For women, the vagus nerve is sometimes connected to orgasm. Depending upon the woman and depending upon the stimulation.
Tickling...for the ler...is a fairly playful way to explore that. For the lee...it just depends.
With my current friend, I spent a couple of weeks being gentle with it and getting the laugh. I went a little "deeper" with the finger and pressure later. She still laughed. Louder. In fact, she leaned into my ear and laughed. (I love that, by the way). But you should have seen her face when I really stimulated her belly button more firmly. She was still laughing...but she was a little shocked and surprised by the stimulation. She blushed too. I think there might be a little more going on there. I might try to find out more. Maybe even tonight.