From He That Hath Not

...simply putting someone into a weak social position impairs his cognitive function. Conversely, “empowering” him, in the dread jargon of sociology, sharpens up his mind.

Dr Smith focused on those cognitive processes that help people maintain and pursue their goals in difficult and distracting situations. She suspected that a lack of social power may reduce someone's ability to keep track of information and make plans to achieve his goals.

http://www.economist.com/science/displaystory.cfm?story_id=11402754

I feel that I have had personal experiences that tally with this finding.

It also tallies with an assertion in The Lucifer Principle.