Imagine you are with your family and you are play with your child by quickly tapping their back. Now if the child has seen you moving should they say to you:
I have seen you or I saw you
I feel, maybe from my watching experience, saw is the right response but then, does not this scenario better fit the present perfect because what is involved here is only the person who taps and the recent action, not the time (both parties know the time).
P.S. Now I could think of the game hide and seek as another example of this issue
Best Answer
It's I saw you or I see you (if playing hide-and-seek or peek-a-boo).
When you say I have seen you, what you're really saying is I've seen you several times at [possibly] various places. Or that you've just seen them around somewhere or sometime. There is no indication of a beginning and end of the event; or if there is, you're unaware of the details.
Present perfect is used for events that began at an unspecified point in the past. You may or may not know whether it's still happening or not. It usually has relevance to the present,
As for I saw you, that's the simple past; and as you've suggested, it's correct.
The simple past is used for events that have only occurred once, were one-time events with a definite ending, and/or are not happening again (i.e I mean that specific event).
So, to return to the hide-and-seek reference, you use the simple past saw because you only saw them ocne. And once you saw them, that event was over.
Where it gets tricky is that I saw you technically means:
If they're hiding, and you can see them, then it's obviously I can see you.
I've seen you hiding, means you've seen them hiding previously, possibly many times. It also is something that you would say if your child asked you to play hide and seek; in turn, you'd say:
The best rule of thumb that I can think of would be that if it only occurred once, you have no reason to expect it will return, and you know exactly when it happened, then it's the preterite.
Otherwise, you'd use the present perfect.