When comparing how happy and unhappy partners communicate, it has been found that

happy and unhappy partners make the same sorts of statements, but they are interpreted more negatively by unhappy partners than they are by happy partners.

it is easier to predict the behavior of one person from that person's partner's behavior in an unhappy couple than in a happy couple.

happy couples tend to disagree about fewer topics than unhappy couples do$.$

partners in happy couples have a more accurate perception of the motivations behind each other's behaviors than partners in unhappy couples do$.$