<prompt> All of the following are features of hallucinations, except :It is independent of the will of the observerSensory organs are not involvedIt is as vivid as that in a true sense perceptionIt occurs in the absence of a perceptual stimulus  <response>: Hallucination is a sensory perception without external stimulation of the relevant sensory organ. Though there is no stimulation of sensory organs, hallucinations appear to arise from one of the external sensory organ. 