Midlife Development Inventory

Abstract

The Midlife Development Inventory (MIDI) Personality Trait Scales represent a crucial psychometric tool utilized in large-scale developmental research, notably the MacArthur Foundation Research Network on Successful Midlife Development (MIDUS). This instrument is designed to comprehensively assess key dimensions of personality among middle-aged adults. The MIDI scales extend beyond the traditional Big Five personality traits model by incorporating an additional factor, Agency, resulting in a six-factor structure. The scale construction was detailed in a 1997 technical report, providing researchers with a reliable and valid measure of individual differences in dispositional characteristics during this critical life stage.

Keywords

Midlife Development Inventory, MIDI, Personality psychology, Big Five, Neuroticism, Extraversion, Agency, Psychological Assessment, Life Span Development.

Authors

Margie E. Lachman, Suzanne L. Weaver, O. R. Burack

Purpose

The primary purpose of the MIDI Personality Trait Scales is to provide a standardized, robust measure of personality characteristics that are pertinent to research on aging and adult development. This scale allows researchers to examine how stable personality traits influence various outcomes across the adult lifespan, including physical health, psychological well-being, social relationships, and the sense of control. The instrument is specifically tailored for use within the context of extensive longitudinal studies focusing on the complexities of the midlife period.

The inclusion of the Agency dimension, alongside the standard Big Five personality traits, allows for a more nuanced understanding of how individuals interact with and attempt to shape their environment. This measure is essential for investigating developmental trajectories and the maintenance of successful functioning during the transition from early to late adulthood.

Construct

The MIDI Personality Scales are structured around a six-factor model of personality psychology. This model integrates the globally recognized dimensions of the Five Factor Model (FFM) with a unique factor known as Agency. The six constructs measured are:

• Neuroticism: Reflecting emotional instability, anxiety, and worrying.
• Extraversion: Characterized by sociability, assertiveness, and energy.
• Openness to Experience: Measuring creativity, intellect, and breadth of interests.
• Conscientiousness: Pertaining to organization, responsibility, and thoroughness.
• Agreeableness: Relating to warmth, helpfulness, and sympathy.
• Agency: Representing self-confidence, forcefulness, and dominance—a measure often associated with personal control and mastery.

Validity

While specific psychometric documentation detailing all facets of validity (e.g., predictive, concurrent) is extensive across the MIDI literature, the scale demonstrates strong construct validity due to its consistent alignment with the widely accepted Big Five personality traits framework. The scale items are specifically selected to be relevant to the life challenges and social roles experienced during midlife. Furthermore, the instrument’s continued use in major epidemiological and longitudinal studies, such as MIDUS, confirms its utility and empirical soundness in capturing meaningful personality variance.

Reliability

Internal consistency reliability was assessed using Cronbach’s alpha coefficients, demonstrating acceptable to strong reliability across most dimensions. The reliability values reported in the source content are:

• Agreeableness: (alpha 0.80)
• Extraversion: (alpha 0.78)
• Openness to Experience: (alpha 0.77)
• Neuroticism: (alpha 0.74)
• Agency: (alpha 0.79)
• Conscientiousness: (alpha 0.58)

It is important to note the relatively lower internal consistency reported for the Conscientiousness scale (alpha 0.58). Despite this lower value, the majority of the scales exhibit strong reliability, confirming their ability to consistently measure the intended personality constructs within the midlife sample.

Factor Analysis

The development of the MIDI Personality Scales involved factor analytic techniques to ensure that the individual trait items grouped statistically into the intended six underlying dimensions. The analysis confirmed the hypothesized structure of the Revised MIDI Personality Scales, distinguishing the five traditional FFM factors and the distinct factor of Agency. This six-factor solution confirms the scale’s theoretical basis and its suitability for measuring both dispositional traits and characteristics related to behavioral control and self-efficacy, which are highly relevant in midlife research.

Instrument

Test Type: Self-report Psychometrics inventory of personality traits.

Format: A 4-point Likert-type scale is used for responses. The response options are: 1-A LOT, 2-SOME, 3- A LITTLE, 4- NOT AT ALL.

Language Available: Primarily English (as developed for the MIDUS study).

Population Group: General adult population, specifically those engaged in large-scale developmental studies.

Age Group: Adults, particularly focusing on the midlife age range (typically 35 to 65 years).

Population Details: Originally developed using data from the MacArthur Foundation Research Network on Successful Midlife Development (MIDUS) sample in the United States.

Test Methodology: Self-administered questionnaire where respondents rate how much each trait adjective describes them.

Keywords

MIDUS, Psychometric Assessment, Personality Traits, Cronbach’s alpha, Self-Report, Adult Development, Lachman.

Authors

Author ORCID Identifier: Not provided in source material.

Affiliation Email addresses: Not provided in source material (Primary affiliation is Brandeis University).

Correspondence Address: Not provided in source material.

Permissions & Fee and Test Year

The MIDI Personality Scales are generally available for academic and research use, particularly within the context of the MIDUS project. Researchers often utilize these scales free of charge, provided proper citation is given to the original developers. The scale construction and scoring details were formally documented in a technical report published in 1997.

The original PDF of the instrument can be downloaded here: http://www.brandeis.edu/departments/psych/lachman/pdfs/midi-personality-scales.pdf

Reference’s

• Lachman, M. E., & Burack, O. R. (1993). Planning and control processes across the life span: An overview. International Journal of Behavioral Development, 16, 131 – 143.
• Lachman ME, Weaver SL. Technical report. Brandies University; Waltham, MA: 1997. Midlife Development Inventory [MIDI] Personality scales: Scale construction and scoring. The original PDF can be downloaded here: http://www.brandies.edu/departments/psych/lachman/pdfs/midi-personality-sclaes.pdf
• Lachman, M. E. & Weaver, S. L. (1998). Sociodemographic variations in the sense of control by domain: Findings from the MacArthur studies of midlife. Psychology and Aging, 13, 553-562.
• Lachman, M. E. & Weaver, S. L. (1998b). The sense of control as a moderator of social class differences in health and well-being. Journal of Personality and Social Psychology, 74, 763-773.

Items of the Midlife Development Inventory

MIDI Personality Trait Scales

Revised MIDI Personality Scales

a) Outgoing

b) Helpful

c) Moody

d) Organized

e) Self- confident

f) Friendly

g) Warm

h) Worrying

i) Responsible

j) Forceful

k) Lively

l) Caring

m) Nervous

n) Creative

o) Assertive

p) Hardworking

q) Imaginative

r) Softhearted

s) Calm

t) Outspoken

u) Intelligent

v) Curious

w) Active

x) Careless

y) Broad-minded

z) Sympathetic

aa) Talkative

bb) Sophisticated

cc) Adventurous

dd) Dominant

ee) Thorough

The scoring key assigns items as follows (based on the original 4-point scale):

• Neuroticism (alpha 0.74): (c, h, m, s)
• Extraversion (alpha 0.78): (a, f, k, w, aa)
• Openness to Experience (alpha 0.77): (n, q, u, v, y, bb, cc)
• Conscientiousness (alpha 0.58): (d, i, p, x)
• Agreeableness (alpha 0.80): (b, g, l, r, z)
• Agency (alpha 0.79): (e, j, o, t, dd)