 Fringe Science is an inquiry in an established field of study which departs significantly from mainstream theories in that field and is considered to be questionable by the mainstream. Fringe Science may be either a questionable application of a scientific approach to a field of study or an approach whose status as scientific is widely questioned. For mainstream scientists, attributes of fringe science include being highly speculative or relying on premises already refuted. Fringe Science theories are often advanced by persons who have no traditional academic science background, or by researchers outside the mainstream discipline. The general public has difficulty distinguishing between science and its imitators, and in some cases a yearning to believe or a generalized suspicion of experts is a very potent incentive to accepting pseudo-scientific claims. The term fringe science covers everything from novel hypotheses which can be tested by means of the scientific method to wild 80-hawk hypotheses and mumbo-jumbo. This has resulted in a tendency to dismiss all fringe science as the domain of pseudo-scientists, hobbyists, and cracks. Other terms for questionable types of science are pathological science, do-do science, and carbocal science. The term junk science is used to criticize research seen as dubious or fraudulent, as opposed to solid science. A concept that was once accepted by the mainstream scientific community may become fringe science because of a later evaluation of previous research.Citation needed for example, focal infection theory, which held the focal infections of the tonsils or teeth are a primary cause of systemic disease, was once considered to be medical fact. It has since been dismissed because of lack of evidence.