How do people choose to vote for someone in a presidential primary? While one of the most traditional criteria is ideological similarity, there is something even more fundamental: electability. While the whipsawing nature of the current primary cycle has made this a bit harder to discern, many voters choose to vote for the most electable candidate. And despite this somewhat overly simple and circular criterion, it is not vacuous. In fact, it is similar to something known as a Keynesian beauty contest.

A Keynesian beauty contest is a hypothetical beauty contest where people are asked to choose the most beautiful of a selection of women. Those who chose the most popular choice are then eligible for some sort of prize, such as being entered into a raffle. So, while many will just choose the woman they deem the most beautiful, others will think a level or more deeper: They will choose the woman who is most likely to be chosen the most beautiful by others.

This is often what happens in primaries, as was noted during the 2004 Democratic primaries. According to this logic, a Keynesian presidential primary will then result in a choice that is the collective wisdom, though it's not always all that wise. As Pietra Rivoli, a Georgetown professor, told Planet Money, "The key danger is that nobody's really thinking." People are simply looking to everyone else. In fact, when Planet Money tested this, using videos of cute animals, the voting on videos that were thought to be cute by everyone else was more skewed than the voting for the videos people themselves thought were cute.

This kind of contest is similar to other sorts of questions, such as how people might respond to this survey on Slashdot:

The most well-known and elegant version of this question, used to reduce aspects of the Keynesian beauty contest to elegant game theory, is where contestants must guess a number between 0 and 100 that is two-thirds of the average of everyone else's responses. Since lower numbers are more likely to be correct in being two-thirds of the average, game theory dictates that the optimal answer should therefore be zero.

However, people don't actually think this way. When this competition is tried in the "real world" the winner is never zero. For example, a Danish paper, when trying this contest, had nearly 20,000 entrants, and the winning response was 21.6. You can even try this yourself here, playing against the 100 most recent players, where the winner is greater than zero.

So, what does this mean for primaries? Even though there are optimal strategies for anticipating others' choices, we are far often from optimal, making choices that are not entirely logical and are dependent themselves on others' irrational decisions. And this could perhaps explain at least some of the current volatility in this primary cycle.

Top Image: Amanda Wood/Flickr/CC-licensed