People who are narrow-minded and dogmatic have a poorer working memory capacity, which is what makes it harder for them to process new information. That's according to Adam Brown who tested 212 university students on a verbal working memory task.
The students listened to several sentences that had a word missing at the end, then after hearing all the sentences they had to propose words to fill in the gaps, in the right order.
They also completed a measure of dogmatism which gauged their agreement with statements like: “When it comes to differences in opinion in religion, we must be careful not to compromise with those who believe differently than the way we do.”
Brown found that the poorer a student's performance on the working memory task, the more likely they were to be dogmatic. Other measures such as their college admission exam performance (SAT), their age or gender didn't make any difference to this relationship.
“I predicted that it may be reasonable to expect differences in verbal working memory capacity, and this may directly affect one's ability to effectively process new information, especially if it is complex,” Brown said. “The results support this prediction.”
Brown, A.M. (2007). A cognitive approach to dogmatism: An investigation into the relationship of verbal working memory and dogmatism. Journal of Research in Personality, 41, 946-952.