Watching a movie, I've just heard of this lines:
A: "I'm just looking for Barbie. Is he around?"
B: "I haven't seen him."
I've always been confused about present perfect and simple past. So why did B say so, not "I didn't see him." What's the difference?
The dialogue appears to be from the first episode of Under the Dome and "Barbie" is the nickname for a male character named Dale 'Barbie' Barbara.
I haven't seen him
means, essentially, I have not seen him recently.
I didn't see him
means, I did not see him at some particular time.
When the "particular time" is recently, the two can be used almost interchangeably:
"Have you seen Bob around?"
"No, I haven't seen him.""Did you see Bob just walk by here?"
"No, I didn't see him."
Other times, though, there are clearer dividing lines between when to use didn't see instead of haven't seen:
"Have you seen Mr. Hernandez go into Mrs. Olson's house?"
"Yes, I have seen that many times.""On the night of the murder, did you see Mr. Hernandez go into Mrs. Olson's house?"
"Yes, I did see that."
The first question refers to a more open-ended span of time, while the second refers to a very specific time segment.
In this context, did is past and this means that some time in past, the answerer has not seen Barbie.
Using have extends the time from past into the present. I haven't seen... here means till the time the sentence is spoken, the answerer has not seen Barbie.
