This paper investigates how unitizing affects external observers' annotation of group cohesion. We compared unitizing techniques belonging to these categories: interval coding, continuous coding, and a technique inspired by a cognitive theory on event perception. We applied such techniques for sampling coding units from a set of recordings of social interactions rich in behaviors related to cohesion. Then, we compared the cohesion scores the observers assigned to each coding unit. Results show that the three techniques can lead to suitable ratings and that the technique inspired to cognitive theories leads to scores reflecting variability in cohesion better than the other ones.