Denial is a defense mechanism postulated by Sigmund Freud, in which a person is faced with a fact that is too uncomfortable to accept and rejects it instead, insisting that it is not true despite what may be overwhelming evidence. The subject may deny the reality of the unpleasant fact altogether (simple denial), admit the fact but deny its seriousness (minimisation) or admit both the fact and seriousness but deny responsibility (transference). The concept of denial is particularly important to the study of addiction. The theory of denial was first researched seriously by Anna Freud. She classified denial as a mechanism of the immature mind, because it conflicts with the ability to learn from and cope with reality. Where denial occurs in mature minds, it is most often associated with death, dying and rape. More recent research has significantly expanded the scope and utility of the concept. Elisabeth Kübler-Ross used denial as the first of five stages in the psychology of a dying patient, and the idea has been extended to include the reactions of survivors to news of a death. Thus, when parents are informed of the death of a child, their first reaction is often of the form, "No! You must have the wrong house, you can't mean our child!"