The Sandman Effect

Co-regulation gone bad. On bio-behavioural synchrony, psychotherapy, emotional contagion and the Sandman Effect.

Say your prayers, little one

Don't forget, my son

To include everyone

I tuck you in, warm within

Keep you free from sin

'Til the sandman, he comes

(Enter Sandman, Metallica)

As it turns out, phrases like “we are in sync” or “we are on the same wavelength” are more than just metaphors. They are actually linked to the eerie, but very real, phenomenon of bio-behavioural synchrony. In this case, the intuition, and the language that emerged from it, got it surprisingly right.

While we tend to romanticise this capacity to be in sync with someone, it has its darker side.

Follows the story of the eerie phenomenon of bio-behavioural synchrony and its darker side, the Sandman Effect.

Being In Sync Is More Than A Mere Metaphor: What is Bio-Behavioural Synchrony?

"Why people ‘‘click’’ with some people but not others is one of the great unsolved mysteries of science. However, researchers from psychology and neuroscience are converging on a likely physiological basis for connection – neural synchrony ( or entrainment)".

The quote above talks about neural synchrony, which is part of a broader phenomenon called bio-behavioural synchrony. Bio-behavioural synchrony is defined as temporal alignment (or synchronisation) of biological and behavioural parameters during interpersonal interactions. Four aspects of bio-behavioural synchrony have been well-documented:

• Behavioural (synchronisation of body movements)

• Physiology synchrony (examples: heart rate coupling, pupil dilatation synchronisation)

• Endocrine synchrony (examples: coordinated cortisol stress response, coordinated oxytocin parent/child, romantic partners)

• Interbrain synchrony: the brain activities become aligned or “in sync”

Right, would you believe this? As we spend time together, and especially under certain circumstances, particularly when we are engaged in a shared endeavour - we just tend to spontaneously synchronise.

We synchronise in gestures and behaviour, hormone levels, heart rate, brain waves, and even patterns of brain activation. Even our pupils dilate in sync during moments of shared attention (additionally, that shared attention can be tracked through eye contact).

Some researchers have even suggested that bio-behavioural synchrony could be a key mechanism in how we fall in love.

Now, there is a lot of nuance here. Not everyone synchronises in the same way (people who are closer tend to do so more easily, the extent of synchrony indicating the strength of the relationship) and not all activities are equally conducive to it. Still, generally speaking, we do synchronise and we love doing it.

I think that’s crazy. Pure madness, even. Enough to give tons of heavy ammo for any New Age aficionados who can finally say: “See? We’ve known it all along. It’s just that neuroscience is finally catching up. It's all about frequencies”. Ammo or no ammo, you’ve got to honour just how wild and subtle all of this is - along with how far we have come in being able to measure, characterise, and study what is, at heart, a subtle and non-verbal form of communication.

In a nutshell, with bio-behavioural synchrony, we embody, or come as close as possible, someone else’s emotional state. It is the proverbial other person's shoe.

Needless to say, this is all so fascinating on so many levels for psychotherapists.

Being In Other Person's Shoes - How To Get In Sync?

Generally speaking, we are suckers for synchrony. In fact, we love synchrony so much, that we value the feeling of being in sync even when it gives us no useful information. Some of us are just synchrony junkies!

Whether getting in sync is always a good idea is highly debatable. In fact, that is the whole point of this piece, as you shall se if you bear with me until the end. But, if we wanted to, what could we do to become more synchronised with another?

It Just Happens Well, for starters, it happens spontaneously. As we spend together, especially is we do something together, bio-behavioural synchrony just happens. Not everyone at the same rate, not always, but we do, generally speaking, synchronise.

Eye Contact, Locking Gaze They say that if you lock eyes with someone for four minutes, they’ll fall in love with you. I remember hearing that in high school, a sort of on-demand love spell. And while I’m not sure it’s entirely true, it does illustrate an important point: direct eye contact is a powerful way to connect.

Which is exactly why we so often avoid it. Staring into someone’s eyes can feel like staring into the sun. It can create the sensation of fading into the other person (just as Mazzy Star sings).

But coming back to bio-behavioural synchrony, I believe a healthy (but non-creepy) dose of direct, friendly eye contact can go a long way in fostering synchrony between two people. The evidence abounds. And it almost certainly plays a role in love spellbinding too, for those so inclined.

Laughter I don’t have any hard evidence to give you here, but I’d bet my top dollar that a good, shared, wholehearted laugh gives synchrony a good boost.

Shared intentionality Doing things together towards a shared goal (aka shared intentionality) can foster greater synchrony - and vice versa. This is also true when it comes to children/parents synchrony.

Finding Common Ground Lacking common ground can be a killer to developing synchrony. When getting to know someone new, whether it’s a client in a psychotherapy setting or simply someone we have just met, building some shared ground can help foster and sustain synchrony.

The examples above are just a few strategies that can be easily put into practice. Music, dancing, and countless other experiences - many more than I can even begin to imagine - are available to help us move into greater states of synchrony. But let’s now move from the question of How to the question of Why of bio-behavioural synchrony.

The Closest We Get to Reading Other People's Minds - The Why of the Bio-Behavioural Synchrony?

From: Animal Magnetism

The bio-behavioural synchrony has been termed the 'social glue', and when people’s brains and bodies are more in sync, they tend to understand one another better.

Some of you might remember my post titled The Devil You Know: The Free Energy Principle and Psychotherapy. In that piece, I explained - in layman’s terms and with a psychotherapy focus - the active inference framework.

In a nutshell, this is a way of understanding the brain as a biological 'device' that makes inferences about reality, and especially the aspects of reality that are relevant to the organism. It does so by drawing on both external and internal information, as well as, crucially, its own past experiences.

For those who dabble in the statistical or mathematical arts, this might sound familiar: it’s essentially Bayesian inference account of the brain.

And of course, when it comes to the external world, for every human other humans are a major factor. Other humans are our biggest blessing as well as our biggest curse. Anticipating their actions becomes then a central task and arguably a massive one. In fact, it’s likely that large portions of the brain are dedicated to decoding and predicting the behaviour of other complex human brains' decisions and actions.

Now, let's go back to the bio-behavioural synchrony. Within this active inference framework, it is easy to see how the synchrony comes in handy. Because if your brain is synchronised with mine - if your physiology and overall state of arousal are similar to mine - then chances are we’ll think, react, and behave in similar ways.

Since I know what I am doing, if we’re synchronised in some of these ways, it becomes much easier for me to predict YOUR behaviour. And remember, predicting the behaviour of others is absolutely vital for humans - after all, other humans are our natural habitat.

As you can see, active inference and bio-behavioural synchrony - it's hand in glove. Pretty neat, I must say.

But of course, engaging in synchrony is a two-way street, right? If, through synchrony, we gain easier access to someone’s internal states and better chances of predicting their behaviour, the same applies the other way around. So, should we - or even can we - grant that level of access to everyone?

That’s exactly where the Sandman Effect comes into play.

Spellbound: The Sandman Effect

While bio-behavioural synchrony is usually hailed as a positive and pro-social phenomenon, it is in fact neither inherently good nor bad. In reality, it’s a double-edged sword.

After all, embodying someone else’s affective state is only beneficial if it’s something we want to experience. By allowing someone to influence our inner states so directly, we open the door to both connectedness and negative and deeply uneasy affect.

It’s like a Trojan horse in our inner emotional sanctum. We need to be careful who we let in.

Enter Sandman.

The Sandman is a mythical character originating from Central and Northern Europe. He is the master of sleep, dreams, and nightmares, endowed with a magical bag of sand. When he sprinkles this sand into someone’s eyes, that person falls asleep.

The Sandman is neither malevolent nor benevolent - he is morally ambiguous. As the master of dreams and nightmares, if you fall asleep in his presence, he gains the special power to control your dreams. That is when the Sandman’s dark side can emerge, as you lose control over your own dreaming.

As with the Sandman and dreaming, so it goes with synchronising to someone else’s emotional state.

As I said before, synchrony is a double-edged sword.

Fading into someone can lead to becoming more emotionally aligned generating a feeling of closeness, deeply pleasant, sometimes transcendental.

Other times, it can drag us down into places we don’t want to go. Becoming aligned emotionally in times when we are not up for it, or when the person we find difficult to emotionally tolerate because of the complex emotional history behind (such an problematic attachment figure) can feel like a poisoned gift that we didn't ask for, but that sticks and we can't get rid of. It is borrowed feelings we don't know what to do with. It is emotional contagion. It is are vicarious unease and distress.

Sometimes for better, sometimes for worse - with bio-behavioural synchrony, we are, in a sense, spellbound.

Sandman effect, it's co-regulation gone bad.

Take Home Message: Take Only What You Want (and Can) Take

Hopefully, by now I have convinced you that more synchrony is not always better. Even when it comes to attachment, exciting new research challenges the narrative a 'more is better' when it comes to bio-behavioural synchrony.

Being permanently wired into another person’s internal emotional states and levels of arousal might sound like a superpower but in reality it comes at a great cost (we might even call it the Sandman tax). Research shows that individuals who display greater physiological alignment with their partners tend to have less stability in their own physiological states.

This is especially relevant for therapists of all stripes, for it is woven into the very fabric of our profession to connect emotionally. In fact, it is one of the most important tools at our disposition. But it is also our Achilles' heel and a serious risk of our profession: the Sandman Effect quietly creeping in - through alien affect and vicarious distress. It is NOT to be taken lightly.

I hope that, after reading this, for both therapists and other humans alike, I have given you the permission to take only what you want and what you feel you can hold. Even if they’re invisible, feelings are real (and really contagious).

The next time someone tells you: No one can make you feel anything, you can confidently reply: In fact, yes, they can. Behold the Sandman Effect.

As always, thank you for reading. You can follow me on BlueSky , via my substack or subscribe to my mailing list.

---

Some Interesting Readings On the Topic

• Brain Waves Synchronize when People an accessible piece about interbrain synchrony

• Visualizing the invisible tie: Linking parent–child neural synchrony to parents’ and children's attachment representations

• In and out of synchrony - Behavioral and physiological dynamics of dyadic interpersonal coordination