If you feel like your spouse does not understand you, it may be because you are too close to them, claims new research.
Psychologists believe that when two people know each other too well they assume too much shared knowledge and their language becomes dangerously ambiguous.
This "closeness communication bias" can lead to long term misunderstandings, rows and even relationship problems, they believe.
The research by University of Chicago and Williams College in Massachusetts found that often couples and good friends communicate with each other no better than they do with strangers.
Sometimes they are clearer with strangers because they assume no common knowledge.
But in contrast to Oscar Wilde's remark that "the proper basis for a marriage is mutual misunderstanding", the phenomenon could cause problems.
"People commonly believe that they communicate better with close friends than with strangers," said Prof Boaz Keysar, co-author.
"That closeness can lead people to overestimate how well they communicate. Your language can become so ambiguous. The brain becomes lazy.
"But it can backfire and the misunderstanding can lead to rows in the future."
Prof Keysar, who said he carried out the work to demonstrate to his wife that some things she thinks are clear are not always clear, and the team tested the theory on 24 married couples.
The spouses sat in chairs with their backs to each other and tried to discern the meaning of each other's ambiguous phrases.
The researchers used phrases common in everyday conversations to see if the spouses were better at understanding phrases from their partners than from people they did not know.
The spouses consistently overestimated their ability to communicate, and did so more with their partners than with strangers.
Prof Keysar's colleague Prof Kenneth Savitsky said: "A wife who says to her husband, 'it's getting hot in here,' as a hint for her husband to turn up the air conditioning a notch, may be surprised when he interprets her statement as a coy, amorous advance instead.
"Some couples may indeed be on the same wavelength, but maybe not as much as they think. You get rushed and preoccupied, and you stop taking the perspective of the other person, precisely because the two of you are so close."
A similar experiment with 60 Williams College students showed that the phenomenon also applies to close friends too.
"Our problem in communicating with friends and spouses is that we have an illusion of insight. Getting close to someone appears to create the illusion of understanding more than actual understanding," said co-author Prof Nicholas Epley.
Prof Savitsky said it was always important to bear in mind the point of view of others – no matter how close to them you are.
The research is published in the journal of Experimental Social Psychology.