It's always naturally there, but things like seeing it here on the net, well obviously is a trigger, that and feet pics. In real life I can't say...seeing females in general I think will make me fantasize about it, yes, but then only the ones I interact with, because those are the ones I think I have a chance with; like one I met recently who said I reminded her of a boyfriend she once had who was into some pretty kinky stuff. I don't come across that way at all in real life, but maybe she was perceptive and picked up on something, who knows. But now I'm thinking of her a lot, and I know I'll run into her again...
The other thing I thought of is, aside from pics and vids on the net which of course don't count, seeing girls' feet in real life, like in the summer when they wear flip flops, etc...that'll do it, yeah. Not now so much that it's cold out, but those sexy boots are a turn on too...do boots make me think of tickling? Sure, in a way...definitely in an f/m sense, because boots on females definitely have that dominating affect on me which I have a weakness for, same with certain shoes, like stilettoes and anything pointy...>
....also seeing exposed tummies will do it for me, which I have a weakness for...yeah I love to tickle them, and no it doesn't have to be a girl I know. That makes it better but it doesn't always have to be that, for me to get triggered!
But that's just what I see...as far as actions go....if a girl gets kinda flirty with me, which doesn't happen too often, but if she does it in a teasing sorta way....yeah, I think that will make me imagine her gettin' kinda aggressive, tying me down and tickling me, lol. I'm a 'ler too, but I think these are the sort of things that come to mind more strongly, yeah. I'm a switch but...I probably get much more excited as a 'lee...
I'm assuming "switch" means both 'ler and 'lee; that's what I picked up from being here.