When people feel emotionally close, their bodies may start to act in tandem. A new study published in Biological Psychology offers evidence that this alignment can reach the level of the heart. Researchers found that married couples from lower socioeconomic backgrounds were more likely to show synchronized heart rate patterns than couples from higher socioeconomic backgrounds. The findings suggest that social and economic conditions may shape not only how people relate to one another emotionally, but also how their bodies respond during social connection.
Previous research has shown that people from lower-income and lower-education backgrounds tend to emphasize relationships more than their more affluent peers. Studies suggest that individuals from these environments often rely more on their social networks for support, given that they face more external challenges such as financial strain and limited access to resources. This emphasis on social interdependence appears in how people think, feel, and behave. But until now, little was known about whether this tendency might also appear in physical processes, such as heart rate.
“Social connection is essential for human well-being and survival. And how we connect with others is shaped by the resources and opportunities we have. When socioeconomic resources are scarce, social relationships can become a refuge and a resource, taking on a particularly important role in people’s lives,” said Tabea Meier, a postdoctoral scholar affiliated with the University of Zurich, and Claudia Haase, an associate professor at Northwestern University, the corresponding authors of the study.
“Prior research has shown that people from less privileged backgrounds tend to be more interdependent and attuned to others, for example, in experiencing greater empathy and compassion. This stands in contrast to the individualism that tends to dominate more privileged social contexts.”
“However, much less is known about whether this attunement to others goes beyond experiences and behavior—whether it shows up in people’s bodies or physiology. Our study of married couples examined this question by probing how socioeconomic status relates to physiological linkage – the way spouses’ heart rates rise and fall together when they interact. In moments of deep connection, people’s hearts can beat in sync.”
For their study, the researchers recruited 48 married couples living in the Chicago area, resulting in a sample of 96 individuals. The couples varied widely in terms of income and education. Some earned less than $20,000 per year, while others made over $150,000. Their education levels also ranged from less than high school to advanced degrees. The sample included people from several racial and ethnic backgrounds.
Each couple participated in a three-hour lab session. After some initial procedures, they took part in two ten-minute conversations: one focused on a topic of conflict in their relationship, and another centered on a mutually enjoyable subject. During these conversations, the participants wore sensors that tracked their heart activity in real time. The researchers focused on a measure called “interbeat interval,” which is the amount of time between heartbeats. These second-by-second measurements allowed the team to assess how each spouse’s heart rate changed throughout the conversation.
The researchers analyzed how closely the spouses’ heart rate patterns mirrored each other. When both people’s heart rates sped up or slowed down together, this was called “in-phase linkage.” When one person’s heart rate increased while the other’s decreased, that was labeled “anti-phase linkage.” In both cases, stronger linkage meant a tighter correlation between spouses’ heart rate shifts. The team looked at how these two types of linkage were related to the couple’s socioeconomic background.
Across both conflict and pleasant conversations, couples from lower socioeconomic backgrounds showed higher in-phase linkage. In other words, their heart rates were more likely to change in the same direction. At the same time, they showed lower anti-phase linkage, meaning their heart rates were less likely to change in opposite directions.
This pattern suggests that less affluent couples tend to experience a stronger bodily connection during interpersonal interactions. Their heart rhythms moved more in unison, regardless of whether they were arguing or sharing positive memories. The difference was particularly strong for anti-phase linkage, which was much lower in lower-income and lower-education couples compared to their more privileged peers.
“When people connect, it’s not just their thoughts, feelings, and behaviors that can align – their bodies can, too,” Meier and Haase told PsyPost. “Our study found that couples’ socioeconomic backgrounds may shape how this connection unfolds at a physiological level. Specifically, the heart rates of spouses from less privileged backgrounds were more likely to change in the same direction (i.e., speeding up or slowing down together) and less likely to change in opposite directions (i.e., one speeding up while the other is slowing down) compared to those from more privileged backgrounds.”
These results held even after the researchers controlled for several other factors, including age and racial background. The effect was also more strongly tied to education than income, although both contributed to the findings.
Importantly, the level of synchrony did not appear to be linked to the emotional tone of the conversation or to how many times the couples used inclusive words like “we.” That suggests that the physiological linkage observed may be operating somewhat independently of what the spouses said or how they rated their emotions.
“These findings build on a long line of research showing that people from less privileged backgrounds tend prioritize relationships and are more attuned to those around them,” the researchers said. “Our study suggests, to our knowledge for the first time, that this connection may not only appear in feelings or behaviors, but also at a physiological level in the form of linked heart rates between spouses. It is a reminder that our social worlds live within us.”
There are a few caveats to consider. The sample size, although consistent with similar lab-based studies, was relatively small. It also focused on heterosexual married couples with children in the United States, which limits how broadly the results can be applied.
The study also did not look at how these heart rate patterns affect the couples over time. It remains unclear whether higher in-phase linkage leads to better relationship satisfaction, improved health, or other benefits. Some previous research suggests that synchrony may be helpful in many cases, but not always. For example, when couples are arguing, syncing up physiologically might sometimes make things worse by escalating conflict. On the other hand, moving in opposite directions might help one partner stay calm while the other is distressed.
“It is important not to oversimplify these results,” Meier and Haase explained. “Linked heart rates do not necessarily mean “better” or healthier relationships. Whether physiological linkage is beneficial or not may really depend on the context in which it occurs, for example, whether spouses are cracking up about an inside joke, are throwing harsh words at each other, or comforting each other in sadness. Future research can explore when and how different heart rate linkage patterns support or harm relationship satisfaction, well-being, and health.”
“Our study is a first step and there are many open questions that we would love the research community to pursue. While we worked hard to recruit a diverse sample of couples from all walks of life from the U.S. Chicagoland area, larger samples will be needed, ideally not just from the US. There are many other open questions. For instance, how does physiological linkage predict how satisfied spouses from less or more privileged backgrounds are with their relationship over time? And what are the consequences for mental and physical health? We look forward to more research in this area that connects the macro and the micro.”
“Socioeconomic status can shape our everyday lives in powerful ways, including how we connect with loved ones,” the researchers added. “Psychological research on couples has traditionally focused mostly on white, middle-class couples. Findings from our study, along with others, highlight the importance of inclusive approaches in the study of social connection. The couples in our study allowed us to gain a deeper understanding of how emotional dynamics and social connection may differ across socioeconomic contexts, and we are grateful that they shared their time and insights with us.”
The study, “Connected at heart? Socioeconomic status and physiological linkage during marital interactions,” was authored by Tabea Meier, Aaron M. Geller, Kuan-Hua Chen, and Claudia M. Haase.
