Final answer:
A respected and directive leader is the factor that contributes to very cohesive groups. Authoritarian leadership style specifically creates a top-down communication pattern and can promote group cohesion.
Step-by-step explanation:
The factor that contributes to very cohesive groups is having a respected and directive leader. Cohesiveness in groups often comes from strong leadership where the leader sets the direction and maintains group harmony. Effective leadership fosters cohesive groups by providing guidance and encouraging members to work together towards common goals. Authoritarian leadership has a communication pattern that flows from the top down, which can sometimes contribute to group cohesiveness if the members respect and follow the leader. However, this style can also suppress individual opinions and lead to phenomena like groupthink, especially when the group is insulated and members prioritize harmony over critical analysis.
It's noted that different leadership styles, including democratic, authoritarian, and laissez-faire, can influence the group's dynamic and cohesion differently. An authoritarian leader is the most likely to create a top-down communication pattern and can have a significant impact on group cohesion if they are respected.