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
Illusion is a disorder of- 
Select and explain. 
A. Thought, B. Perception, C. Memory, D. Intelligence
B: Perception
Answer: B: Perception 
Explanation: Ans. is 'b' i.e., Perception Disorders of perceptiono Altered perception:- Sensory distortion (micropsia, hyperacusis), Illusiono False perception:- Hallucination.Thought disordersFormal thought disorders (Disorders of thought process)Disorders of thought contenti) Racing thoughts:- Anxiety, Schizophreniaii) Retarded thoughts:- Depressioniii) Circumstantiality:- Mania, Schizophreniaiv) Thought blocking Schizophrenia, Severe anxietyv) Perseveration:- Organic brain disease, Schizophrenia (occasionally)vi) Loosening of association:- Schizophreniavii) Flight of ideas:- Maniaviii) Tangentialityix) Clunging & punning:- Mania & schizophreniax) Neologism, word salad, Echolalia:- Schizophreniai) Delusion:- Psychosis (Schizophrenia, mania, depression & othersii) Obsessioniii) Compulsioniv) Preoccupationsv) Phobiasvi) Depersonalization & Derealizationo In schizophrenia and mood disorders (depression, mania) all parts of the thought (thought process as well as content) are involved.o However, schizophrenia is conventionally referred as formal thought disorder.