Researchers believe that laughter caused by tickling is part of the defense mechanism by which the "victim" announces his surrender. During the study, the volunteers underwent an MRI scan of the brain to determine the similarity of laughter from tickling with laughter, which is a reaction to a joke or a funny situation. As it turned out, both tickling and laughing tend to activate the part of the brain that controls facial movements, as well as vocal and emotional responses. However, tickling also activates the hypothalamus, which controls body temperature, hunger, fatigue, and sexual behavior, as well as instinctive defensive reactions. Therefore, scientists believe that some people start laughing just from the threat of tickling.