Mental Exercise?

In this post a blogger draws attention to this paper on the phenomenon that college educated people tend to live longer.  This seems to hold even after taking into account other factors like income and lifestyle choices such as smoking.  One thing that wasn't mentioned was the possibility that mental exercise has beneficial health effects.

Indeed it would be considered quite an oversight if a researcher had neglected physical exercise as a health factor, and yet to overlook mental exercise is considered much less serious.  Since the brain is responsible for using up a large proportion of the calories that we consume, it is difficult to see why this is the case.