Hallucination refers to a kind of real and vivid perception without objective stimulation acting on the corresponding senses. Hallucination is a kind of perceptual disorder, mainly including auditory hallucination, visual hallucination and touch hallucination. It mostly occurs in the state of psychosis. Normal people may also appear sometimes under the conditions of tension, fatigue and high fever.
According to the above definition, which of the followings is an illusion?
Xiaofeng watched TV at home, as soon as his mother left for work. But he always felt that he heard his mother's footsteps from time to time.