"Familiarity with a partner enhances detection of emotional cues in that person's smell," Rice University psychologist Denise Chen told a science weekly.
To reach the conclusion, Chen and her team looked at 20 heterosexual couples who had been living together for between one and seven years.
As volunteers viewed videos meant to induce self-reported feelings of happiness, fear and sexual arousal, underarm pads collected their sweat.
Then the participants smelled odors from four jars that held the sweat from their partner or a stranger of the opposite sex, and tried to name one smell that came from a person who was experiencing a particular feeling.
One jar held sweat that was collected during a video meant to induce particular emotions. The other jars contained perspiration that had been collected during a neutral video, reports a major newspaper.
Nearly two-thirds of the time, participants could pick up the specific emotions from their partner's body odor, and couples who'd lived together the longest were best at homing in on each other's emotional odors, the study found.
The accuracy rate dropped to 50 percent for opposite-sex strangers. There was little difference in the couples'' ability to identify odors linked to fear, happiness or sexual arousal.
The study was presented at the Association for Psychological Science annual convention.