Personality is a pattern of behaviour, thinking or emotion that is typical for an individual and fairly consistent across various situations. Psychologists tend to think of personality in terms of stable characteristics that are either biologically determined or acquired on a strong biological foundation, making it slow if not impossible to change. Personality tests measure such traits. Objective tests use a set of standardised rating scales, while projective tests require free responses to given stimuli.
In an objective personality test, the participant uses a set of scales or words for self-description. The details vary depending on the test, but there are usually statements describing behaviours, feelings and thoughts with which the test-taker has to agree or disagree. These raw results are coded, scored and then compared to statistically constructed norms. The results indicate how the person compares to others on a particular characteristic.
Popular objective personality tests include the Minnesota Multiphasic Personality Inventory, or MMPI; Millon Clinical Multiaxial Inventory, or MCMI-II; Myers-Briggs Type Indicator; 16PF Questionnaire; Newcastle Personality Assessor, or NPA, and Eysenck Personality Questionnaire.
Standardisation: Objective Advantage
One of the main advantages that objective tests have over projective tests is standardisation. This means they are fairly easy and thus cheap to administer. The scoring doesn't depend on who is doing the scoring, so there is no bias in results. The basic interpretation of objective tests doesn't require a trained psychologist. Sometimes even a computer can do that. The most popular objective personality tests have been extensively tested and have well-established norms, so it's possible to interpret people's scores statistically in comparison to the general population. Many of the objective tests have good grounding in psychological theory.
Validity and Reliability: Objective Advantage
Most importantly, objective personality tests are fairly reliable and have overall higher validity than projective tests. A reliable test measures consistently. If a test is reliable, the same person should obtain the same or very similar scores on different days. A valid test measures what it is supposed to measure. The scores of a test with a high validity correlate with behaviour and allow for its prediction. A valid test of extroversion would produce scores that have positive associations with social behaviour. Although the correlations with behaviour are fairly low, even for the objective tests, they are better than for the projective tests.
Limitations of the Concept of Personality: Objective Disadvantage
The main disadvantages of objective personality tests have to do with the concept of personality. Some psychologists, including Walter Mischel, point out that behaviour is largely situation dependent and that even the best personality tests don't predict behaviour or real-life outcomes very well.
Lack of Subtlety: Objective Disadvantage
Many objective tests have been created to screen for mental disorders, MMPI being the most significant example, but companies use them now to asses people for work purposes. In clinical diagnosis, however, objective tests are a very rough tool that doesn't allow for subtle differentiations. They tell the clinician nothing about the individual experiences and inner workings of the patient's mind. Many clinicians like projective tests as they are less restrictive and more subtle, especially when interpreted individually and not "scored" in the manner of objective tests.
Lack of Individual Context: Objective Disadvantage
Objective tests, ostensibly, don't rely on the content of the question but on statistical association. In principle, it doesn't really matter whether somebody really is "almost never late for his appointments"; what matters is that, generally, people who say "yes" to this statement are more likely to behave in a certain way. This particular association, however, might not exist at all for that particular person.
Easy to Fake: Objective Disadvantage
Objective tests are easier to fake then projective tests. Although many incorporate questions that check for lying and a tendency to give socially acceptable answers, most of them are easy to spot, especially for intelligent and motivated people, for example, in a job-recruitment context.
Objective tests are acceptable tools for personality assessment, especially for scientific purposes. They are economical to use and provide standardised scores that allow researchers to compare groups of people effectively. As research instruments, they have good reliability and better validity than projective tests. They also might provide some indication of the strengths and weaknesses of particular individuals, but they should be treated as a supporting tool only. Projective tests work best as subtle, qualitative instruments of clinical diagnosis that every clinician interprets according to his experience. A projective test is an enabling technique first and foremost, rather than a test in a quantitative, statistical sense.