Interpersonal similarity and synchrony effects on group cohesion during a shared emergency stressor

Perceptions of group cohesion are a protective factor in high-stress contexts, yet little is known about what shapes cohesion in ad-hoc groups during an acute shared stressor. Interpersonal similarity and synchrony have been established as antecedents of cohesion, but their role in civilian dominant ad-hoc groups during emergencies remains unclear. We addressed this with 113 healthy adults (62.5% female; 67.5% White; Mage: 31.5, 20-55 yrs) assigned to dyads (two people) or small groups (three to nine people). Groups completed multiple simulated emergency evacuations through a maze. Participants reported emotions before and after each emergency and later rated their perceptions of social and task cohesion. We hypothesized that individuals that were more similar to their group, individuals with greater emotional synchrony, and individuals in dyads would predict greater perceptions of social and task cohesion. In partial support of our hypotheses, sex similarity and extraversion similarity were positively associated with perceptions of social cohesion. Emotional synchrony did not predict perceptions of cohesion. As expected, individuals in dyads perceived more social and task cohesion than those in a small group. These findings highlight the role of group composition in shaping perceptions of group cohesion in ad-hoc groups during emergency scenarios.