paruha wrote:See it happen:
We saw Trevor plant the tree. (He planted the tree. We saw him do the whole job.)
I watched NIck light a cigarette.
We noticed a young an sit down and order a meal.
See it happening:
We saw Trevor plating the tree. (He was planting the tree. We saw him in the middle of the job.)
I watched Nick smoking a cigarette.
We noticed a young man sitting at the table eating a meal.
When we talk about short action, it often does not matter which structure we use.
See it happen: We can use this structure with the following verbs: feel hear, listen to, notice, see, watch
See it happening: We can use this structure with the following verbs: feel, find, hear, listen to, notice, see, smell, watch
(I skipped some of the examples, but I think they aren't that important)
Thanks for posting that, paruha. It's helpful. I also queried some linguists, and their explanation, though slightly different, is in line with what your grammar says.
As your grammar suggests, the difference becomes more apparent if you take a long-action verb like "build."
1. I saw them build a house.
2. I saw them building a house.
What the linguists pointed out was that #1 means that you saw them finish while #2 means that you saw them while they were doing it - they might not have finished.
To make this very clear, suppose you are taking a walk and you walk past a building site. You see your neighbors building a house. You go back home and tell your mother: #2 "I saw them building a house" not #1 "I saw them build a house." #1 would mean that it's over, finished, so you would need to use #2.
Or another example:
#1 I saw Joe walk across the street.
#2 I saw Joe walking across the street.
At the moment that Joe is half way across the street, you pass by in your car. You don't actually see him get to the other side of the street. In that case, you have to say "I saw Joe walking across the street."
It was really difficult for me to see this difference in the beginning for some reason.
United States (United States) 
The only idea I have is that because one form will always be shorter than the other (syllable-wise), a speaker may opt for one over the other to modulate the rythm of his expression.
United Kingdom (United Kingdom) 
Bulgaria (България) 
Please do! Maybe Paruha's Oxford "grammar" will persuade me...) It seems more likely the distinction will come from stress put on certain words, and of course, context. 
)
France (France) 
to post.
