Forms, Importance, and Ineffability of Factor Interactions to Define Personality Disorders

Area of Science:

• Psychology
• Clinical Psychology
• Personality Psychology

Background:

• The emergent interpersonal syndrome (EIS) approach views personality disorders as trait interactions.
• Empirical application of EIS to psychopathy has encountered difficulties in identifying significant interactive predictors.
• Existing research highlights challenges in detecting small interaction effects within complex trait models.

Purpose of the Study:

• To detail the difficulties encountered when applying the EIS approach to psychopathy.
• To investigate the variance explained by trait interactions in predicting interpersonal outcomes.
• To determine the sample size requirements for detecting EIS interactions with adequate statistical power.

Main Methods:

• Utilized empirical work on psychopathy, focusing on uncorrelated traits to maximize statistical power.
• Analyzed the variance explained by interactions between constituent traits relative to main effects.
• Considered sample size requirements for achieving 80% power with a .05 false positive rate for interaction effects.

Main Results:

• Trait interactions within the EIS framework explained small amounts of variance in interpersonal outcomes, relative to main effects.
• Detecting these interactions necessitates large sample sizes, potentially around 1,000 observations, for adequate power.
• Effect sizes diminish with the analysis of higher-order trait interactions, complicating model specification.

Conclusions:

• The EIS approach requires precise specification of which trait interactions constitute a specific syndrome.
• Researchers must consider interaction types (ordinal, disordinal, nonlinear) when designing studies for EIS.
• Efficiently modeling EIS interactions necessitates careful consideration of study design, sampling, and analytical strategies.