As any parent knows, tickling your small child gets you a huge positive reaction -- uproarious laughter, huge smiles, and the like. Likewise with raspberries (pressing your face in the baby's stomach and going "Phhht," as best I can transliterate it).
On the other hand, tickling an adult will also get you uproarious laughter, but the adult will generally not like it. Laughter and smiles are usually a sign of pleasure, but not in this instance. So this makes me wonder: Should we not do it to children (say, from a few months old to a few years old), either? Is there some reason to think small children really do like it even though older children and adults don't?
I assume that if we conclude children don't like it, we shouldn't do it, since tickling and raspberries don't fall in the immunizations/medicine/making-them-clean-up-their-rooms category of "we do it because it's good for them, regardless of whether they enjoy it." Or is there some conceptual difficulty with even asking "does a one-year-old like it, despite his laughing and smiling?"