When it comes to love, there are no hard and fast rules though many people follow the age-old theory that opposites attract.
But now a study has found that more often that not, similarity rules the day.
Researchers at Berkeley found that people are drawn to potential romantic partners if they are of their own or similar league and desirability, which they called the 'matching hypothesis'.
Of course personality traits and common interests play a factor but for that instant attraction, like is drawn towards like, putting paid to the phrase, 'You're out of my league'.
For their research, the authors of the study turned - as most singletons do today - to online dating sites.
They measured the popularity of more than 3,000 heterosexual users of a site and looked at the popularity of each.
Popularity was defined by the number of opposite-sex individuals who had sent unsolicited messages to a user.
Analyses indicated that high-popularity users contacted other popular users at a rate greater than would be expected by chance.
Similarly, the less popular users of the site also contacted other low-popularity users.
The researchers then conducted a follow-up study of more than a million users and found a similar result - when it comes to dating, potential mates stick to someone in their own league.
The authors found that: 'Individuals on the dating market will assess their own self-worth and select partners whose social desirability approximately equals their own.
'Using data collected in the laboratory and from users of a popular online dating site, the authors found evidence for matching based on self-worth, physical attractiveness, and popularity, but to different degrees and not always at the same stage of the dating process.
'The most striking prediction is that undesirable individuals will choose undesirable partners.'