It is now possible to predict the success of a relationship, according to scientists.
Researchers have discovered, in a new study, how to tell whether a couple will stay together or split up.
Psychologists claim behaviour during the early days of dating can reveal how the union will progress.
They found those who had similar needs, but different interests, tended to be together for longer.
Canadian and German researchers regularly interviewed 2,000 couples over a seven-year period.
They discovered intimate relationship behaviour patterns could signal whether a partnership was thriving or failing.
The team determined satisfaction by asking couples to what extent they considered their needs were being met.
In general, those who had similar needs, a need for closeness for example, but who also wanted to continue pursuing their own interests, usually stayed together longest.
Couples could therefore have advance information on the probability of their staying together.
Study author Dr Christine Finn, from the University of Jena in Germany, said: “Predictions as to the longevity of a relationship are definitely possible.
“Right at the outset of a relationship, one can find typical features - that is to say certain prediction variables - that provide information on whether or not the relationship will be long-lasting.”
Dr Finn said there are two psychological models which describe the course of a relationship.
One states that all couples are initially more or less equally happy, and if the relationship ends in separation, this can be traced back to problems that developed over the course of the couple’s time together.
The second assumes the two people start at different levels of happiness - they generally maintain these levels, but a more negative initial situation increases the likelihood of failure.
Dr Finn said: “We too can confirm there are differing levels to begin with. In addition, happiness declines in both groups.
“However, in those who later separate, this happens significantly faster, meaning that a person who starts off unhappy becomes increasingly unhappy.”
But Dr Finn does not want to be pessimistic.
She said: “Even if couples split up after a time, it can still be a valuable and important phase in their lives, which might have a positive influence on the next relationship.
“Couples can also consciously influence and work on their mutual interests and on cultivating closeness as well as independence - no relationship is doomed to fail from the outset.”
She believes the results could be valuable to counselling centres and therapists.