You have had this session. A client who is normally sharp arrives unable to hold a thought. They circle, contradict themselves, cannot answer a straightforward question. Or the reverse: flat, distant, agreeing with everything and taking nothing in.
Neither is resistance, and neither responds to better questions. Dan Siegel's window of tolerance describes what is happening, and it is one of the more practically useful models a coach can carry — with an important boundary attached.
The Model
Everyone has a range of nervous-system arousal within which they can think clearly, feel appropriately, and take in new information. That is the window.
Above it — hyperarousal. Anxious, racing, reactive. Threat-response is dominant, and the parts of thinking that handle nuance and long horizons are the first to go.
Below it — hypoarousal. Flat, numb, disconnected, foggy. Often mistaken for calm, and frequently mistaken for agreement.
The window is not fixed. It narrows under stress, poor sleep, and cumulative load — one reason the sleep and mood relationship shows up in coaching far more than clients expect.
Why It Matters in Coaching
Because coaching only works inside the window.
Insight, reframing, planning, commitment — all of it requires the capacities that go offline at either edge. A client outside their window cannot use a good question, and pressing harder pushes them further out. Most sessions that "went nowhere" were sessions spent outside the window, and both people usually leave thinking the problem was the content.
Spotting Each Edge
Above: faster and higher speech, jumping between topics, catastrophic framing, absolutes, difficulty finishing sentences, visible physical restlessness.
Below: longer pauses, shorter answers, flat delivery, "I don't know" as a reflex, agreeing readily with everything, a sense that you are doing the work alone.
Hypoarousal is missed far more often, because it presents as a cooperative and low-friction session. If you leave a call feeling you did all the lifting, consider that the client may not have been there.
What to Do
Change what the session is for, rather than trying harder.
Above the window: slow and narrow. Shorten your sentences. Ask for one concrete thing rather than an exploration. Come back to the immediate and specific — what happened, in what order. Concrete detail is regulating; abstraction is not.
Below the window: increase engagement gently. Ask about something with texture — what they had for breakfast, what the room they are in looks like. Slightly more energy in your own voice. Movement helps if it is available.
Either way, name it without diagnosing: "You seem quite wound up today — do you want to use this differently?" Most clients are relieved, because they knew and could not say.
A session spent helping someone come back into their window is not a wasted session. It is frequently the most useful hour of the engagement.
Using It Between Sessions
The model's real value is longitudinal. A client whose window has been narrowing for three weeks needs a different conversation from one having a bad Tuesday — but from inside a fortnightly session you cannot tell those apart, because you only see the day you meet.
Simple capacity and energy ratings collected weekly make the difference visible, which is why they are the leading indicator recommended in tracking progress without admin. A narrowing window shows up as declining capacity well before it shows up as a missed commitment.
The Boundary
This model comes from trauma therapy, and borrowing the map does not make you a therapist.
Use it to understand what is happening in the room and to adjust how you work. Do not use it to treat, to explore trauma history, or to explain a client to themselves in clinical terms. If someone is regularly outside their window, or if what surfaces at either edge is clinical in nature, the appropriate move is a referral — and doing that well is a mark of competence, as the scope clause in your coaching agreement should already have made straightforward.
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