A hallucination involves the perception of something (a vision, a sound, a smell) that is not physically present. They exist of many types. There are hypnagogic hallucinations , which occur when a person begins to fall asleep and include sensations of falling and tripping on a ladder, while others appear on waking ( hypnopompic ). Chromatopsia consists of seeing all people and all things with the same color. And when it comes to size, patients with Lilliputian hallucinations see tiny objects and subjects, while victims of Gulliveresque hallucinations see the opposite. Dysmegalopsia consists of visualizing objects with unusual or irregular shapes.
Kinesthetic hallucinations that affect internal visceral sensitivity – for example "feeling" the flow of blood in blood vessels – are very common.
