1. Babinski's sign is a clinical test where a pointed instrument is run up the lateral border of the foot and over the metatarsal pads, eliciting an extension response in the big toe in patients with upper motor neuron lesions. 2. Joseph Babinski discovered this sign in 1896 while working as a student of Jean-Martin Charcot at the Salpêtrière Hospital in Paris. 3. Babinski's sign indicates damage to the corticospinal tracts in the brain or spinal cord, and a positive result often prompts further neurological examination.