You know you’ve been with your spouse a long time when you feel as if you have developed a sixth sense for his emotions—you can just feel when he is upset. It turns out you may actually be smelling his state of mind, according to a study reported this past June in the journal Social Neuroscience.

The researchers tested the ability of par­ticipants to identify, via body odor, their partner’s or a stranger’s chemosensory emotional cues—chemical compounds released by the body that have no noticeable odor but nonetheless transmit information about emotional states. First, the team placed pads in the armpits of “sweat donors” to capture their body odor as they watched videos intended to induce happiness, fear or sexual arousal, as well as when they were in a neutral mood. (Self-reported mood ratings were confirmed by measures of heart rate and skin conductance.) Next, they had partners smell the sweat samples to determine whether they could differentiate between emotional and neutral chemosensory cues.  Although their ability to distinguish emotional sweat from neutral sweat was significantly above chance for both partners and strangers, their detection was more accurate for partners’ samples and even more so the longer the couples had been together.

Participants were not able to identify the specific emotions represented by each sample because chemosensory emotional cues operate mostly at a subconscious level, unlike signals from facial expressions, voice or touch. The results, however, confirm what long-term couples have discovered time after time—communication happens on a surprising number of levels.