This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Symptoms & Signs , Subject name: Psychiatry
Definition of hallucination - 
Select and explain. 
A. Perception without stimulus, B. Alteration of perception of a real stimulus, C. Change in Intesitity of a real stimulus, D. Misinterpretation of a real stimulus
A: Perception without stimulus
Answer: A: Perception without stimulus 
Explanation: Ans. is 'a' i.e., Perception witout stimulus o Disorder of perception may be : -Altered perception : - There is alteration of preception of a real external stimulus. It may be : -Sensory distortion : - There is change in the intensity of a real external stimulus. For example micropsia (perceiving a real object smaller than its normal size) and hyperacusis (perceiving sounds as abnormally loud).Illusion : - There is misinterpretation of a real external stimulus. For example mistaking a stick for snake.False perception : - There is an internal perception without a real external stimulus, e.g., Hallucination and pseudo-hallucination