Differential Personality Inventory–Form L (DPI)

Abstract

The Differential Personality Inventory–Form L (DPI), developed by Jackson and Messick in 1962, is a comprehensive psychological inventory designed primarily to measure personality traits that are indicative of underlying psychopathology. This extensive assessment tool consists of 300 items and is structured across 15 distinct scales.

The inventory is divided into two primary categories of measurement. Twelve scales focus on specific aspects of psychopathology, including Cynicism, Depression, Hostility, Irritability, Impulsivity, and Neurotic Disorganization. The remaining three scales are crucial validity measures: Defensiveness, Desirability, and Infrequency. The construction of the DPI utilized a rigorous sequential strategy aimed at achieving high scale homogeneity while simultaneously minimizing potential response bias. Early validation efforts (Jackson & Carlson, 1969) demonstrated strong psychometric properties, including internal consistency, convergent validity, and discriminant validity.

Keywords

Differential Personality Inventory–Form L, DPI, Psychopathology, Personality Measures, Test Validity, Jackson and Messick, Inventory, Somatic Complaints, Clinical Assessment

Authors

Jackson, Douglas N.; Messick, Samuel

Purpose

The principal purpose of the DPI is the systematic measurement and identification of specific personality traits and behavioral tendencies that serve as indicators of clinical psychopathology. It was designed as a diagnostic aid to classify individuals based on their propensity for maladaptive psychological functioning.

The scale’s structure allows clinicians and researchers to gain a nuanced understanding of various symptomatic expressions, ranging from overt hostility and rebelliousness to internalized issues such as depression and neurotic disorganization. Furthermore, the inclusion of three dedicated validity scales ensures the integrity and trustworthiness of the responses provided by the examinee.

Construct

The core psychological construct measured by the Differential Personality Inventory is Psychopathology. This construct is operationalized through 12 specific content scales, each tapping into a distinct dimension of maladjustment or clinical concern.

The scale assesses dimensions commonly associated with clinical disorders, such as affective disturbances (Depression), interpersonal conflict (Familial Discord, Hostility), cognitive and reality distortions (Psychotic Tendencies), and general neuroticism (Neurotic Disorganization). By measuring these specific components, the DPI provides a multifaceted profile of an individual’s psychological distress rather than a single global score.

Validity

The DPI has demonstrated evidence of both statistical and clinical validity, supporting its utility in differentiating between distinct populations. The sequential construction strategy used by Jackson and Messick was designed inherently to maximize the scale’s construct validity and minimize method variance.

Specifically, the DPI was assessed using a two-group discriminant analysis, comparing the responses of university students against those of reformatory inmates. This analysis revealed highly significant differences (p < .001) across 7 of the 12 primary content scales, strongly indicating that the inventory effectively differentiates between a normative population and a population characterized by higher rates of socially deviant behavior and psychological distress. Furthermore, the DPI has shown evidence of convergent validity and discriminant validity in separate studies.

Reliability

While the original source content does not explicitly provide specific reliability coefficients (e.g., Cronbach’s Alpha), the development literature confirms that the DPI exhibits strong evidence of internal consistency. This internal consistency was a direct result of the meticulous sequential scale construction method employed, which ensured that all items within a specific scale measured the same latent trait effectively.

The goal of achieving high scale homogeneity, a critical component of internal consistency, was prioritized during the initial development phases of the 300-item inventory. Further empirical research, such as that conducted by Jackson & Carlson (1969), supports the reliability of the DPI scales for research and clinical application, though specific quantitative measures of test-retest reliability were not detailed in the summary provided.

Factor Analysis

The provided source material does not indicate that a formal factor analysis was conducted or reported for the Differential Personality Inventory–Form L. While the scale development emphasized internal consistency and scale homogeneity via sequential strategy, the underlying factorial structure of the 12 content dimensions remains unspecified in the available documentation.

Instrument

Test Type: Inventory/Questionnaire

Format: The Differential Personality Inventory–Form L is a self-report instrument containing 300 items, typically administered in a paper-and-pencil format.

Language Available: English (United States)

Population Group: Adults

Age Group: Adulthood (18 years and older)

Population Details: The initial validation sample included university students and reformatory inmates located within the United States, providing a diverse group for psychometric comparison.

Test Methodology: The scale was constructed using a specific sequential strategy designed to optimize scale homogeneity and minimize the impact of response bias, such as social desirability or acquiescence.

Keywords

Differential Personality Inventory, Psychometric Assessment, Douglas N. Jackson, Samuel Messick, Internal consistency, Personality traits, Clinical inventory, Adult Assessment

Authors

Author ORCID Identifier: Not provided in source material.

Affiliation Email addresses: Not provided in source material.

Correspondence Address: Not provided in source material.

Permissions & Fee and Test Year

The instrument was first introduced in 1962 by Jackson and Messick. Information regarding current licensing, permissions, and associated fees is not available in the source data. Users should contact the copyright holders or relevant publishing bodies for current administration requirements.

Reference’s

• Carlson, K. A. (1972). Classes of adult offenders: A multivariate approach. Journal of Abnormal Psychology, 79(1), 84–93. https://doi.org/10.1037/h0032338
• Jackson, D. N., & Messick, S. (1962). Differential Personality Inventory. Unpublished manuscript.
• Jackson, D. N., & Carlson, K. A. (1969). The Differential Personality Inventory: A measure of psychopathology and social deviance. Unpublished manuscript.

Items of the Differential Personality Inventory–Form L (DPI)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

• Cynicism (e.g., “Most people are crooked.”)
• Depression (e.g., “I always feel insignificant.”)
• Familial Discord (e.g., “Some members of my family make my blood boil.”)
• Health Concern
• Hostility
• Impulsivity
• Irritability
• Neurotic Disorganization
• Psychotic Tendencies
• Rebelliousness
• Socially Deviant Attitudes
• Somatic Complaints