Can Romance Be Reduced to Pronouns?

Behavioral scientists have long known that humans, whether in the schoolyard or in a dimly lighted bar, have a tendency to subconsciously mimic the sounds, style and movement of others. Recent research, however, shows that this mimicry also extends to how we speak and write. Even the least important words we choose can say a lot about us.

In one unusual experiment, 187 men and women gathered on the Northwestern University campus to take part in several four-minute speed dates. The couples talked about their respective majors and where they grew up, but none of that interested the University of Texas at Austin psychologist James W. Pennebaker. Instead, his focus was on the barely noticed personal pronouns (I, you, me), articles (the, a), prepositions (for, of, on), conjunctions (but, and) and other small words. These commonly used so-called function words, about 180 in all, Pennebaker says, are processed rapidly and subconsciously. And our use of them can reveal, among other things, whether a romance will work out or how well two people work together.

In the speed-dating study, Pennebaker and his colleague Molly Ireland found that couples who used similar levels of personal pronouns, prepositions and even articles were three times as likely to want to date each other compared with those whose language styles didn’t match.() The metric, called language style matching (L.S.M.), was also better at predicting who didn’t make a love connection than the individuals themselves, several of whom showed interest in a partner who did not reciprocate.() “It does better than humans themselves who are in the interaction,” said Pennebaker, author of the new book “The Secret Life of Pronouns.” “Some of the most revealing words we use are the shortest and most forgettable.”

The metric has other applications. An analysis of instant-message exchanges between dating couples used L.S.M. to correctly predict who would be together after three months and who wouldn’t.() More recently, researchers also found that groups with the highest levels of language mimicry performed the best on various tasks. Pennebaker’s team even analyzed the letters and writing of famous couples, including the poets Sylvia Plath and Ted Hughes. In the final, tumultuous years of their marriage, their already-different writing styles became even less synchronized.

Synchrony, however, does not always mean that two people like each other. Analyses of arguments, like the volatile exchange several years ago between the talk-show hosts Rosie O’Donnell and Elisabeth Hasselbeck, showed that the women used astonishingly similar speech patterns when they were arguing.() To let people see for themselves, Pennebaker offers an online diagnostic in which individuals can copy and paste their own I.M. conversations. I did this with an argument I was having with a friend, and we had 88 percent L.S.M. — daytime talk show territory.() But given the volume of e-mail, texts and Facebook posts we write, synchrony opens a new frontier into our most personal thoughts. Even the 140 character variety.