Human Stupidity: Historical: Group Reasoning II

Group decisions happen every day. We choose the people who will represent us in the government (in several countries, at least), we participate in groups of different sizes that have to reach an agreement about how to act (assuming a collective action does happen). Sometimes a group decision can be described as the sum of mostly independent decisions and actions, taken individually, as in an election. At other times, we assemble and discuss and the final estimate or the final action is decided as a result of the social process that happens between the assembled people. And, under different circumstances, a society may move in a direction that is just the consequence of how many individual actions interact with each other, with no real sense of group decision, except as a consequence of the sum of the behaviors and their interactions. One example of this is the fluctuation of prices as a consequence of the individual decisions of buyers and sellers. In this last case, all reasoning can be described as individual reasoning, while in the first two, decisions are made as a consequence of the sum of the opinions and, sometimes, the interactions between those opinions.


While the case of how the actions of people can influence the decision of the societies as a whole is very interesting (and I will return to it farther ahead), when we talk about the reasoning of a group, this is usually understood to be the first two cases. At this point, we will just discuss the cases where some reasoning is expected from the group, with or without interaction between its members.


After so many disappointments on our individual abilities, it makes sense to start with some good news. More than a hundred years ago, during the West of England Fat Stock and Poultry Exhibition, Francis Galton observed a contest where people attempted to provide the best guess for the weight of a fat ox . Of course, people proposed a range of different values, some close and some very distant from the true value (1,198 pounds). What surprised Galton was the fact that the median of the guesses was actually very close to the correct value at 1207 pounds. Later, he reported the average of the guesses was even closer to the real value, at 1,197 pounds!


This effect, where some average estimate provided by a group of people shows a remarkable agreement with reality was later coined as the Wisdom of Crowds. Galton associated this with the strength of a democratic government, where decisions arise from some kind of averaging over the opinions of many. Of course, the observation of one single case of a group estimate was not enough for a conclusion and several experiments were performed to test how well groups perform. In a 1982 review, Gayle Hill discusses the case of several papers published since Galton's initial observation. In her review, Gayle presented four different comparisons (in all cases, the results for groups included both groups working independently as well as groups where people were allowed to interact with each other): groups versus individuals, groups versus the most competent member, groups versus statistically pooled responses, and groups versus mathematical models. What she concluded from reviewing previous work was that, in the case of groups versus individuals, the groups tended to perform better, as expected. So, what happens when we examine the other possibilities (as well as other possible effects)?