Behavioral Contrast: Keeping up with the Jones' is a tough thing to do, and is motivated by, well, the Jones'. This behavioral contrast represents the fact that the goodness of any behavior is not measured by absolute but by relative measures. That is, it hurts when you see other people having bigger cars, fancier houses, and neater lawns than you. So, to alleviate all that hurt, we try to outdo them in the materialism department, and thereby shift to them our pain, which is temporary anyways since the pain returns with our credit card bill. Behavioral contrast is the reason we are motivated to accumulate more and more stuff, when what we should be doing is build higher fences. from Dr. Mezmer’s World of Bad Psychology, found on an internet near you!
I'd appreciate it if you gave the clinical definition with source, then dumb it down, then dumb it down again until you can fit the whole idea into ten words.