Illusion - a distorted and incorrect perception of real objects. Especially often illusions arise on a background of depression with anxiety or fear, and the lack of clarity of perception associated with the deterioration of the activities of the senses (hearing, sight, etc.,). A typical example of the illusion that occur in healthy people, is a distorted perception of the surrounding objects at night in the forest cemetery, (Bush seems to be lurking man and so on). When mental illness illusions arise mainly at the initial stage of acute psychosis. Thus there are both visual and verbal illusion. For example, shiny object in the hands of a stranger seems like a knife, in a conversation around the extraneous subject heard threats, name-calling to the address of the patient, and so on, Sometimes patients, looking at the Wallpaper, cracks in the wall, seeing the colorful pictures, scenes of fantastic content, figures of people, animals (parabolicheskie illusion). In the development of acute psychosis often the whole environment is perceived incorrectly (illusory), with the illusion combined with delirium (acute schizophrenia, toxic, infectious psychosis).