Affiliation: A Consequential, Interstitial Trait

Although development and maintenance of relationships is an essential part of mental health and well-being and nearly universal among humans, people vary in their tendency to affiliate with others. Affiliation represents an interstitial personality trait falling between the Compassion aspect of Agreeableness and the Enthusiasm aspect of Extraversion. Though interpersonal behavior has been studied extensively, the field lacks validated questionnaires measuring individual differences in Affiliation. Here, we document the construction and validation of a new Trait Affiliation Scale. Data were taken from six samples (ntotal = 27,198). Study 1 focuses on scale creation, including identification of 24 candidate items and initial tests of convergent validity. Study 2 focuses on scale refinement including the application of item response theory to create a ten-item scale. Study 3 investigates reliability and construct validity. Study 4 provides evidence of test-retest reliability in a four-wave longitudinal dataset. Finally, Study 5 provides evidence for criterion and incremental validity, testing associations of affiliation with outcome variables (e.g., social behaviors, social network size, social cognition, and affiliative states) above and beyond Agreeableness, Extraversion, and their aspects. We discuss the importance of affiliation as a trait and provide recommendations for future research using this new scale.