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The science of heart rate variability synchronisation

THE SCIENCE (Examples)

Heart Rate Variability Synchronisation
Local Synchronisation

For several years it has been known that certain aspects of the physiology of two people who are in closely bonded relationship will tend to synchronise (Helm et al.,2012 and Palumbo et al., 2017 - research review) Some of the scientific research has studied the synchronisation of what is called heart-rate-variability (HRV) - the way our heart rates rise and fall with time. Heart rate changes for many different reasons such as when we exercise, become anxious or through the physiological demands from the organs of our body. It has also been shown that it can change by as much as 15 beats per minute due to positive emotional reactions, particularly during the experience of love or friendship. It is these changes that HeartBond records and analyses.

Both academic and our own research has shown that the HRV synchronisation effect is enhanced in pairs of people who are in a more bonded relationship. Our Heartbond app measures the strength of correlation in the changing hearts rates and turns this into a bonding score. The graph below shows how the heart rate variability of a married couple synchronised as they sat next to each other on a sofa and felt love for each other. The Heartbond app is designed to allow you to experience this amazing synchronisaton for yourself.

At present nobody is certain about what causes HRV synchronisation , although a number of hypotheses have been suggested. It might be that we can pick up subtle cues from our physical senses and unconsciously synchronise the rising and falling of heart rate or notice small body language changes. For instance we might hear the other person's breathing or see their chest rise and fall gradually and be able to modify our heart rate accordingly. Other researchers (HeartMath Institute) have suggested that we pick up the changing magnetic field of each other's heart muscles when we are in close proximity to them.


Our own research, detailed below, challenges both these hypotheses because we have evidence that that synchronisation effect persists at distances where sensory cues could not be present and the direct sensing of a heart magnetic field is unlikely to be possible. Our own feeling is that the synchronisation points towards a more profound non-physical sense that we all have that is allowing communication across larger distances.

References: Helm, J.L.; Ferrer, E.; Sbarra,D. Assessing Cross-Partner Associations in Physiological Responses via Coupled Oscillator Models. Emotion, 12, 748-762.

Palumbo, R.; Marraccini, M.E.; Weyandt, L.L.; Wilder-Smith, O. Interpersonal Autonomic Physiology: A Systematic Review of the Literature. Personality and Social Psychology 21(2) 

Click PDF to right to read our latest research report from our Social Coherence Research Day in London, Jan. 2020

Click PDF to right to see some examples of HRV synchronisation from our Social Coherence Research Day in London, Jan. 2020

Non-Local (Distant) HRV Synchronisation Research

This section shows a summary of our own research

Measuring Heart Rate Variability

During the research a number of different heart rate monitors were used, ranging from those that measure the blood pulse as it changes colour just underneath the skin (plethysmography) using an ear clip or using a mobile phone camera, to those that measure the electrical firing of the heart with each beat (electrocardiography). The key parameter measured is the RR interval which is the time delay between pulses or beats. The differences provide a beat-to-beat value of heart rate, which is then graphed to see the changes in heart rate versus time - the heart rate variability (HRV). Standard HRV analysis techniques were used in the research.


Credit Cards
heart rate variablity for different emotions
Changing heartate freqeuncy for different feelings

A posssible heart-to-heart connection between two continents!

Interpreting Heart Rate Variability Signals

The graph with the green line shows a person's heart rate variability (HRV) measured over five minutes while they thought about something frightening, and later while they felt love for their partner. Notice the change in pattern of the HRV from jagged and small variability during fear, to smooth, regular and higher variability during the experience of love. Notice also how the heart rate increases during feelings of love.

Of course other factors can change heart rate such as exercise so in all the experiments we kept as still as we could so we could measure HRV changes caused by emotional effects only.

The next graph shows  heart rate waveform (blue) for a person feeling periods of love towards a partner and periods where their focus was distracted. Notice how the shape of the HR changes character for these two different emotional experiences.

The changes in HRV waveform can be given a value using spectral analysis techniques. The most common, called the Fast Fourier Transform (FFT) estimates how smooth and regular the waveform is by extracting sine waves of particular frequencies (sine waves). High power in the so called Low Frequency (LF) range is associated with feelings of love and positive emotion. More noisy sections of the HRV yield low values and are associated with the experience of fear and negative emotion (see for more information on the link between HRV and emotions).


The green line on the graph indicates the power of the low frequency component divided by the high frequency signal for the experiment. Dividing by the high frequency reduces the impact of movement artefacts. Notice how the LF/HF reliably tracks the periods of feelings of love. In some experiments it was possible to output the low frequency power for both experimenters and look for correlations in these signals - see below for examples.

Experimental Method

The research began as an attempt to scientifically monitor emotional wellbeing for an individual. This then developed to compare two people's heart rates when they are in a loving or bonded relationship. In the early phase of the research the two experimenters were close together within the same room, rarely more than two metres apart.


Later, the research took a radical step and started measuring HRV simultaneously for two experimenters separated by varying distances where sensory feedback was not present. Initially these were carried out without any phone or electronic devices being switched on. These experiments were started with a phone call to synchronise the time zero but these were then switched off for the remainder of the experiment. Data was recorded onto two laptops using commercially available software. Bringing together of the two heart rate signals and analysis was carried out after the experiments had finished.

Later in the research software was developed to allow heart rate data to be recorded, analysed and displayed in real time to a laptop screen for up to three experimenters. This included frequency component data (LF/HF) and allowed a new style of experiments that studied experimenter loving intent versus heart rate or low frequency power for the other experimenters. Examples of these are included below and on the home page video.


Heart connection experiments

Heart rate data was recorded independently at varying distances of separation then analysed for HRV and frequency component correlation


Later research made use of the Heart Bond app that was developed to make it easier to run realtime analysis of HRV synchronisation and the effect of loving intention of HRV synchronisaton

The Results - A Summary
Two Experimenters - Increasing Distance of Separation

Below is a selection of results from the research showing an increasing separation between experimenters ranging from no separation to many hundreds of kilometres. It includes both heart rate variability correlations as well as frequency component correlations.




Married Couple Sitting on Sofa - 1 metre Separation

Overlain heart rates of two people recorded as they sat close to each other watching TV. One person (blue) was feeling love for the other (red).

Several scientific research groups have shown that HRV entrainment is possible in close proximity (up to a few metres separation) for couples in bonded, loving relationships. This entrainment is not evident for pairs of people who are not in a loving relationship. It has been assumed that the mechanism for entrainment is either the mirroring of body language and breathing cues or some form of electro-magnetic (radio) communication between two hearts.


The first phase of our research confirmed the close proximity heart entrainment effect.




heart synchrony for loving couple
Married Couple - Different Buildings - 25metre/80ft Separation

Overlain heart rates for two people in two different buildings, one a house, the other a garden office. No sensory feedback was present. Data recorded via intranet connection into analysis software. Person 1 in the office was focusing love on person 2 while they worked in house.


Notice obvious phase  (general rise and fall of heart rates) correlation.






Two Friends - Across Three Counties - 79 mi/127 km Separation

Same experiment with LF/HF (low frequency/high frequency power) light blue for person 1 plotted against person 2 heart rate, red. Notice correlation of these two signals.

LF/HF is an estimate of how much positive emotion person 1 is feeling towards person 2. This seems to increase the heart rate for person 2 and suggests that one person's loving focus can change another person's heart rate, even at a distance where no sensory information can have been exchanged.







Overlain heart rates for two friends at a distance from each other. No communication devices present. Both experimenters focused love and appreciation for each other.

A clear phase correlation of the heart rates is present for the first half of the experiment, after which the correlations fall away.






Married Couple - Across Southern England - 139 mi/224 Km

Heart rates (top two lines) for two people feeling love for each other. Low frequency power (0.06 hz.) shown on bottom two lines. No communication devices present.

Only moderate correlation visible of heart rates but notice very strong phase correlations on low frequency power up 700 seconds, then loss of correlation. This suggests that the couple were in a bonded state for the first 700 seconds and then lost the bonding for the second half of the experiment.






Married Couple - Both Stressed - 228 mi/367 km Separation

Overlain heart rates for two people struggling to feel love for each other. Both stressed and distracted. Recorded using an ECG heart rate monitor on both experimenters.

Notice no obvious correlation of heart rates.






Married Couple - England to Scotland - 318 mi/512 km Separation

Overlain heart rates for two people feeling love for each other over a large distance. No communication devices present.

Notice strong correlation in first part of the experiment which falls away but then reappears later in the experiment. In the first 400 seconds the heart rates for both experimenters were rising and falling over about 10-12 seconds suggesting that the breathing in and out was also synchronised over this period.








Greatest Separation
Married Couple - California to England, 5356 mi/8620 km Separation

Clear visual correlation of one partner's 1/HF (estimate of loving intent) against other partner's heart rate at very large distance of separation. This experiment was carried out at the Science & Nonduality Conference in October 2016 in San Jose, California where this research was presented formally for the first time.











Two Friends - England to SE Spain - 1000 m/1609 km Separation

Overlain heart rates for friends across a continent. Some heart rate correlation is evident at the beginning of the experiment, it then falls away as person 2 became drowsy, then seems to return as person 2 jolts back fully awake.









Frequency analysis for last experiment. Person 1 low frequency power (LF/HF) plotted against person 2 heart rate.

Notice how person 2's heart rate increases in places where person 1's low frequency power is greatest. This is the same relationship as seen on 25 metre separation experiment shown above and also seen on the results of several other experiments.










Frequency analysis for last experiment. Person 1 low frequency power (LF/HF) plotted against person 2 heart rate.

Notice how person 2's heart rate increases in places where person 1's low frequency power is greatest. This is the same relationship as seen on 25 metre separation experiment shown above and also seen on the results of several other experiments.










Other Research into Nonlocal Heart Entrainment
Conclusions & Discussion

Having now carried out hundreds of experiments over a ten year period, into non-local (distant) heart entrainment and attentional influences, it is clear that the heart rate variability of two people in a loving/bonded relationship can show significant visual and statistical phase correlation. Care has been taken in these experiments to ensure that sensory cues were not available for the experimenters (except in cases of close proximity or where loving intent was being investigated). The following explanations and hypotheses have been considered to explain the correlations.

1) The data is made up - you will have to take our word on this, it isn't! Better still why not run some of your own experiments. See 'How to get involved'.


2)  The correlations are chance line-ups and are caused by beating of basically sine wave HRV signals. This is always a possibility with harmonic data such as HRV but the strength and regularity of the correlations even where the frequency changes suggests that this is not the full explanation.


3) The recording method is unreliable and has introduced apparent correlations - unlikely as many datasets were recorded independently into individual laptops. Different heart rate monitors have been used and the correlations are still evident suggesting they are not device-dependent.


4) The analysis was inaccurate or introduced correlations. While human error is inevitable in some cases, it is unlikely that this is the explanation for every example of correlation. The analysis in most cases was a simple plotting of two heart rates signals. This was carried out with great care.

Different frequency analysis software was used to check that the software was not introducing the correlations - the correlations were still  apparent using different software packages that used different spectral analysis algorithms.


5) The correlations are simply the result of natural breathing patterns that now and again line up, especially at the beginning of each experiment. While this might be happening in some experiments it does not explain the distinct step change correlations, nor the variable character of the HRV correlations.


6) The correlations are genuine  but are caused by a third party effect - i.e. something like the earth's fluctuating electro-magnetic field is controlling both hearts and causing them to correlate. This has not yet been investigated but if true, would be a significant scientific discovery as it would suggest that all humans are connected and affected  by such a field. See research by the Heartmath Institute for their ideas about human heart coherence. The results of the loving intent experiments would argue against there being a third-party effect as there is clear change in HRV for both experimenters that is not controlled by a third-party effect (unless our free will is somehow controlled by the third party effect!)


7) The correlations are genuine. Hypotheses to explain such correlations include:

a) There is no communication between hearts/brains/bodies - each person senses a changing global or regional field such as the earth's magentic field and their hearts beat with similar patterns. Could be tested with suitable magentic shielding.

b) Communication between hearts/brains via the electro-magnetic field generated by the heart muscles - Heartmath Institute's preferred explanation for close proximity entrainment. This seems plausible at close proximity but is harder to accept at large distances of separation.

c) Communicatin between people using the earth's magnetic field - requires that  humans can encode information in the earth's magentic field. Currently no scientfic theory exists that could explain this, but experments are being carried to explore possibility that collective positive intent (love) is linked to global changes in the earth's magentic field and that this is also reflected in collective changes in HRV.

d) A quantum mechanics effect  - quantum entanglement of cells of the two hearts/brains and communication through the wave function. (Nonlocal, Action at Distance).

e) A completely new field or force unknown to science. 

f) Communication/Entrainment via a connected non-dual consciousness, mechanism could be quantum in nature, as in d., or as yet unknown to science.    



Very few studies into nonlocal heart entrainment have been conducted and so far we have not found any that have been published as peer-reviewed scientific papers. The only previous study we have found to date is the Phd Project by Dorothy Mandel in 2007. Her dissertation decscribes a laboratory-based research project into nonlocal human connectedness which studied heart rate variability measures of pairs of people.

The results of this research showed that one person could influence (raise) the heart rate of another who is at a distance and isolated from sensory and electromagentic cues through positive/loving intent. The results also showed a pre-sentient effect in that the 'receivers' heart measures changed prior to the onset of the 'senders'  positive intent. It was recommended that more resarch be carried out.

See abstract












Mandel, D. (2007) Correlated heart rate measures in the study of nonlocal human connectedness. Phd. Dissertation

(Research partner Kozak, L.)











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