Master Chief, thank you so much for the vote of confidence...you made me blush...:redface:
Anyhoo, I don't have a definite answer, but I do have a solid theory based on my anatomical/tickling knowledge...
Men have thicker vocal chords to begin with, which allows for a deeper, more "masculine" tone when speaking and laughing in a normal manner. Even a good, deep, belly laugh at a funny joke remains in the normal register because your respirations are not stressed. When tickled, and put under stress, the force with which the air is moving across your vocal chords is higher. This, paired with the tension in most of your muscles in your body in response to the tickling, causes the vocal chords to vibrate at a different frequency, allowing for a higher pitched laugh to escape.
That's just my theory...but it's something that should be studied more thoroughly...I would be MORE than happy to become head researcher if I could get some willing subjects...😀