Fish have no necks, yet this ancient balancing trick keeps their heads startlingly steady in motion

Postural control is a fundamental behavior for most animals, and head stability in particular plays a crucial role in achieving stable sensory input, accurate spatial perception, and efficient motor output. Tetrapods, including humans, possess a "neck"—a structure that separates the skull from the trunk skeleton—and stabilize their head in space by contracting and relaxing neck muscles in response to body tilt. This reflexive mechanism is known as the vestibulo-collic reflex.