The
plantar reflex is a
reflex elicited when the sole of the foot is stimulated with a blunt instrument. The reflex can take one of two forms. In normal adults the plantar reflex causes a downward response of the
hallux (
flexion). An upward response (
extension) of the
hallux is known as the
Babinski response or
Babinski sign, named after the neurologist
Joseph Babinski. The presence of the Babinski sign can identify
disease of the
spinal cord and
brain in adults, and also exists as a
primitive reflex in
infants.