Chelsea vs. PSG: Red card persuasion.

On Wednesday night, premier league giants Chelsea FC bowed out of the champions league, losing to Paris Saint Germain via the away goals rule. The game finished 2-2, but was overshadowed by the controversial dismissal of the PSG talisman Zlatan Ibrahimovic. The referee sent Zlatan off for a dangerous challenge on a Chelsea midfielder. Replays show that the tackle was not worthy of a red card, even prompting Chelsea manager Jose Mourinho to call for the European footballing body (UEFA) to rescind the red card. The referee made the decision to send the PSG player off after being bombarded by the whole Chelsea team. The Chelsea players persuaded the referee to show the red card by their collective influence. The following morning, back pages of national newspapers showed dismay at the way the Chelsea players, branding them as crying babies (see below).

Gerard, Wilhelmy, Conolley (1968) repeated Solomon Asch's classic 'line length' experiment (1951). In the original experiment, participants had to decide which of three lines (A, B or C) were the same length as a comparison line. On critical trials, confederates in the room purposely said the wrong answer. Most often, participants agreed with the majority - even if the majority group was obviously incorrect. Asch claimed that as long as the majority group had three members, the effect would stand with "full force" and increasing the number of members in the group would not amplify the conformity effect.

Gerard, Wilhely and Conolley (1968) note that Asch's claim about group size is not supported by any statistical analysis of trend. They repeat the line experiment using several numbers of confederates (1-7). The results display a positive linear relationship between group size and level of conformity (as measured by mean number of conformity induced errors). This relationship is displayed in figure 1.

The results demonstrate that the level of persuasion roughly increases with group size. Picture yourself as referee Bjorn Kuipers: eleven Chelsea players running at you screaming "send him off", is more persuasive than just one or two players. The above research supports this anecdotal hypothesis.

Although the Chelsea eleven managed to reduce PSG to ten, they couldn't capitalize and ended up missing out on a champions league last eight place.


References
          Ascir, S. E. Effects of group pressure, upon the modification and distortion of judgments. In II. Guetzkow (Ed.), Groups, leadership, and men. Pittsburgh: Carnegie Press, 1951. Pp. 177-190.

          Gerard, H. B., Wilhelmy, R. A., & Conolley, E. S. (1968). Conformity and group size. Journal of personality and social psychology, 8, 79-82.