I was also reminded of an advertisement for a television brand which used to run a long time ago – the tagline was “Neighbor’s envy, owner’s pride”. That gives me another conclusion – one is not proud of one’s accomplishments/possessions unless there’s someone envious of those things!
So to summarize, it seems to me that humans are not programmed to be happy until they see someone in, what they consider, a poorer state than them!
Why is that? Does a bigger brain has this side-effect? But then I wonder what makes an elephant happy! Any thoughts?