desensitisation is what occurs when extensive exposure to a stimulus causes a person to stop reacting to it. it's useful for overcoming phobias. it's also useful for getting your heartrate to remain constant when you are presented with images of bloodied people bits, thereby messing up the experiment you are participating in. apparently, heartrate is supposed to skyrocket when you watch people being skinned. and apparently, if you joke enough about dead babies and playing with human insides, they stop eliciting a physiological reaction. mind over matter, mates.