Why do apparently disparate beliefs clump together?

Human activity is causing a gradual warming of the earth’s atmosphere.

Those convicted of crimes should be incarcerated.

Gay marriage is morally wrong and should not be permitted.

Private enterprise is intrinsically more efficient than government agencies.

These are four disparate claims which appear to have little to do with one another. Gay marriage, for instance, has little to do with Global Warming – at least as far as my limited imagination can see. Incarceration of criminals has little to do with the efficiency of private enterprise. Yet, how one feels about these four statements will tend to identify you with one group or another.

This is anecdotal, I admit. I have not seen a quantification of these beliefs. Nonetheless, it is my impression that beliefs clump together. Specifically, if a person is anti-gay marriage, a global warming denier, and believes that we should lock the guilty bastard up, I will wager that this person also believes that private enterprise is intrinsically more efficient than government. This is because it is my impression that the political right is where you are more likely to find opposition to gay marriage, etc.

Why does social conservatism walk hand in hand with fiscal conservatism? 

For simplicity I have chosen the right v. left but there are many circles you could draw around many groups: religious zealot, atheist, cab driver, bartender, art student, Caucasian, African American, Serbian, Canadian, etc. Why do beliefs clump? Why do people in a particular group often share a similar basket of beliefs even though there is no logical connection between the beliefs?

There are a few reasons I can think of but, honestly, I don’t know. It puzzles me.

Perhaps the group informs the belief. A person is attracted to the political left because they believe that government should be an invasive force of good. Once they arrive the other members of the group convince them to believe in global warming and gay marriage. Sort of the Borg. A hive mentality. One belief causes you to enter the hive, once there you are sucked into the collective intelligence of the group and come to believe as the other members of the group do.

Perhaps some groups are actually smarter than others. Beliefs are correct or incorrect – true or false. And, perhaps, some groups are better at correctly answering the questions. Listening to Question Period in Parliament one is left with the impression that each side believes they are smarter and better than the other. I am not so sure. 

Perhaps this is all my imagination. Beliefs do not clump and it only appears this way because of the tendency of individuals to purport to speak for groups even though many members don’t agree with the speaker’s point of view.

I find beliefs and how we come to them to be an interesting puzzle. How can two thoughtful, logical, clever individuals presented with the same set of facts come to such different conclusions? And, why do these conclusions clump together? 

Incidentally, I assume that there has been lots of thought and research done in this area. Time to do some reading...