This wilful cognitive dissonance was parodied in one of SNL’s greatest skits. Norm Macdonald is the leader of the Cobras; Robert Downey Jr and Will Ferrell play gang members.

Downey and Ferrell: What?

Norm: How’d you come up with a song so fast?

Downey: I don’t know, it just- just came to me. What do I-

Norm: Just came to you? What- what, it was perfect. It was like you rehearsed it, or something.

Downey: Aww… thank you.

Norm: Ok look, here’s what we’re gonna do. You go over to-

Ferrell: Hey, hey, hey, hey…

Norm: What?

Ferrell: Did you really like it?

Norm: What?

Ferrell: The song.

Norm: Did I really like it? Yeah yeah, I liked it. Hey- hey, I like another song too. You know- you know this one, it’s called, ah, “While you were singing, I got stabbed in the head by a Puerto Rican!”

So why did West Side Story work better on stage than on a TV screen? I’m sure the collusion of the audience is part of the answer. In a large group, we tend to be swept along by the prevailing mood. That’s why TV comedies add laugh tracks to simulate the experience of watching in a group. It really only works for comedy. They don’t add weep tracks to tragedies (although some scores come close).

But to me, the most interesting question is, why do we care about these characters? We don’t know them. We don’t share their environment or their concerns. (Has anyone reading this been a street hood trying to face off a rival gang or a Puerto Rican immigrant girl in love with her brother’s killer?) More than that: we know these characters are fictitious. They never existed. So why do we care?

I think the answer lies in our neurobiology, which itself lies at the end of a long chain of evolution as social primates. But this still doesn’t answer why some stories can make us care about fictitious characters breaking into ridiculous dances as they fight to the death (as in West Side Story) while other stories utterly fail to engage us, even if they are (intended to be) realistic about emotionally powerful topics (as in Crash or Taken).