Here's the link: http://www.npr.org/blogs/health/2014/09/01/344043763/our-use-of-little-words-can-uh-reveal-hidden-interests

Relevant excerpt:

Pennebaker has counted words to better understand lots of things. He's looked at lying, at leadership, at who will recover from trauma.

But some of his most interesting work has to do with power dynamics. He says that by analyzing language you can easily tell who among two people has power in a relationship, and their relative social status.

"It's amazingly simple," Pennebaker says, "Listen to the relative use of the word "I."

What you find is completely different from what most people would think. The person with the higher status uses the word "I" less.