There brains are too small to have any kind of complex emotion. You are dealing with instincts when it comes to snakes. They get frightened, they get hungry, they get thirsty, they get horny, and they relax. If any of these instincts are compromised, it can stress them. That's about it. Of course I don't have "scientific proof." Maybe I should pull the "common sense" card like you did. when I finish my major in Biology after I get my A.A.S. in Electron Microscopy this spring, maybe i'll process some brain tissue from some of these non thriving mutant melancholy spiders and make a conclusion to my hyphothesis. I can tell you this though. My guess is a heck of a lot more educated than yours.