Demonstrating that there has long been a recognized need for a purported invention, can, in the United States, support the non-obviousness requirement for a patent on the premise that given the need and an obvious solution, persons of ordinary skill in the art would have fulfilled it without the need for invention. U.S. commentators typically defend the evidentiary use of long-felt-need by the argument that true genius may lie in spotting an simple solution overlooked by others. Long felt need is sometimes referred to as a secondary indicia of non-obviousness.