From here
http://news.yahoo.com/s/livescience/20090701/sc_livescience/peopleunsureofbeliefsaremorecloseminded

People who are less confident in their beliefs are more reluctant than others to seek out opposing perspectives, researchers said today.
The findings, which are based on a review of more than 90 studies, shed light on the debate over whether people intentionally steer clear of views conflicting with their own, or whether they are just exposed more often to ideas that conform to their own.
The former seems to be the case. Another recent study revealed that college students gravitated toward news that fit their views.
While it's not news that like-minded people often flock together, the new review suggests we actively keep our blinders on when opposing views are nearby. The review is detailed this month in the journal Psychological Bulletin.
Some more so than others ,
Overall, the studies suggested people are about twice as likely to cherry-pick information that supports their own viewpoints than to consider an opposing idea. Nearly 70 percent cherry-picked compared to about 30 percent who ponder the other side.
Close-minded individuals opted for information that went along with their views 75 percent of the time.
"Close-minded people are very certain and dogmatic in their views, and generally believe that there is a single correct point of view," said study researcher Dolores Albarracin, a psychology professor at the University of Illinois at Urbana-Champaign. "The implication is that you have a group of people who would only seek to confirm their points of view, resisting all evidence to the contrary via avoidance of exposure."
And since even a slight breeze could flatten a house of cards, the researchers found people with little confidence in their own beliefs are less likely to expose themselves to contrary views compared with their confident counterparts.