If you’ve ever flown in economy class on a plane, you probably had to walk through the first class cabin to get to your seat. Maybe you noticed the extra leg room. The freshly-poured champagne. Maybe you were annoyed, or envious. Social psychologist Keith Payne says we tend to compare ourselves with those who have more than us, but rarely with those who have less. This week, we explore the psychology of income inequality, and how perceptions of our own wealth shape our lives.