Interesting .I have read somewhere that what is at work behind kindness is the "empathy neurons" which seem to be experiencing suffereing in others as though it is theirs. I mean whenever a kind man sees suffering ,something in him produces a similar kind of suffering in sympathy or rather in "empathy".Neurologists say that altruism is a natural born tendency ,not a cultivated one. The very word "kindness" implies identification with  persons of the same "kind "