The theory that opposites attract is a myth, scientists have said, after finding that people are only attracted to those who hold the same views and values as themselves.
In a finding hailed as a "paradigm shift" for the understanding of relationships, researchers found like-minded people will be drawn together but keep their distance from those who do not adhere to their beliefs.
It suggests strangers hoping to hit it off would do better to play to their similarities rather than trying to impress the other person with attributes which make them unique.
"Picture two strangers striking up a conversation on a plane, or a couple on a blind date," said Angela Bahns, professor of psychology at Wellesly College, Massachusetts.
"From the very first moments of awkward banter, how similar the two people are is immediately and powerfully playing a role in future interactions.
We're arguing that selecting similar others as relationship partners is so common that it could be described as a psychological default."
The researchers, from Wellesly and the University of Kansas, asked more than 1500 pairs, including couples, friends and acquaintances, to complete a survey about their values, prejudices, attitudes and personality traits.
The information was then compared to see how similar or different each pair was and to see whether people in longer relationships had more in common. It emerged that all pairings held similar life views even if they had only just met. In a second experiment, the researchers surveyed pairs who had just met in college, and then spoke to the same pairs later. There was virtually no change in beliefs over time, suggesting those who go into a relationship hoping to change the opinions of the other are unlikely to succeed.
"Change is difficult and unlikely; it's easier to select people who are compatible with your needs and goals from the beginning," Prof Bahns said.
The research was published in the Journal of Personality and Social Psychology.