25. The Ya-Ya Sisterhood epidemic reveals the critical role that groups play in social epidemics. Psychologists tell us much the same thing: that when people are asked to consider evidence or make decisions in a group, they come to very different conclusions than when they are asked the same questions by themselves. Can we ever really make a decision in a vacuum, solely based on our own feelings, or do our peers or surroundings always influence us somehow?

26. The Rule of 150 suggests that the size of the group is another one of those subtle contextual factors that can make a big difference. Groups under the size of 150 are more effective as they can exploit the bonds of memory and peer pressure. Is there a particular group or organization that you consider successful and if so, what do you think makes them so effective?

27. If peer pressure is more powerful than the concept of a boss would you work harder for a boss whom you are friendly with because you care more what they think?