Frequently Asked Questions About Personality Testing

When I was asked to blog for Psychology Today, I was told that this was because I had established some notoriety for my online personality test, posted at personal.psu.edu.

"All fine and good," I said, "but I have a wide range of professional interests, including evolutionary psychology and positive psychology, so I will want to blog about those topics, too. And I was told that this was fine.

Looking back over my posts over the past year, it seems to me that I've written very little about personality testing, so I thought it was about time I wrote on this subject. What I have decided to do is list a number of frequently asked questions that I get about personality testing, along with the kinds of answers I usually give to these questions. So, here we go:

What can you tell about a person from his or her answers on a personality test?

That depends on the scales the test contains. A personality scale shows your standing on one specific aspect of personality, relative to other people. For example, a short test containing a single shyness scale would indicate whether you are more shy, about as shy, or less shy than people in general. A longer personality inventory contains a set of scales designed to provide a more complete picture of personality.

In addition to showing where you stand on one or more scales, some personality tests will report research findings associated with your standing on the scale. For example, a report based on a shyness scale might mention that research has shown that people sometimes misinterpret shy behavior as conceitedness.

Exactly what traits does a personality inventory measure to give a complete picture of personality?

A complete portrait of personality covers five broad domains:

Extraversion - your amount of active engagement with other people;

Agreeableness - how pleasant and cooperative you seem to others;

Conscientiousness - your degree of reliability, self-control, and organized purposefulness;

Neuroticism - the frequency and intensity of negative emotions you experience;

Openness to Experience - your preference for intellectual and creative experiences versus traditional, practical activities.

All of the major personality inventories cover these five domains. Each inventory will focus on what the author believes are the most important specific aspects of the five domains. For example, the NEO Personality Inventory assesses six aspects of Agreeableness: Trust, Straightforwardness, Altruism, Compliance, Modesty, and Tender-Mindedness. The Hogan Personality Inventory measures five aspects of Agreeableness: Easy-To-Live-With, Sensitive, Caring, Likes People, and No Hostility.

Will a personality test reveal sensitive and potentially embarrassing information about me?

Personality tests typically assess general patterns of thoughts, feelings, and behaviors that are obvious to people who regularly come into contact with you. Any personality test used in personnel selection (and this includes all of the major personality inventories) must comply with fair employment practices legislation. Such tests avoid inquiring about physical disabilities and sensitive topics such as religious beliefs, sexual attitudes, drug use, and criminal behavior. Because personality tests assess relatively broad traits, they cannot detect specific, peculiar thoughts and habits unique to individuals.

Will a personality test show whether I'm crazy?

Most personality tests assess differences within the normal range of personality. Even an anxiety scale (or any scale related to psychological adjustment) measures normal differences in anxiety. Only highly specialized tests such as the Minnesota Multiphasic Personality Inventory (MMPI) are designed to diagnose psychopathology.

How do personality tests work?

Personality testing is based on two principles: self-report and self-presentation. Responses to some items can be seen as relatively direct, objective reports about yourself. Endorsing the item "I am well liked by those who know me" is a self-report about agreeableness. Obviously, an honest, self-perceptive person who endorses a lot of items like this will be seen by others as agreeable. Self-presentation involves endorsing items that indirectly lead others to form a certain kind of impression of you. For example, someone who endorses the item: "Everyone has some good qualities" is not providing a direct self-report of agreeableness, but nonetheless is more likely to be seen as agreeable than someone who does not endorse it.

What's to stop someone from lying on a personality test to create a certain impression?

Four responses can be made to this important question.

First, just as some people lie in everyday life, some people will lie on personality tests. Surprisingly, however, test-takers lie less often than you might think, even in highly evaluative situations such as employment selection. Although most people can skew their responses when instructed to do so, it has been estimated that only about one out of seven applicants tend to fake their responses during actual employment selection.

Second, just as some people are better liars in everyday life, some people are better fakers on personality tests. Successful faking for employment selection requires that the applicant determine (1) which traits are being used in hiring decisions and (2) how to answer items to elevate scores on the appropriate traits. Concerning Point (1), research has shown that for some occupations (e.g., manager), most people can determine which traits are used for hiring, but for others (e.g., truck driver), people have difficulty determining the relevant traits. Concerning Point (2), people can easily manipulate responses on obvious, self-report items, but social insight is required to manipulate the more subtle, self-presentation items.

Third, just like telling white lies, "faking" is not always undesirable. Research has shown that successful fakers are more socially insightful and perform better on certain tasks (including managerial judgment) than poor fakers. Also, research has shown that specific kinds of exaggerating or stretching the truth actually provide valid information about personality.

Finally, some of the longer, sophisticated personality inventories, such as the California Psychological Inventory (CPI), contain scales for detecting random responding and conscious attempts to look good or to look bad. Research with the CPI scales indicates that attempts to fake good will be screened out 64% of the time, attempts to look bad, 84% of the time, and random responding, 87% of the time.

I think my answers depend on the mood I'm in. On a different day I might be in a mood to answer some questions differently, so if my answers are always changing, how can they mean anything?

It's true that how you behave depends partly on how you feel at the present moment. But even though your feelings and moods fluctuate, they show consistent patterns. Items for personality tests are chosen to assess consistent patterns and therefore are not affected much by current mood. An exception might be if someone has suffered an extremely serious trauma such as the death of a loved one. Such serious traumas can invalidate responses to a personality test.

I noticed some items on the test that look very similar to earlier items. Is this a psychologist's trick for seeing how consistently I describe myself?

No. Similar items can be thought of as attempts to measure a particular trait several times to increase measurement accuracy. Just as a carpenter measures a piece of wood more than once before cutting, a personality psychologist measures a trait more than once with different items before drawing conclusions about a person's standing on the trait.

I'm not sure the results of my testing describe me correctly. Just how accurate is personality testing?

Accuracy depends to some degree on the amount of research underlying the test. A professional test author will write descriptions associated with different scores based on the way knowledgeable acquaintances have actually described people obtaining the score. The authors of self-assessment tests found in popular magazines more often base their interpretations on their own intuitions rather than on actual research findings.

Accuracy depends partly on the length of the test. Longer tests are generally more accurate than shorter tests. Ten items is about the minimum number of items for a reasonably valid personality scale.

Accuracy also depends on how precisely the test tries to categorize you. A test that tries to predict whether people perceive you as above average or below average on a trait will be correct about 70% of the time. A test that tries to predict more precisely whether people will perceive you as below average, average, or above average will be exactly right about 50% of the time, but will make extreme mistakes (identifying a below average person as above average or vice versa) only about 7% of the time. If you are uncertain about the accuracy of your test results, you should share them with people who know you well to get their views.