Explaining this may be a complicated matter, but Nosek has put forth a pretty decent theory. He believes that a lower cognitive capacity makes people more attracted to simplifying ideologies. On the surface it certainly seems to make sense. Some of the findings by Brock University are quantified in the chart plotting mean adolescent intelligence against adult political ideology.
|IQ vs Political Orientation|
Now a professor from the University of Arkansas has echoed these sentiments, albeit in a slightly different study. This study, published in the journal "Personality and Social Psychology Bulletin", focused it's efforts on what is described as "low-effort" thinking. According to Dr. Scott Eidelman, the study's lead author, "People endorse conservative ideology more when they have to give a first or fast response." Eidelman cautions that while low-effort thinking promotes political conservatism it may not be the case that political conservatism necessarily promotes low-effort thinking.
The interesting part of these studies isn't that a relationship between IQ and political orientation exists, but why it exists. The answer to that conundrum awaits further studies.