False Dichotomy
The idea that people are either purely conservative or purely liberal is a false dichotomy. There may be a few individuals who fit the descriptions but most people have traits of both. The idea of pushing the left/right characteristics does more to confirm pre-set ideas than to show diversity. Most people tend to adapt their views based on what people around them talk about.
The problem with studies like this one is that people will use it to justify their prejudice as well as to use that prejudice against others. This is an example of creating catagories to put people in so that it appears to be scientific but is not.
Phrenology was the psuedo scientific study of the bumps on the skull. Some bumps were deemed to show criminal nature and others to show leadership. Phrenology was a big deal in the early 20th century but was found to be flawed and useless by mid century. Phrenology was an example of judging someone by a surface appearance rather than observing that person's behavior.
