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Why Couples Often Start to Look and Sound Alike

An intimate relationship is a powerful force, in which two morph into one.

Key points

  • As close friends and relatives interact, their heart rates sync up.
  • Positive emotions are felt in physical ways, as heart rates calm and oxytocin increases.
  • In long-term marriages, spouses begin to resemble each other physically and physiologically.
WAYHOME studio/Shutterstock
Source: WAYHOME studio/Shutterstock

Connection isn’t just a metaphor. When people share emotions and space, they start to bond and alter each other. They literally become different. This was demonstrated in the unusual arena of fire-walking. Every June in Spain, thousands gather in the village of San Pedro Manrique to watch brave individuals walk barefoot over smoldering oak embers in front of cheering crowds. One year, researchers strapped heart monitors on some of the fire walkers and spectators. As volunteers stepped onto the glowing coals, their heart rates synchronized with the heart rates of their family and friends watching. Strangers, however, did not synchronize with the fire walkers.

Invisible chemical processes were connecting those who cared about each other. In other settings, lovers whose hearts beat together feel closer and more stable, and clients whose hearts synch with their therapists’ hearts report better sessions. Scholars have also found that tense emotions are jarring to the heart rate. One wrote: “During the experience of negative emotions such as anger, frustration, or anxiety, heart rhythms become more erratic and disordered, indicating less synchronization ... between the parasympathetic and sympathetic branches of the autonomic nervous system (ANS).” In other words, out-of-sync emotions produce out-of-sync heart rates. The heart isn’t just a metaphor for love, it is part of it. Another study found that high-conflict couples tend to have thicker carotid arteries, which suggests being hard-hearted is bad for marriage and health.

However, positive emotions from one partner can act as a healing force. When one simply projects a caring or concerned feeling toward another, it results in measurable changes to the recipient’s heart. Good feelings are palpable and spread from people who are connected. Another study at a wedding found the oxytocin levels of the bride, groom, close relatives, and friends all surged together.

Love connects and changes partners. Have you ever laughed about how old married couples look alike? Science backs this up. Robert Zajonc showed volunteers pictures of couples, some in their first year of marriage, and some in their 25th. The researchers removed extra information in the photos to leave only faces. Volunteers were able to pick the long-term spouses more often than unconnected people or short-term spouses. People’s faces did grow more similar over time, and the researchers speculated that one of the reasons was that lovers look at each other and empathize together for years, mimicking and reflecting what they see. Long-term couples also have unusually similar kidney functions, cholesterol levels, and grip strength.

An intimate relationship isn’t just a social agreement; it is a life-altering bargain in which two people become one, in looks, actions, and identity. Such is the power of love.

Adapted from Love Me True: Overcoming the Surprising Ways We Deceive In Relationships.

Facebook image: WAYHOME studio/Shutterstock


Ivana Konvalinka, Dimitris Xygalatas, Joseph Bulbulia, Uffe Schjødt, Else-Marie Jegindø, Sebastian Wallot, Guy Van Orden, and Andreas Roepstorff, "Synchronized Arousal Between Performers and Related Spectators In A Fire-Walking Ritual." Proceedings of the National Academy of Sciences 108, no. 20 (2011): 8514-8519.

Rollin McCraty, Mike Atkinson, Dana Tomasino, and Raymond Trevor Bradley, "The Coherent Heart: Heart-Brain Interactions, Psychophysiological Coherence, And The Emergence Of System-Wide Order." Integral Review 5, no. 2 (2009): 10-115.

Steven P. Reidbord, and Dana J. Redington, "Nonlinear Analysis of Autonomic Responses in a Therapist During Psychotherapy," The Journal of Nervous and Mental Disease 181, no. 7 (1993): 428-435.

Robert B. Zajonc, Pamela K. Adelmann, Sheila T. Murphy, and Paula M. Niedenthal, "Convergence in the Physical Appearance of Spouses." Motivation and Emotion 11, no. 4 (1987): 335-346.

Drake Baer. Being Married for Decades Means That Your Bodies Become Biologically Alike. Science of Us, May 26, 2016.