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How to determine if my sympathetic or my parasympathetic nervous system is currently dominant?

bycrabman2mo31st May 20195 comments

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I've been reading CFAR Handbook's chapter about Againstness. The chapter's idea is that when your sympathetic nervous system (SNS) is dominant over parasympathetic nervous system (PSNS), your introspection is impaired and you tend to be less rational, hence you should learn how to know which system is currently dominant and also learn to switch to PSNS dominance.

They provide the following table of how your body, mind, and behaviour change depending on which system is dominant

table sns vs psns

In order to learn to know where you are on SNS-PSNS spectrum they recommend observing yourself in different situations, determine which system is dominant, and try to find patterns (e.g., maybe after doing physical exercise your SNS is usually dominant).

Well, I tried observing myself and figuring out which nervous system is active, and about 70% of the times I can't determine it. I ask myself questions like "Do I feel joy?", "Am I at peace?", "Are my muscles tense?", "Does my skin feel like flushed?", "Is my breathing shallow, or slow and in belly?". More often than not I can't answer these questions. And it doesn't help that there's no easy way to calibrate by observing the ground truth.

If there are people here who can determine which of your two nervous systems is dominant, how do you do it? Any tips for me?

Also, sometimes I get signals from my body that don't fit in this framework. When it's time for me to go to sleep but I don't do it, after a while my awareness and introspective clarity become impaired, I feel both energized and lacking energy at the same time, I fill like my system 2 (as in Kahneman's two systems) doesn't turn on a lot, and I get impatient. What happens with SNS and PSNS at this time? I don't know.

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4 Answers

I'm not 100% confident in this, but many people cite heart rate variability as a sign of high PSNS activity, especially when the heart rate itself is not elevated.

I like Elizabeth's answer of HRV because it's supported by the literature, quantifiable, and pretty easy to measure with an external tools. In your case, I think if you're asking questions like "what muscles are tense?" or "How do I feel right now?" and not getting a response, it may be simply lack of practice in certain types of awareness.

Mindfulness based meditation around body, breath, and mind awareness are deliberate practice towards being able to answer those questions.

Quick answer: You can apparently use a Galvanic Skin response meter for this, though I have only experimented with one for about 10 minutes, and can't give you first-person verification.

We had the topic of SNS and PSNS recently on a bodywork workshop and one of the points that was made there is that most people in our society are likely too much in SNS and not enough in PSNS.

On the other hand, setting being in PSNS as the goal can also lead to being all the time in a low energy state. If you want to get things done in the world, it's useful to also be able to operate in SNS mode.

When it comes to measuring, I get the impression that measuring HRV gives you a more useful signal then Galvanic Skin response.

It would be great to have an app that trains you to do credence calibration on your HRV.