When you are tickled, your laughter is the reaction that occurred because that ticklish feeling sends us into a state of panic. You most likely weren't expecting that person to sneak up behind you and tickle your sides, were you? This was probably a defense mechanism that developed in our cave-men ancestors to detect predators. When you try to tickle yourself you are in complete control of the situation, there is no need to get tense and therefore there is no reaction. The part of the brain that cancels out stimuli it is expecting is called the cerebellum. The cauliflower-like mass can be found at the back, under the brain. The cerebellum is known to basically be the party planner, it coordinates movement control in relation to sensory signals received in other areas of your brain. It is possible to tickle yourself though!!! You would have to fool your cerebellum. Studies have shown that with as little of a 200-millisecond delay between you moving your hand and the tickling, you would react. However there is only one way to do this- by remote control. Science has been able to design a robot that allows people to tickle themselves. To use the machine you would have to lie on your back with your eyes closed. The robot, located near you, would have a piece of soft foam attached to a plastic rod which you would control by joystick. 操纵杆You would maneuver the remote control and after a short delay, would respond. This takes advantage of the delay in the cerebellum.   sneak up: 悄悄出现，突然接近       cerebellum: 小脑 cauliflower: 花椰菜           joystick: 操纵杆