Columbia Encyclopedia:
gooseflesh,
temporary rumpling of the skin into tiny bumps, also called goose bumps and goose pimples, and technically known as cutis ansirina. In response to cold or certain emotional states, such as fear or rage, the smooth muscles of the subsurface layer (dermis) of skin tend to contract, causing the skin to pucker and body hair to stand erect. In furred animals this can serve a dual purpose. Erection of the fur may make an animal seem larger than it actually is and act to frighten away a potential aggressor. Second, the erect fur traps a blanket of air close to the skin thus providing the organism with additional insulation against loss of body heat. In humans, this response would seem to be vestigial.
