Maxwell Maltz was a plastic surgeon in the 1950s when he began noticing a strange pattern among his patients.
When Dr. Maltz would perform an operation — like a nose job, for example — he found that it would take the patient about 21 days to get used to seeing their new face. Similarly, when a patient had an arm or a leg amputated, Maltz noticed that the patient would sense a phantom limb for about 21 days before adjusting to the new situation.