What are the positive and negative symptoms of schizophrenia?

Positive symptoms are experiences added to normal functioning: hallucinations, most commonly auditory voices; delusions, which are false beliefs held despite contradictory evidence; disorganized thinking and speech; and disorganized or abnormal motor behavior. Negative symptoms are reductions in normal functioning: flat affect or diminished emotional expression, avolition or lack of motivation, alogia or reduced speech output, anhedonia or inability to experience pleasure, and social withdrawal.