I've offered to teach Steve V how to juggle on more than one occasion, but he has never taken me up on it. Hmph.
I don't know if learning to juggle increased grey matter in my brain, or if that grey matter mattered to anything other than my juggling ability. But I know that juggling deeply changed my perception of myself.
Before I learned to juggle, I thought that I couldn't juggle. I really believed it. I've always been bad at sports, particularly ones involving catching balls. A misspent childhood, reading too many books, I guess. I had tried to learn to juggle, and had failed.
In college, a friend taught me how to juggle. Actually, we taught each other: I taught him how to program computers, and he taught me how dexterity, and in the process, I learned how to juggle.
It was a struggle--I took longer than most people to learn how to juggle. But the elation I felt when I learned! More importantly, I had a huge realization: what other things do I think I can't do, but I really can do them, if I just put in the time and effort? This realization has changed me.
In addition, I met my wife in the juggling club. Extra bonus!