Sheldon: You just lied to Penny.
Leonard: Yes, I did.
Sheldon: And you did it so casually. No rapid breathing, no increase in perspiration.
Sheldon: So, lack of physiological response while lying is a characteristic of a violent sociopath.
Leonard: Sheldon, are you worried about your safety?
Sheldon: No. I imagine if you were going to kill me, you'd have done it a long time ago.