Areas › Your body › Your nervous system
Breathing that has gone almost invisible happens in both kinds of stillness, so it will not tell you which one you are looking at. Muscle tone will.
Look at the jaw, the hands, the shoulders, the way the body is being held in the chair. Tight and set is one thing. Slack and heavy is another. You can see it from across the room, and you can catch it in yourself in the middle of a hard conversation. Asking the person is still better than guessing, whenever they are able to answer.
Qur’an and Sunnah
'He gave you hearing, sight, and minds' (Quran 32:9). Looking carefully at another person is an ordinary use of what you were given.
ثُمَّ سَوَّىٰهُ وَنَفَخَ فِيهِ مِن رُّوحِهِۦۖ وَجَعَلَ لَكُمُ ٱلسَّمۡعَ وَٱلۡأَبۡصَٰرَ وَٱلۡأَفۡـِٔدَةَۚ قَلِيلࣰ ا مَّا تَشۡكُرُونَ
Then He moulded him; He breathed from His Spirit into him; He gave you hearing, sight, and minds. How seldom you are grateful
Qur’an 32:9read it in the library
Translation: M.A.S. Abdel Haleem, The Qur'an, Oxford University Press, 2004.
What the research says
A methodological review of heart rate variability makes a related point about physiological signals in general. The measure does index the parasympathetic contribution to how the heart is controlled, and that contribution is linked to self regulation, but most of the review is about how easily the number is confounded by breathing, posture, movement and collection method. One reading is rarely enough. That review is about laboratory measurement rather than about reading a person in a room.
Laborde S, Mosley E, Thayer JF. (2017). Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research - Recommendations for Experiment Planning, Data Analysis, and Data Reporting.. Frontiers in psychology doi
Strength of evidence: one line of research. A single study, or a theoretical account.
Why it works
One signal on its own can be produced by opposite states, so you need a second one to tell them apart.
This one is still a draft. It is waiting on a scholar and a clinician to read it before it is published.
Near this one
You do not have to read your child perfectly. Good enough, with repair after the ruptures, is what builds their steadiness.
There is a difference between not being upset anymore and actually being settled. The first is a rough tuning. The second is finer.
Coming up out of numbness usually feels worse before it feels better. Restlessness, irritation and a jumpy stomach are often the way up rather than a relapse.