""When two people start a conversation, they usually begin talking alike within a matter of seconds," says James Pennebaker. ...
If the essay question was asked in a dry, confusing way, the students answered accordingly. If asked in a flighty, "Valley girl" way, the students punctuated their answers with "like," "sorta" and "kinda."...
"Style words in the spouses' poems were more similar during happier periods of their relationships and less synchronized toward each relationship's end," Ireland says."
Unfortunately, the paper isn't online, but you can see the abstract: http://www.ncbi.nlm.nih.gov/pubmed/20804263