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The Personality Laboratory at the University of New Hampshire

  wrought iron letters: UNH  
About the Laboratory:site homepeople in the lablist of laboratory publicationsselected reprints
Overview of Selected Theoretical Work: personality as a scientific discipline the Systems Framework for personalitypersonal intelligence emotional intelligence ethical commentary on the personality of public figures

Psychological Measures and Procedures: scales of mood,• mood-congruent judgment,• empathy, • meta-experience of mood, • personal intelligence emotional intelligenceintellectual experience • and experimental procedures

Other Resources: links to documents, video and websites on personalityUNH Department of Psychology (New Window)

What Are "Parts of Personality"?

A part of personality can be defined as follows:

A part of personality is a discretely identified, localized portion of the personality system that performs a unique function, stores information, or represents a thematic quality of the individual’s mental processes (after Mayer, 1995, pp. 828-829).

To get a better sense of what is meant above, each key part of the definition can be further described:

...personality... -- The system that represents the collective function of major psychological subsystems such as motives, emotions, cognitions, the self, and similar such aspects.

…discretely identified... -- That is, using sound analytic and conceptual rules, it makes sense to identify various discrete subsystems of personality. The part is not necessarily a discrete part of the brain or mind, although that is the intention, but nonetheless can be divided for purposes of scientific exploration.

…localized portion of the system... -- It is a portion or component of the system, and not the whole system.

…that performs a unique function... -- That is, some parts of personality are responsible for doing something that affects the operation of the personality system (e.g., short-term memory).

stores information…  -- That is, some parts of personality store information about the self and the world (e.g., knowledge about baseball).

...represents the thematic quality of personality processes... -- That is, some parts of personality represent identified thematic aspects or patterns of personality function (e.g., an expert in baseball).

Personality parts (or components) can be distinguished according to two broad fashions: according to their type, and their function (see Mayer, 1995).

Four Types of Personality Parts

Types of personality parts are distinctions among parts of personality according to their internal construction or nature. When we talk about personality traits, or mental models, or mental mechanisms, we are talking about types of personality parts. These types are important to know about because they allow personality psychologists to compare one part of personality to another, and to discuss groups of personality parts that might be similar from one functional area of personality to another. Four major types of personality parts are mental mechanisms, mental models, traits, and agencies (from Mayer, 1995, ; Mayer, 1998, pp. 126-129).

Mental mechanisms. Mental mechanisms perform basic psychological functions necessary to the operation of more complex aspects of personality. They employ multiple smaller operations, often at a psycho-neurological level to perform their task. Examples of mental mechanisms include working memory, facial expressions of a specific emotion, and motivational urges.

Mental models. Mental models are representations (e.g., connected information), about a particular topic or subject. The subject of mental models often involves aspects of the self (e.g., self-concept in regard to spelling), and aspects of the world (e.g., beliefs about the Red Sox baseball team). As these examples suggest, mental models include not only cognitive information, but also feelings and motives in regard to the particular topic.

Traits. Traits are multiple, thematically-related personality features that collectively reflect the operation or characteristic functioning of a particular area of personality. For example, the trait of intelligence describes the level of functioning of broad areas of the cognitive system. As another example, extraversion describes the functioning of broad areas of the motivational and social areas of personality. The "multiple, thematically-related features" portion of the description indicates that traits typically emerge from many diverse contributors. Extraversion, for example, represents the collective expression of lively, positive emotions (one feature), along with social knowledge (another feature), and a motive to be with others (yet another feature).

Agencies. Agencies perform an extensive set of the functions of personality itself, but in partial independence of the whole, and are lacking in the complex integrated properties of the whole personality. Agencies combine many mental mechanisms, mental models, and traits together. Examples of agencies are Freud's (1923) id, ego, and superego, as well as Epstein's (1988) Experiential mind.

Four Functional Areas of Personality Parts

After recognizing the various types of personality parts, one can divide them into the functional areas to which they pertain. For example, if we identify a motivational area of personality, the parts related to bringing about motivations can be clustered in that area, along with other parts that describe functioning in that area. [More forthcoming, but to see the four areas of personality structure now, see the page on The Systems Set.]


Freud, S. (1923/1960). The ego and the id. J. Riviere (Trans.), J. Strachey (Ed.). New York, NY: W. W. Norton.

Epstein, S. (1998). Constructive thinking. New York, NY: Praeger.

Mayer, J. D. (1995). A framework for the classification of personality components. Journal of Personality, 63, 819-877.

Mayer, J. D. (1998). A systems framework for the field of personality psychology. Psychological Inquiry, 9, 118-144.

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