London, Oct 5 (IANS) Couples deeply in love speak and write alike, mimicking words and phrases that each other uses, reflecting the state of their relationship.

But if it goes bad then the common language breaks down and they begin to sound more like strangers again.

Researchers in the US made the discovery after studying the poetry and letters of two famously passionate marriages - the Victorian poets Elizabeth Barrett and Robert Browning and their 20th century equivalents Ted Hughes and Sylvia Plath.

They found that in both their work and their private letters the couples used "language style matching" that became most intense as their relationships became most intense, reports the Telegraph.

In the case of Hughes and Plath - whose relationship was far more volatile - it dramatically peaked and then troughed as their marriage fell apart.

The study suggests 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, according to the Journal of Personality and Social Psychology.

"When two people start a conversation, they usually begin talking alike within a matter of seconds," said Professor James Pennebaker, a psychologist from the University of Texas, who co-authored the study.

He and his co-author Molly Ireland said that computer analysis of the number of language style matches is an objective way of testing the current state of someone's relationship.

"Because style matching is automatic it serves as an unobtrusive window into people's close relationships with others," said Ireland.

The researchers used computer analysis to calculate the style-matching scores for both pairs of poets.

It showed that the number of linguistic matches hit their height in the middle of their relationship - 1,200 for the Brownings and 2,789 for Hughes and Plath.

It then dropped off to less than half towards the end of both relationships.