Good article overall to stimulate further reading. The dopamine hypothesis is actually more complex than presented. Schizophrenia is characterized by positive symptoms (such as hallucinations and delusions), negative symptoms (like withdrawal), and cognitive deficits. The dopamine hypothesis is that both too much and too little dopamine is causing problems. There's too much dopamine in subcortical regions of the brain and that may be the cause of positive symptoms. There may be too little dopamine in cortical regions and that may be associated with negative symptoms. As the article rightly points out, there's lots of other players besides dopamine.