Reflex

A Venus flytrap doesn't snap shut on the first touch. One trigger-hair touch arms the trap; a second within 20–40 seconds fires it. This avoids wasting energy on raindrops or debris. A third touch in the window signals struggling prey and starts digestive enzymes.

Submerging your face in cold water triggers the "diving reflex." Heart rate drops 10-25% and blood flow shifts to protect the brain and heart. This ancient mammalian reflex is especially strong in babies under six months.