Two nervous systems.

Closeness is one layer of a relationship. Beneath it runs a second: how wound up or wound down each of you is at any moment. This lesson shows how that level decides whether you can think and be kind, and how partners keep moving each other up and down.

What arousal means

Tatkin now sets attachment aside and talks about arousal. He does not mean sexual arousal. He means how activated your nervous system is, on a scale that runs from highly excited to deeply relaxed.

Both ends hold good states and bad ones. High up you find thrill, excitement and bliss, and also fear, terror and rage. Low down you find relaxation, quiet reflection and meditation, and also depression and shame. All of it is normal, and a full life visits the whole range.

This layer is separate from the styles of lessons 3 and 4. An island, a wave or an anchor can each run high or low.

Airplanes and submarines

Some people live mostly at one end. Tatkin calls them airplanes and submarines. Like the attachment styles, these are lifelong leanings that tend to run in the family. Someone who suddenly starts living at the high end is a different matter, and he says that calls for medical attention.

The speeds differ. An airplane comes down faster than a submarine comes up, so people at the low end usually need longer to get back to level.

The two are often drawn to each other. The airplane finds the submarine grounding and real. The submarine finds in the airplane the colour that is missing from their own life. The catch is that a person who lives high up makes life harder for a partner who does not.

The window of tolerance

Between the extremes lies a middle range in which you can think, listen and relate. Tatkin borrows the name window of tolerance from Dan Siegel and Pat Ogden, and also calls it the social engagement system.

His explanation of why thinking fails outside it is about fuel. The fast, automatic brain from lesson 1 runs on memory and is cheap to run, so it keeps going under stress. The slow brain, the part that weighs things up and finds answers that fit the situation, burns a great deal of oxygen and glucose. Inside the window there is enough for the whole brain. When you feel threatened the window narrows, you slide out of it, and the costly slow brain goes short.

Freeze and collapse are easy to mix up. Freeze belongs at the top. It is a split second of locking, like a deer caught in headlights, before you fight or run. Collapse belongs at the bottom, and can look like someone who retreats to the bedroom for days.

Two questions follow. Which way do you tend to go in conflict: fight, flee or collapse? And how quickly do you come back? Tatkin mentions, without naming a study, that the average person needs 20 to 30 minutes to recover fully from fight or flight. Some people stay angry for hours and stop only when they are worn out, which he says is hard on the body and on every relationship.

Partners regulate each other

Tatkin says partners in a close bond are wired together. When one shoots up, the other follows. When one sinks, the other sinks. If you are slow to recover, your partner will be slow too.

From this he draws the conclusion that sets the program apart from most self-help. Its subject is not calming yourself. You should know how you work and own it, but under stress you will go on doing what you do. What can change is how well your partner handles it, and how well you handle theirs. His term for this two-way process is interactive regulation.

So each of you needs to know the other's pattern: how to head it off, and how to shorten the episode once it has started. He wants partners to become experts on each other and good managers of each other, because nobody can do this alone.

Tortoise and hare

A third layer sounds similar but is different again: how fast you process emotional material, about yourself and the relationship, when you are under stress with someone close. A hare does this quickly. A tortoise does it slowly. Intelligence does not come into it. Very bright people can be tortoises.

Do not confuse a tortoise with an island. An island talks at normal speed until the subject is themselves or the relationship, and then weighs every word for fear of getting into trouble. That is caution. A tortoise really does need more time to take the information in.

Put a hare with a tortoise and you get an unfair fight. The hare runs rings round the tortoise, who ends up feeling beaten or flattened. The tortoise cannot be made faster. So the responsibility sits with the hare: stay aware, in the middle of a conflict, that you are outrunning your partner, and take care not to.

Runaway threat

What ties these layers together is threat. If you do not understand yourself or your partner, and do not know how to keep things friendly and playful enough, small moments of danger pile up. Hurts go unnoticed or are not repaired quickly. One of you does what suits them without checking that it suits the other. Over time the sense of danger repeats and grows.

Tatkin calls this runaway threat. It ends as fear kindled in the body, far beyond the reach of reason. As evidence he cites a study he attributes to John Gottman: ex-partners with a bitter divorce behind them showed a raised heart rate from simply sitting in a room together. People who once loved each other come to see each other as predators.

He insists that these are not bad people and that nobody sets out to end up there. It is what happens naturally when you do not know better, above all if your own parents never learned to look after each other. It is also fast. Couples tell him they were chatting along and then, with no idea how, found themselves backed into a corner again. He asks you to respect that speed.

Match, then shift

In session 3 Tatkin returns to the nervous system with one practical rule. You cannot move a partner up or down while you are far from them in arousal. From a distance you do not calm or cheer them. You come across as a threat.

So you go to where they are first. With an airplane partner who is flying high, raise your own energy to somewhere near theirs. Then either play with them up there or bring them down bit by bit. Staying flat and still will not do it. With a submarine partner who is low, bursting in bright and jolly pushes them further down. Come near their level, then lead slowly up.

He adds two cautions. A partner who goes from calm to full speed in an instant, or who stays far down for long stretches, may need medical or psychiatric attention, although you still have to deal with it in the moment. And the window is not fixed. Medication, alcohol and other drugs, too little sleep, pain and illness all narrow it for a while. Those effects pass. What you are learning here is your partner's lasting style.

About the model: Airplane, submarine, tortoise and hare are Tatkin's teaching images, and the fuel explanation is his simplified account of the brain under stress. Recovery times differ widely from person to person.