Does anyone enjoy being tickled? It's a frustration that we can't wrap our heads around. However, it's always in the control of someone else's hands. If you haven't already realized, it's typically impossible to tickle yourself... did you just try it? A lab study in Berlin validated the reasons behind this.
Researchers at Humbolt University in Berlin experimented in a lab involving two subjects as controlled variables. Subject 1 sat in a chair with their arms up and feet out. Hiding behind Subject 1 was Subject 2, waiting to commence the tickle attack. To capture the responses, Subject 1 had a GoPro on his face, body, and feet and a microphone nearby. Subject 1 couldn't help but break into a hysterical laughing fit. Unless the participant involved was not ticklish, this reaction was a given. However, Michael Brecht, the group's lead researcher, justified the mysterious reaction using brain and behavior research. In this case, laughter was investigated further.
Cognitive neuroscientist, Konstantina Kilteni, noted, "if you read the ancient Greeks, Aristotle was wondering about ticklishness." So, it's safe to say the mystery of tickling has been around for a while - and we're about to get to the bottom of it. It's important first to establish that we do not know why some body parts and people are more ticklish than others. The correlation between a human response and the initial tickle is too hard to measure. Hence, the microphone and GoPro were used in the experiment to determine the duration between reactions. However, Brecht believes the reaction is "a form of social signaling in the context of play fighting," relating back to children's play. While this is considered an appropriate action during childhood, the researchers made sure the participants were comfortable with it, yet they still reacted as if it was a surprise. The main tickle spots were the neck, armpit, foot, head, and "lateral trunk." The first observation: "a person's facial expressions and breathing changed about 300 milliseconds into a tickle," and at about 500 milliseconds, there was a voice reaction of laughing after 70% of touches. However, when the ticklers tickled themselves in a similar spot simultaneously with another person being tickled, they found the responses were less intense. Data showed "the ticklee giggling dropped by 25% and was delayed to almost 700 milliseconds when self-tickling the same side." The fundamental answer is that the brain encounters a "prediction error." When the brain knows we are about to tickle, it doesn't listen. Like the nervous system, the brain's sensory activity activates before the surprise tickle attack, preparing our bodies for a reaction.
While every personality and brain is wired differently, there are key sensory signals which produce the same response activity. That being said, playfulness encourages future studies. Until then, stay tuned.