Complex sentence: Several scientific principles can be used to explain reports of shadow people, including optical illusions or hallucinations brought on by physiological or psychological circumstances, drug use or side effects of medication, and the interaction of external agents on the human body.
Split into simpler sentences: Several scientific principles can be used to explain reports of apparitional experiences such as shadow people. These include optical illusions or hallucinations brought on by physiological or psychological circumstances, drug use or side effects of medication, and the interaction of external agents on the human body.