The myth that when women live together their menstrual cycles become synchronised has long persisted – despite research showing there’s no evidence that this so-called McClintock effect exists. Any overlap that does happen is probably just down to chance.

However, just because this isn’t true doesn’t mean our bodies don’t sync with those around us in other ways. In fact, more and more scientific evidence of this happening is being discovered.

There are two key ways our bodies can “sync up” with people we’re close to. The first is synchronisation, where physiological or behavioural processes show coordinated patterns. The second is co-regulation, where the emotional or physiological state of one person influences another.

Our hearts have a remarkable ability to synchronise when we do things together.

For instance, a small study of 27 couples showed co-regulation of both heart rate and heart rate variability – a metric that represents the time between heartbeats. These metrics have also been shown to be synchronised when couples sleep in the same bed.

But it isn’t just couples this happens to. Research has found that choral singers also exhibit synchronised fluctuations in their heart rate when they sing together. Their heart rate increases and decreases at the same time as they breath in and out. This is caused by their breathing........

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