Well the moderators previewed the joke I was thinking of posting and decided it was - ahem - unsuitable. So here is a clean one:
The Psychology Student A very shy young man goes into a pub on Valentine's Day night. His eye falls on an extremely beautiful young woman sitting alone at the bar. Since it's Valentine's and she is by herself, he decides to summon up his courage. He walks up to her and asks: "May I buy you a drink?" To his astonishment she shouts at the top of her lungs, "No, I won't have sex with you !" Everyone in the pub is staring at him and he is so embarrassed and red-faced he slinks back to his seat in a dark corner of the pub. After a few minutes, the young woman walks over to him and smiles at him. She says, "I'm very sorry for doing that to you. You see, I'm a graduate student in psychology and I'm studying how people respond to embarrassing situations." The guy nods thoughtfully, smiles at her and then shouts at the top of his lungs, "What do you mean you'll do it for $300?!"
Slow Travel Talk 
