Aligned heart rates indicate real-world social connection and engagement

When people are close-both physically and emotionally-their heart rates begin to align, rising and falling together. Could such cardiac alignment be used as a way to measure social engagement and connection in everyday settings? Hanlu He and colleagues used data collected by 72 students visiting New York City as part of an audio engineering competition.

The students collected data with hearing aids that recorded ambient noise, Garmin wristbands that measured heart rate, and mobile phones that recorded GPS data. Participants were classified as physically close when they were within 20 meters of one another. Participants' heart rate synchrony was stronger when they were together, especially during close-proximity interactions and joint attention to shared stimuli, such as attending the same lecture.

People who were socially familiar with one another before the trip had significantly higher levels of synchrony. Complex interaction environments with challenging listening conditions were associated with reduced heart rate synchrony, suggesting that listening conditions might influence the degree of physiological alignment. Noise and difficulty hearing target sounds could cause stress or increase the demand for auditory perception and compensation, reducing cognitive resources for interpersonal dynamics. Alternatively, conversation or the shared attention to an auditory stimulus could be part of what drives heart rate synchrony.

According to the authors, interpersonal physiological synchrony emerges in naturalistic social settings and can be used as a reliable marker of real-world social engagement.