The simplest touch from a romantic partner can mean something totally different during a tough dinner with the in-laws versus an afternoon stroll together. Turns out, it’s not just context.

In this study, researchers compared how effectively romantic couples and strangers communicate emotions with touch. Participants sat at opposite sides of a table, separated by a black curtain. The “touchers” were asked to express a particular emotion with one of four gestures—squeeze, shake, stroke or pat. The people being touched then chose one of 12 emotions they thought was conveyed.

Results favored the couples: Both strangers and couples effectively communicated universal emotions (anger, disgust and fear) and prosocial emotions (gratitude, love and sympathy), but only couples understood more subtle, self-focused emotions (embarrassment, envy and pride). Looks like couples really do have a private language!