Getting Even or Being at Odds? Cohesion in Even‐ and Odd‐Sized Small Groups

We propose that even‐sized small groups often experience lower cohesion than odd‐sized small groups. Studies 1 and 2 demonstrate this effect within three‐ to six‐person groups of freshman roommates and sibling groups, respectively. Study 3 replicates the basic even/odd effect among three‐ to five‐person groups in a laboratory experiment that examines underlying mechanisms. To account for the even/odd effect, Study 3 focuses on the group's ability to provide members with certainty and identifies majority influence as the key instrument. We argue that groups struggle to provide certainty when they lack majorities (e.g., deadlocked coalitions) or contain unstable majorities (i.e., where small changes in opinion readily overturn existing power arrangements). Member uncertainty mediated the effects of coalition structure on cohesion. The results link structural variables (i.e., even/odd size and coalition structure) to psychological outcomes (i.e., member uncertainty and relational outcomes).