<P> The formation of goose bumps in humans under stress is considered to be a vestigial reflex ; 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 . </P>
<P> The formation of goose bumps in humans under stress is considered to be a vestigial reflex ; 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 . </P>
goose bumps are caused by action of the
goose bumps are caused by action of the
pilomotor reflex
pilomotor reflex