Last year, I spent a lot of time on the bus. Sometimes this was a more pleasant experience, but whenever I came onto campus for a 9am lecture or left campus around 4 or 5pm, the buses were always packed. Often, when I got on there would already be people standing, so I would assume there must be no free seats and stand too.
However, halfway through the year I discovered something interesting. Buses that appeared to be standing room only often had loads of spare seats on the upper deck. If you push past the people standing and head upstairs, you can often find a free seat or ten. This discovery was great for me, but also very interesting when you consider it from a behaviour change perspective. If a bus has no free seats downstairs but no one standing, most people naturally check the upper deck. The moment even one or two people are standing however, almost no one checks the upper deck; people conform to the behaviour of others.
Solomon Asch (1951) investigated social norms and conformity in groups. In his experiments, one naïve participant would sit with a group of confederates. Each person would be asked in turn their answer to a simple line judgement task. When asked to complete the task individually, participants gave the correct answer almost 100% of the time. When put in a group where everyone else gave an incorrect answer, participants conformed and gave the same incorrect answer around a third of the time. In variations on this study, Asch found that a group as small as 3 produced nearly the same strength of effect as larger groups did. When someone gets on a bus to find that the people who got on before them are standing, this could also lead to social conformity: other people in the same position as you are standing, so you stand too.
Related to this is the theory of in-groups. People are more likely to conform to others if believe they are part of a group (e.g. Knippenberg & Wilke, 1992). Groups can be made very easily using very unimportant characteristics. Tafjel et al (1971) used a method called the minimal group paradigm, where people are split into groups based on a factor that has minimal importance, e.g. preference for one abstract artist over another. Even using this minimal group paradigm, people displayed an in-group bias. Therefore, having something in common as simple as being on the same bus at the same time may be enough to create a sense of an in-group, making people more likely to conform.
Using the information that others are standing to decide you should stand too is also an example of heuristic, or system 1 thinking. This means that people are making decisions using information easily available to them without using careful and effortful thinking. A particular example of this is a situation where people get off the bus from the upper deck, but people standing downstairs fail to realise that this means there are free seats they could use upstairs. People are using the standing behaviour of others to inform their own decision making, rather than using effortful, analytic, system 2 thinking to realise that they would be able to find a seat.
In conclusion, conforming to social norms is a powerful influence on behavior, but if you want a seat on a crowded bus you should break the social norm and go up the stairs!
Asch, S. E. (1951). Effects of group pressure upon the modification and distortion of judgments. In H. Guetzkow (Ed.), Groups, leadership and men; research in human relations (pp. 177-190). Oxford, England: Carnegie Press.
Bohner, G., Moskowitz, G. B., & Chaiken, S. (2011) The Interplay of Heuristic and Systematic Processing of Social Information. European Review of Social Psychology, 6, 33-68.
Knippenberg, D. V., & Wilke, H. (1992), Prototypicality of arguments and conformity to ingroup norms. European Journal of Social Psychology, 22, 141-155.
Tajfel, H., Billig, M. G., Bundy, R. P., & Flament, C. (1971). Social categorization and intergroup behavior. European Journal of Social Psychology, 1, 149-177.