goose bumps are caused by action of the
Goose bumps The formation of goose bumps in humans under stress is considered to be a vestigial reflex;[2] and its function in other apes is to raise the body's hair, and would have made our human ancestors appear larger to scare off predators or to increase the amount of air trapped in the fur to make it more insulating. The reflex of producing goose bumps is known as piloerection or the pilomotor reflex. It occurs in many mammals besides humans; a prominent example is porcupines, which raise their quills when threatened, or sea otters when they encounter sharks or other predators.