Why do we find it hard to torture robots?

Meet DAR-1. He might not look like much, but robots like him are showing startling new ways that humans can interact with machines

In still pictures, DAR-1 (pronounced 'Darwin') doesn't look like the kind of robot that might encourage empathy.

The machine's six spindly legs lend it an uncanny arachnoid appearance, and with no case for modesty's sake, the exposed circuitry doesn't hide its electrical heart.