Writing "Dear Sir/Madam" at the top of a letter is sexist hangover from past centuries when men were considered superior to women, psychologists have claimed.
By continuing to refer to couples with the man's name first – "David and Sarah" rather than "Sarah and David" – people are unwittingly reinforcing gender stereotypes that emerged in the 16th Century, according to researchers.
From William Shakespeare's Romeo & Juliet and the nursery rhyme Jack and Jill to accepted terms of address like "Mr and Mrs", written English is rife with psychological sexism, it is claimed.
Academics at the University of Surrey conducted a series of tests to investigate the persistence of the male-first name convention.
They found that Google searches for common English name pairings produced significantly more results when the man's name was written first – 79pc compared to 21pc for female-first combinations.
In a separate experiment, 121 volunteers who were asked to write down possible names for an imaginary "traditional couple" were significantly more likely to put the man first. No such trend was witnessed when people where asked to name "non-conventional" couples.
Sexist stereotypes even influence how we describe homosexuals. When asked to list the personal and physical characteristics of an imagined same-sex couple, people were more likely to assign masculine traits to the person they had named first.
Dr Peter Hegarty, who led the study, said: "The results of our studies suggest that people tend to put men, or male qualities, before women. As this is a remnant of the sexist grammar of the 16th century, it would seem that psychologically we are still sexist in writing."
In the paper published in the British Journal of Social Psychology, he wrote: "Many centuries ago, English language specialists were prescribed to name men before women so that everyone's language use would reflect a patriarchal order which was said to be natural and proper."
He added: "In a modern culture where such beliefs are seen as antiquated and wrong, the sexism that persists is likely to be subtle and unacknowledged in form."
Before the 16th Century there were no set rules for which half of a couple should be named first, although letters tended to be addressed to the man of the household.
Academics have proposed other explanations for the persistent popularity of male-first name pairings.
Some have argued that it makes linguistic sense for men's names to come first as they tend to be shorter and contain harder consonants. The most popular men's names are also more common than the most popular women's names, giving them a familiarity that could lead to their being given priority.
But the University of Surrey researchers said that their experiments showed that outdated sexism was the only sufficient explanation.
They pointed to other instances in which men are given precedence over women. In cultures that read left to right it is still more common for men to be placed to the left of women in photos, while scientific papers that compare data on the sexes tend to present the information on men first.