Psychology says people who go very still when they're upset, no fidgeting, no shifting, almost no movement, aren't calm or indifferent; they're often the ones for whom stillness became the only safe response to something overwhelming

Going completely still during upset is often a freeze response, not composure. The nervous system activates freeze when fight or flight is impossible. This survival habit often forms in childhood when expressing emotions was unsafe. Stillness can mask terror, dissociation, and a body running an old protective program.