answers given by the subject and those given by patients with different kinds of psychological disturbances.

Since, the MMPI is derived from differences between criterion groups, it does not really matter whether what the person says about himself is true of not. The fact that he say it is important. If all schizophrenics answer true and all normal subjects false to the statement “My mother never loved me”, their answers distinguish the two groups, regardless of how mother actually behaved.

This is one of the advantages of a test based on the method of empirical construction as opposed to one where the test constructor assumes that certain answers indicate certain psychological disorders. Answering true to the statement “I think that most people would lie to get ahead” might be assumed to be a sign of paranoia. When this item was included in the MMPI it was found that patients diagnosed as paranoid were significantly less apt to respond true to this statement than normal individuals.

Although, the original MMPI scales were derived from comparison groups suffering from personality disorders often severe enough to require hospitalization, they have been widely used in the study of other populations. One of these studies, illustrated in compares the scores of male delinquents and nondelinquents.

Rating Scales:

Unless the individual is motivated to answer honestly in a personality inventor, he can bias his responses so as to appear “sick” (e.g.), if he wants to avoid military service or be eligible for a disability pension) or to appear more efficient and well adjusted tan he really is (e.g., if he is applying for a job).

And even the person who is trying to be as accurate as possible may have traits and tendencies of which he is unaware. Various devices have been incorporated into personality inventories to compensate for the individual’s “test-taking attitude” but, none have proved completely satisfactory.

One way to avoid this problem is to have someone else evaluate the individual, either on the basis of what they know or by observing him in certain situations. To put this kind of judgment into a standardized form, rating scales are used. A rating scale is a device for recording judgments.

In order for the rating to be meaningful, the rater must (1) understand the scale; (2) be sufficiently acquainted with the person being rated so that meaningful judgments can be made; and (3) avoid the “halo effect”-the tendency to rate a person in a favorable direction on all traits because of a good impression made on one or two (or, conversely, to rate unfavorably because of a poor impression made on one or two traits).

Unless the rater knows the person being rated fairly well, or the behavior being rated is very specific, ratings may be influenced by social stereotypes. That is, the rater may base his ratings as much on how he believes a “suburban housewife”, a “long-haired intellectual”, or a “high school athlete” acts and thinks as on the actual behaviours of the subject being rated.

Despite such problems, descriptions of a person provided by different raters in different situations often yield good agreement. In one study, for example, the aggressiveness of a group of school boys between the ages of eight and twelve was rated by their peer and by observers who watched them playing games in the school yard. There was close agreement between the two sets of ratings (Winder and Wiggins, 1964).