The character trait of openness to new ideas and experience is a consequence of a lack of moral foundations.
If moral foundations really do result from natural selection then it is likely they allow us to see and react to real world threats to our individual and collective survival. One who employs only half the foundations sees only half the threats. It’s only natural that such a person will be “open” to every new idea that comes along. The phrase “Openness to new ideas” is a misnomer; it’s a politically correct spin that makes lemonade out of the lemons of threat blindness and moral groundlessness. It is the manifestation of Sandel’s unencumbered self.
The lack of moral foundations also explains cognitive complexity. With fewer foundations the elephant has no particular reason to prefer one path over another, and so every potential choice becomes an exercise in objective analysis of pros and cons, costs and benefits.
Some have suggested that openness to new ideas might be a moral foundation. I disagree, and strongly. It’s a character trait that results from a partial application of the moral foundations that have already been described.
Moral foundations come in pairs. What would be the opposite of openness? Some have suggested that it would be closed mindedness. This is a misperception of the trait. Its opposite would be threat sensitivity, which more naturally results from the employment of a greater number of moral foundations.
[UPDATE, 12/29/15: As of July 8, 2012 Dr. Haidt agreed with my assessment that Openness is not a moral foundation and that the opposite of Openness is threat sensitivity, but disagreed with my idea that it’s connected with moral foundations. He explains this in a comment, below]