Rain

Nothing, really.

Really? Then what about these? Do you think these are both natural? If not, why not?

She never saw it, but she felt a mosquito bite her.

She never saw it, but she felt a mosquito biting her.

Yes. The action/experience is relatively brief: either form will serve.

Right. The experience of being bitten is brief. And she never saw it.

Then I wondered if the experience was so vivid as to be described as 'biting'.

Either form will serve.

Then let me ask this way. Would you come up with an example where one will serve better than the other?

She saw him running around the block = She saw at least a portion of that accomplishment.

She saw him run around the block - She saw the complete accomplishment.

Mister MicawberShe saw him running around the block = She saw at least a portion of that accomplishment.
She saw him run around the block - She saw the complete accomplishment.

Yes, that's what most of the grammar books I have say. And then recently I came across the example I had given above (I came aross the 'just watiching it rain' example).

Th

I thought maybe it had something to do with vividness -- When both forms can be used synonymously in the situation, that certainly comes into play when the choice is made.

I see. Thanks, MM!