When the body senses danger, it reacts before the conscious mind can catch up. In this video, I break down how the sternocleidomastoid muscle in the neck tightens to protect the carotid artery during the earliest stage of the freeze–flight–fight response. This automatic, limbic-driven reaction often appears before any facial expression or microcue of fear.

If you want to understand threat signals, emotional stress, or early fear indicators in real-time, this is one of the most reliable cues to watch for.