David Dobbs writes: We don’t know what led Holmes to do this, whether he was, to use David Eagleman’s distinction, psychotic or psychopathic or something else altogether. But unlike Anthony Lane and many other commenters, I don’t think we can give the movies a free ride here by saying they had nothing to do with it and just provided a stage. They gave this actor his lines and stage directions.

I’m not saying the movies made Holmes crazy or psychopathic or some such. But the movies are a enormous, constant, heavily influential part of an American culture that fetishizes violence and glamorizes, to the point of ten-year wars, a militarized, let-it-rain approach to conflict resolution. And culture shapes the expression of mental dysfunction — just as it does other traits. This is why, say, relatively ‘simple’ schizophrenia — not the paranoid sort — takes very different forms in Western and some Eastern cultures. On an even simpler level, this is why competitive athleticism is more likely to express itself as football (the real kind) in Britain but as basketball in the U.S. Culture shapes the expression of behavioral traits. The traits don’t rise inherent as an urge to play basketball or a plan to shoot up a Batman movie. A long conversation between the trait and the surrounding culture shape those expressions. Culture gives the impulse form and direction.