Most couples instinctively recognize the power of a shared smile, but researchers have now uncovered its deeper significance in maintaining healthy relationships.
Smiles between romantic partners not only reflect mutual affection but also synchronize in ways that differentiate satisfied couples from those experiencing distress.
A recent study by Reut Machluf-Ruttner and colleagues, published in the journal Emotion (2025), reveals that nondistressed couples exhibit significantly higher levels of smile synchrony.
Nondistressed couples spontaneously mirror each other’s smiles more often and more quickly than those seeking therapy for relationship distress.
These findings suggest that the coordination of smiles could serve as a subtle yet powerful indicator of relationship health.
The quality of romantic relationships is widely recognized as crucial for both psychological and physical well-being.
Previous research has consistently linked higher marital satisfaction with better mental health, reduced stress, and even improved physical health outcomes.
Conversely, relationship distress has been strongly associated with increased risks of depression and emotional difficulties.
The current study, conducted at Ben Gurion University of the Negev in Israel, involved 61 couples—30 nondistressed and 31 distressed, therapy-seeking pairs.
Each couple participated in a laboratory session where they discussed both positive and negative aspects of their relationship during four six-minute conversations.
Advanced facial expression analysis software continuously tracked the participants’ smiles, enabling precise measurements of smile synchrony.
Results demonstrated clear differences: nondistressed couples not only mirrored each other’s smiles more frequently but also did so more quickly compared to distressed couples.
Specifically, the nondistressed couples showed higher overall smile synchrony, occurring within shorter intervals of around 0.6 seconds.
In contrast, distressed couples took significantly longer—approximately one second—to achieve their peak synchrony.
Why might the timing of synchronized smiles matter?
Researchers suggest that quicker reciprocation of smiles indicates better emotional responsiveness, mutual understanding, and connection between partners.
Essentially, couples who rapidly mirror each other’s smiles are likely more attuned emotionally, fostering deeper bonds and enhanced relationship satisfaction.
Interestingly, this effect was strongest when couples discussed positive aspects of their relationship.
During these conversations, smile synchrony increased, reinforcing the notion that shared positive emotions play a crucial role in fostering closeness.
This aligns with previous studies highlighting how shared laughter and positive emotional exchanges enhance relationship quality.
These findings have meaningful implications for couples therapy and relationship counseling.
Smile synchrony, as a nonverbal indicator, could potentially serve as an objective measure to assess relationship health and monitor therapeutic progress.
It might also assist therapists in identifying couples at risk, enabling earlier interventions.
However, the study acknowledges certain limitations.
Participants were primarily younger couples in the nondistressed group, compared to the typically older, distressed couples who had longer relationship durations and more life stressors such as parenting.
While age differences and life circumstances were statistically controlled, future research might explore these factors further to better understand their influence on emotional synchrony.
Moreover, future studies could expand upon these findings by investigating smile synchrony across diverse contexts and relationship dynamics, including interactions outside the laboratory setting.
Understanding the nuances of this phenomenon might help clarify its potential role as both a diagnostic and therapeutic tool.
Citation
Machluf-Ruttner, R., Sbarra, D. A., Shahar, B., Sofer, C., & Bar-Kalifa, E. (2025). The dance of smiles: Comparing smile synchrony in nondistressed and therapy-seeking couples. Emotion, 25(4), 841–852. https://doi.org/10.1037/emo0001466
