"When two people start a conversation, they usually begin talking alike within a matter of seconds," says James Pennebaker, psychology professor and co-author of the study. "This also happens when people read a book or watch a movie. As soon as the credits roll, they find themselves talking like the author or the central characters."

This tendency is called language style matching or LSM. It is the focus of Pennebaker's and co-author Molly E. Ireland's study published in the September issue of Journal of Personality and Social Psychology.

"Because style matching is automatic," says Ireland, a psychology graduate student, "it serves as an unobtrusive window into people's close relationships with others."

Ireland and Pennebaker tracked the language used by almost 2,000 college students as they responded to class assignments written in very different language styles. 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."

The researchers extended their work by analyzing the written language of famous authors. For example, Sigmund Freud and Carl Jung wrote to each other almost weekly over a seven-year period as their careers were developing. Using style-matching statistics, Ireland and Pennebaker were able to chart the two men's tempestuous relationship from their early days of joint admiration to their final days of mutual contempt by counting the ways they used pronouns, prepositions and other words, such as the, you, a and as, that have little meaning outside the context of the sentence.

The style-matching approach proved to be a powerful bellwether of marriages as well. Style-matching scores were calculated between poetry written by two pairs of spouses, Victorian poets Elizabeth Barrett and Robert Browning and 20th century poets Sylvia Plath and Ted Hughes, which mapped major changes in their relationships.

"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.

Differences in style matching between the two couples were revealing as well. Even at the high point of their marriage, Hughes and Plath were less in sync than the historically more harmonious Brownings were at their lowest point.

Ireland and Pennebaker are investigating whether LSM during everyday conversation can be used to predict the beginning and end of romantic relationships. Style matching has the potential to quickly and easily reveal whether any given pair of people -- ranging from business rivals to romantic partners -- are psychologically on the same page and what this means for their future together.

Note: If no author is given, the source is cited instead.

• Language Acquisition
• Social Psychology
• Relationships
• Child Development
• Psychology
• Borderline Personality Disorder

• Ego psychology
• Neurosis
• Self-concept
• Developmental psychology
• Psychotherapy
• Anchoring bias in decision-making