Steven Pinker on the decline of violence

I'm developing a teenage-girl-esq obsession with the cognitive psychologist and popular science writer Steven Pinker (he's so intellectually dreamy!). He's got quite a talent for finding some sense in the mysteries of human behaviour and communicating these insights in a super accessible way.

In the following video (that I was delighted to discover this morning) he gives a really interesting 15 minute talk on human violence. He argues that contrary to popular belief, violence is in decline. He then looks at some of plausible theories of why this might be.


http://www.ted.com/talks/view/id/163

I'm particularly intrigued by one of the theories that he briefly addressed: the notion that modern humans enjoy their own lives more (thanks to the comforts of modern living), they value their own lives more, and this leads them to place greater value on the lives of others, making them less violent.

How would you test that? Would you expect to see a correlation between subjective wellbeing and humanitarian attitudes? Or between self-esteem and humanitarian attitudes?