What if the key to a strong, happy relationship wasn’t just communication or shared values—but something as simple as a smile? New research suggests that the way couples synchronise their smiles could be a powerful indicator of relationship satisfaction.
A recent study published in Emotion revealed that couples who experience greater relationship happiness tend to have better smile synchrony—that is, they smile together more often and in a more coordinated way. In contrast, couples seeking therapy for relationship distress showed significantly lower levels of smile alignment.
The power of emotional synchrony
We all know that emotions play a huge role in our relationships and when partners feel emotionally in tune with one another, it creates a sense of closeness and understanding. This phenomenon, known as emotional synchrony, happens when two people naturally align their feelings and behaviours—whether through shared physiological states, verbal cues or nonverbal gestures.

While past studies have looked at synchrony in speech patterns or even heart rates, this new research focuses on something simpler and more universally recognised: smiling. Smiles are powerful nonverbal cues that convey warmth, happiness and connection and the new study suggested that how well partners mirror each other’s smiles could be a subconscious signal of how connected they feel.
Smiling in sync: The study behind the science
Researchers at Ben-Gurion University of the Negev recruited 61 cohabiting couples—30 of whom reported high relationship satisfaction and 31 who were attending therapy for relationship distress. The couples participated in a series of recorded conversations about both positive (relationship strengths) and negative (areas of disagreement) topics.
Their facial expressions were analyzed using advanced facial recognition software, which tracked how often and how quickly they smiled in response to each other. It was found that happy couples smiled together more often and responded to each other’s smiles more quickly where their smile synchrony score averaged 0.46 (on a scale from 0 to 1), while therapy-seeking couples averaged just 0.32.
When one partner smiled, the other responded in about 0.62 seconds in happy couples—whereas distressed couples took nearly twice as long.
What does this mean for your relationship?
Before you start timing your partner’s smile responses, take a deep breath! The researchers aren’t suggesting that couples should force themselves to smile more.

Instead, the study highlights how naturally occurring, unconscious behaviours—like mirroring a partner’s happiness—can reflect a relationship’s emotional health. Interestingly, smile synchrony was more pronounced during positive discussions than negative ones but even in difficult conversations, happier couples still showed better alignment in their smiles, suggesting that shared emotional expressions help build resilience in relationships.
Can you improve your smile synchrony?
While smile synchrony happens naturally, it is possible to nurture emotional connection in a relationship. Here are a few simple ways to encourage it –
- Be Present: Engaging in deep, meaningful conversations with your partner can help you tune into each other’s emotional cues.
- Make Eye Contact: Looking into your partner’s eyes can naturally lead to more shared smiles and a greater sense of connection.
- Share Positive Moments: Whether it’s reminiscing about a happy memory or laughing over an inside joke, creating joyful experiences together can encourage natural smile synchrony.
- Practice Active Listening: Show genuine interest in your partner’s words and emotions, which can naturally lead to more reciprocal expressions of warmth.
The bigger picture: Smiling as a relationship indicator
While smiling together isn’t a magic fix for every relationship challenge, it offers an interesting glimpse into how couples interact emotionally. Just as a lack of laughter can signal deeper disconnection, a shared smile can be a small but meaningful sign of emotional attunement.
As lead researcher Reut Machluf-Ruttner put it, “Despite being automatic and largely uncontrollable, these signals are highly indicative and can serve as markers of relationship quality.”
So, the next time you catch yourself smiling at your partner, pay attention because that simple act might be saying more about your relationship than words ever could.