You'd have to be living a pretty isolated life to have missed the tension between Democrats and Republicans in the United States. These days, it seems like if a Democrat takes a position, you can be guaranteed that a Republican will immediately argue why that position is wrong and dangerous. And each statement by a Republican is immediately refuted by the Democrats.
It is as if Democrats and Republicans are perfect opposites. Is that something special about politics, or is it true of the way people think about opposing categories in general?
This question was addressed in a November 2010 paper in Cognitive Science by Evan Heit and Stephen Nicholson. They did a clever set of experiments. They started by generating a list of 15 public figures (like David Letterman, George W. Bush, Barack Obama, and Oprah Winfrey). People rated the people on this list for how typical they were of Democrats in general or how typical they were of Republicans in general. Psychologists often use these judgments of typicality to determine whether people think a particular item is a good member of a category.
Heit and Nicholson found that people's ratings were almost mirror images. That is when someone was rated as Typical of Democrats, the other group rated that same person as not at all typical of Republicans.
What was really surprising about this finding was the strength of this opposite relationship. When you characterize the relationship between two measures, you can use a statistic called a correlation coefficient. When two variables are not at all related, the correlation coefficient has a value of 0. When the variables are perfectly oppositely related, the coefficient has a value of -1, and when they are perfectly positively related, the coefficient has a value of 1. Psychologists are often excited about correlation coefficients that are larger than 0.5 or smaller than -0.5. The relationship in the typicality ratings for Democrats and Republicans was a whopping -0.996. That is, the ratings from different groups of people were nearly perfect opposites.
Perhaps this result is just a reflection of the way people treat categories in general. To check this out, the authors tried this study with other categories that were opposites. They had people rate the typicality of a number of foods as healthy foods or junk foods. Another group rated particular jobs as jobs for men or jobs for women.
The results for these other categories are both similar and dissimilar to the results for the political categories. The correlation coefficients for foods and jobs were still large and negative (-0.966 for foods, and -0.873 for jobs). So, people do tend to think of categories as opposites. However, in each of these sets, there were some items that were not at all opposites. For example, people thought that Teachers were a reasonably good job for both men and women. Similarly, Cheese was rated as a poor example of both a healthy food and a junk food.
Overall, then, when we have opposing categories, there is a general tendency to think that items are a good example of one or the other category, but not both. However, the modern political world has enhanced that tendency for political categories. That is, we not only categorize Democrats and Republicans as opposites we think of them as complete opposites.
This polarization is a real problem, because Democrats and Republicans are not really so different in many ways. Politicians generally want to make their country a better place. They want to see children get a good education. They want people to be protected and to be treated when they are sick. In the US, Democrats and Republicans differ in how they want to accomplish these goals. To the extent that we treated them psychologically as polar opposites, though, it will be harder for those politicians (and the people who support them) to see how they can have common ground to work on the difficult problems of governing a country.
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