Despite the fact that many scholars have offered formal definitions of personality for almost 100 years, no consensus on any single definition has been achieved. In fact, a survey of 50 textbooks devoted to the study of personality would quite likely result in 50 distinct definitions of the term. Perhaps the reason that scholars have not agreed on a single definition is because of the broad scope encompassed by the notion of human personality. Clyde Kluckhohn and Henry A. Murray have suggested that human personality can be addressed at three distinct levels:

  1. How we are like all other people
  2. How we are like some other people
  3. How we are like no other people

At the broadest level, Kluckhohn and Murray’s framework suggests that there are some aspects of behavior that are common to all members of the human species. Murray, for example, in his classic taxonomy of needs, included a set of viscerogenic needs that are shared by all people. This category of needs, representing those things that humans need to survive, includes the need for air, the need for water, and the need for heat avoidance. Likewise, Abraham Maslow, in his specification of the hierarchy of needs, suggested that an individual’s psychological needs could not be addressed unless the basic physiological (e.g., food, water) and safety (e.g., security, avoidance of pain) needs were met.

At the second level—the way we are like some other people—Kluckhohn and Murray suggested that, when considering specific aspects of personality, individuals will share similarities with some but not all people. Within contemporary personality psychology, this level of personality description is where the notion of personality traits resides. Traits can be defined as characteristic behaviors, thoughts, and feelings of an individual that tend to occur across diverse situations and are relatively stable over time. A trait, once identified, is something that all people possess, but to differing degrees. For example, although all people can be described in terms of their extroversion, some people are outgoing and social, whereas others tend to be more introverted and reserved. Thus in a trait we can be said to be like some other people.

At the third level of personality description is how we are like no other people. This level of explanation includes those aspects of our personality that make us unique individuals. As such, this level includes the experiences we have had in our own histories that have shaped the way we think, feel, and act. In his writings about this level of personality description, Daniel P. McAdams has suggested that the goal of studying personality at this level is to understand individuals in the context of their personal life stories.

Idiographic versus Nomothetic Science

A debate has existed among personality scholars about the best approach for studying personality. Many scholars have argued that personality is best studied at the third level of Kluckhohn and Murray’s framework. Science at this level is idiographic, and knowledge of personality is gained through in-depth studies of particular individuals. However, other scholars have argued that personality is best studied at Kluckhohn and Murray’s second level. Science at this level is nomothetic, involving the study of general principles through the examination and comparison of many individuals. The debate over which of these approaches yields better information about the nature of human personality has, at times, been quite hostile. Although the debate has largely been argued in terms of methodological issues (i.e., the benefits and limitations of idiographic and nomothetic science), the heart of the argument is about the most appropriate level at which to understand personality. As such, the debate is in many ways pointless, because information from both levels of personality is necessary to develop a full understanding of the complexities of human personality.

Levels of Personality Description and Industrial/Organizational Psychology

All three of Kluckhohn and Murray’s levels of description are important for understanding human behavior in workplace contexts. For example, if a person’s basic needs are not being met, we might come to understand why the individual no longer appears to be driven for success at work. Likewise, if we were to know an individual’s personal history, we might better understand the person’s problems with authority from a supervisor. However, despite the applicability of the first and third levels of personality description, almost all applications of personality to industrial-organizational psychology are associated with the second level of personality description (i.e., how we are like some other people), and more specifically, with the notion of personality traits.

What Is a Trait?

There are two perspectives on the concept of personality traits. A first perspective is that traits are internal mechanisms that cause behavior. From this perspective, agreeableness, for example, is something within an individual that causes the person to behave in an agreeable manner. Hans J. Eysenck’s theory of extroversion is an example of this perspective. Specifically, he theorized that introverts have a higher baseline level of arousal than do extroverts. When placed in a social situation with considerable stimulation, the introvert (with an already high level of arousal) would be predicted to become easily over-aroused. In an attempt to reduce that overarousal, the introvert would engage in introverted behaviors, such as withdrawing from the situation. In contrast the extrovert, with a lower level of baseline arousal, would behave in an extroverted manner to obtain stimulation from the environment, thereby increasing the level of arousal (i.e., so as to avoid underarousal). According to Eysenck, then, the trait of extroversion is an internal biological process that causes behavior. Data have provided support for this internal mechanism approach to personality traits. Additionally, behavior genetic research, which has found that approximately 50% of variation in many traits can be explained by genetic influences, also points to a causal mechanism behind trait-related behavior.

A second perspective, typified by the act-frequency approach, is that personality traits are nothing more than descriptive categories of behavior. As such, a trait is a label for a set of related behaviors or acts. Acts that fall into the trait of sociability include talking to a stranger on an elevator, calling friends just to say hello, talking to coworkers in the hallway, or having a conversation with a clerk at a store. There could be hundreds of acts falling within this trait classification. A person with a high standing on this trait engages in this class of acts across situations more often than do other people. This approach is completely descriptive; there is no statement about the psychological processes that lead persons to behave the way they do. Although the acts people engage in may be caused by internal causal mechanisms, the act frequency approach does not specify those mechanisms.

The Structure of Personality Traits

Personality researchers have sought to develop a structure of personality traits for nearly 100 years. Much of this work has been based on studies of words in the English language, the so-called lexical hypothesis. The central idea of this hypothesis is that important aspects of human behavior will be encoded in the language. As such, it has been reasoned, a comprehensive understanding of personality traits can be derived from an examination of a language. The culmination of studies of the English lexicon is a structure of personality known as the Big Five. The Big Five taxonomy of personality is a hierarchical representation of the trait domain, with five broad traits representing the highest level of the classification structure. These five traits include the following:

  1. Neuroticism: Anxious, temperamental, nervous, moody versus confident, relaxed, unexcitable
  2. Extroversion: Sociable, energetic, active, assertive versus shy, reserved, withdrawn, unadventurous
  3. Openness: Intellectual, innovative, artistic, complex versus unimaginative, simple, unsophisticated
  4. Agreeableness: Trusting, trustful, helpful, generous versus cold, harsh, rude, unsympathetic
  5. Conscientiousness: Organized, neat, thorough, systematic, efficient versus careless, undependable, haphazard, sloppy

Although adversaries of the Big Five remain and have raised notable criticisms, the Big Five is the dominant perspective on the organization of personality traits within contemporary personality psychology.

It is expected that sets of more narrowly defined traits lie under each of these broad traits. For example, it has been proposed that the broad trait of conscientiousness can be broken down into more narrowly defined traits of dependability and achievement striving. Personality researchers, however, are far from reaching consensus on the precise number or nature of these narrowly defined traits at the next level of the hierarchy.

Compound Traits

Behavior is clearly complex, and many behaviors, especially those relevant to I/O contexts, are not a function of any single trait. Consistent with this line of thinking, more than one trait is often found to relate to particularly important work-related behaviors. In these cases researchers have proposed the notion of compound traits, which involve the combination of fundamental personality variables into a new personality variable that is capable of predicting a particular criterion. Perhaps the best known example of a compound personality variable is that of integrity. Research has demonstrated that scores on integrity tests—designed to be predictive of counterproductive employee behaviors—are notably related to the Big Five traits of conscientiousness, agreeableness, and (negatively) neuroticism. Thus the trait of integrity can be thought of as, at least in part, the confluence of these three Big Five dimensions. Other compound personality variables include customer service orientation and managerial potential. A unique aspect of compound personality traits is that they tend to result in criterion-related validities that are higher than those of the fundamental personality traits that compose them. Meta-analyses have shown, for example, that integrity tests tend to have greater predictive validity than do the individual traits of conscientiousness, agreeableness, or neuroticism.

Trait Personality and I/O Psychology

The role of personality within I/O psychology has had a rather tumultuous history. Today, however, personality is a topic of notable interest to both researchers and practitioners.


Much of the research on personality in I/O contexts has sought to identify whether and which personality traits are related in meaningful ways to important organizationally relevant behaviors. Primary research and subsequent meta-analyses have demonstrated that personality traits are related to such organizational behaviors as task performance, contextual performance, performance in training, job choice, leadership, job satisfaction, and perceptions of organizational justice, among others. This research has led to a better understanding of the personal characteristics associated with important work behaviors. For example, by studying how personality traits are associated with leadership, a better understanding of those individual characteristics associated with effective leadership has been developed.

Most research (and application) involving personality within I/O psychology is associated with the act-frequency approach to personality traits. A relationship between a personality trait and a criterion, as interpreted from an act-frequency perspective, suggests only that the behaviors associated with the trait classification are also important for the criterion. By way of example, an act frequency interpretation of a relationship between extroversion and leadership would suggest that some of the acts associated with the trait of extroversion are also associated with effective leadership. Although this research is certainly useful and informative, it is descriptive in nature; there is no identification or explication of the mechanisms through which personality traits cause organizationally relevant behavior.


The primary application of personality in I/O contexts is the assessment of personality traits for purposes of personnel selection. The goal of preemployment testing is to make inferences about an individual’s future behaviors in the workplace. Most assessments of personality traits for personnel selection are done through self-report questionnaires, but other methods can also be used to assess traits. If an applicant were to complete a self-report assessment of the trait of conscientiousness and receive a high score, an employer could surmise that this individual tends to engage in conscientious behaviors across situations and make the inference that the person will do so in the workplace as well. If the job requires behaviors that are associated with conscientious acts, this applicant could be desirable for the position. Meta-analytic research has shown that personality trait assessments can be predictive of job performance for a number of occupational groupings and across a range of performance criteria, with the strongest findings for the trait of conscientiousness.

When attempting to predict work-related behavior with personality trait assessments, care must be taken when choosing an appropriate criterion measure. The trait-situation debate taught personality researchers a great deal about what makes an appropriate criterion. The trait-situation debate arose when scholars began to argue that there was no consistency in behavior across situations. Research had shown, for example, that when children were put into various situations where they could behave honestly or dishonestly, the children did not behave in the same ways across situations. More specifically, a child who cheated on a test in one situation may turn in a lost dollar in another. This lack of observed consistency in trait-related behaviors across situations led these scholars to argue that traits were convenient fictions, and that situations were the stronger determinant of behavior. In further support of their point, these situationists argued that scores on personality trait assessments were not strongly related to observed behaviors. Although it took personality psychologists some time to respond to these arguments, they finally found their voice in the principle of aggregation. The principle of aggregation suggests that if behavior is considered across many situations, consistencies will emerge. These consistencies were interpreted as providing evidence in support of the existence of traits. Likewise, personality researchers argued that if behavior is aggregated across situations, scores from assessments of personality traits will be predictive of that aggregated behavior and will, in fact, account for as much variability in behavior as situations.

The lesson learned from the trait-situation debate and the resulting principle of aggregation is important for I/O psychology. Specifically, for personality to be predictive of organizationally relevant behaviors, those behaviors must be aggregated across situations. It will not be possible, for example, to predict whether an employee will be late next Tuesday on the basis of the conscientiousness score. It should be possible, however, to make a prediction regarding this person’s tendency to be late over the course of a year. In short, personality does not predict specific instances of behavior well, but it can predict lawful patterns of behavior. This is a point that I/O researchers and practitioners must keep in mind. There are several cases in the published literature where researchers have used a single instance of behavior as a criterion, and have, not surprisingly, failed to find the expected association between personality trait scores and the criterion measure.

Although personality trait assessments for purposes of personnel selection were traditionally administered in a paper-and-pencil format, it is becoming increasingly common for preemployment personality tests to be computer administered. Many companies are even beginning to use Web-based administrations, where a test taker can complete the test in an unproctored environment. Although research evaluating this mode of test administration is still emerging, initial evidence suggests that mean scores are similar between proctored and unproctored environments and that the criterion-related validity of the assessments is similar.


Personality is a broad field within psychology that has been studied at various levels, from single individuals to groups of people to people in general. Within I/O psychology, almost all work on personality has focused on personality traits, or stable tendencies to behave in certain ways. Personality traits have been found to relate to a wide variety of employee behaviors at work. An emerging notion is that of compound traits, or broad personality dimensions that are associated with several more fundamental personality dimensions and are predictive of important work-related behaviors. The primary application of personality to I/O contexts is preemployment testing, where scores on personality tests are used to make predictions about people’s future behaviors at work. When attempting to predict behavior from personality traits, it is essential for the I/O researchers and practitioners to keep in mind the principle of aggregation.


  1. Barrick, M. R., & Mount, M. K. (1991). The Big Five personality dimensions and job performance: A metaanalysis. Personnel Psychology, 44, 1-26.
  2. Buss, D. M., & Craik, K. H. (1983). The act frequency approach to personality. Psychological Review, 90, 105-126.
  3. Guilford, J. P. (1959). Personality. New York: McGraw-Hill.
  4. Hough, L. M., & Ones, D. (2001). The structure, measurement, validity, and use of personality variables in industrial, work, and organizational psychology. In N. Anderson (Ed.), Handbook of industrial, work, and organizational psychology (Vol. 1, pp. 233-277). Thousand Oaks, CA: Sage.
  5. McAdams, D. P. (1995). What do we know when we know a person? Journal of Personality, 63, 365-396.

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