If you want to find out whether your relationship will last pay very close attention to how your partner speaks.
A study has found that perfectly matched couples mimic each other's language during conversations.
The more your other half copies your slang and speech patterns, the more psychologically connected you are.
According to American researchers, couples are most likely to perform this 'language style matching', or LSM, during happier phases of their relationship.
"Because style matching is automatic, it serves as an unobtrusive window into people's close relationships with others," the Daily Mail quoted Molly Ireland, who helped lead the study, as saying.
Researchers started off tracking the language used by almost 2,000 university 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 in a similarly complex, serious style.
But if it was posed in a casual, familiar manner, the students punctuated their answers with slang and terms such as 'like' and 'kinda'.
James Pennebaker, psychology professor and co-author of the study, said: "When two people start a conversation, they usually begin talking alike within a matter of seconds."
To see how this applied to close personal relationships, the researchers then analysed the correspondence of famous writers - such as Sigmund Freud and Carl Jung, who wrote to each other almost weekly over a seven-year period as their careers were developing.
By analysing the LSM in their letters, the researchers were able to chart the two men's tempestuous relationship - from their early days of joint admiration to their final days of mutual contempt.
They compared their language styles 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 researchers then extended the study to romantic relationships by assessing the LSM of two famous couples - Victorian poets Elizabeth Barrett and Robert Browning, and 20th century poets Sylvia Plath and Ted Hughes.
The report revealed that major changes in each couple's marriage were mapped out in the poetry.
Ireland said: "Style words in the spouses' poems were more similar during happier periods of their relationships, and less synchronised toward each relationship's end."
The varying levels of LSM between the two couples were also revealing - as even at the happiest stage of their marriage, Plath and Hughes were less in sync than the historically more harmonious Brownings were at their lowest point.
The researchers are now investigating whether LSM during everyday conversation can be used to predict the beginning and the end of romantic relationships.
The study has been published in the Journal of Personality and Social Psychology.