Under the sentences I don't know how come the perfect progressive tense is used-with FOR, past perfect is sufficient.
Can you give me why?
By experimenting in the laboratory, Lorenz found that young geese had an innate tendency to follow a large, moving object if they encountered it soon after hatching. If the object was removed before they had been following it for ten minutes, then the geese would just follow the next large, moving object that they came across.
Can you give me why?
By experimenting in the laboratory, Lorenz found that young geese had an innate tendency to follow a large, moving object if they encountered it soon after hatching. If the object was removed before they had been following it for ten minutes, then the geese would just follow the next large, moving object that they came across.
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Comments
You could certainly say 'before they had followed it for ten minutes', and in fact I prefer that.
I assume the writer wanted to stress the duration, ie that ten minutes was a long time in those circumstances.
That's why my wife says to me,
'I've been waiting for you for an hour'
instead of
'I've waited for you for an hour'.
Clive
I have been following this car for ten minutes.
I agree, we're hard pressed to find a difference in these two meanings.
I guess it's just the nature of the progressive tenses.
They focus on the continuous nature of the action. (That's why we sometimes call them "continuous.")
There's also an implication that the action will continue into the future, while the perfect tenses might give the impression that the action is complete.
Thanks, Avangi.
"For" is a preposition that works with durations and continuities (at least, in the context that you gave as an example). While the purpose of introducing the Perfect Progressive tenses into English language was to reflect exactly durations and continuities. Past Perfect (neither two other perfect tenses) NEVER work with durations since they are to reflect the COMPLETENESS of action, which is known as 'perfect aspect" in most world's languages. The fact that you may have encountered millions of cases when Past Perfect was used to reflect the duration, doesn't mean anything. It's mangled English.
If, as you say, one has encountered millions of examples of X, then objecting to the use of X on the grounds of a lack of systematicity becomes moot.
Not all grammarians agree that the perfect tenses "are to reflect the COMPLETENESS of action."
He had looked at it for hours before it finally made sense to him.
CJ
He had worked there for years before he finally got a raise.
I had sung in that choir for three months before I realized that the choir director was my long-lost brother.
The correctly formed above sentence should look "He had been looking for hours before...". He had been working for years before he finally got a raise.
I had been singing in that choir for three months...
The problem lies in your readiness to substitute Perfect Continuous tenses (which work with durations and continuities) with Perfect tenses. That is the biggest problem of English grammar. An unovercomeable one. You can't equal a resultless process to a completed action with a result (i.e., can't equal imperfect aspect to perfect one). "He had worked there before he got a raise" means that he was fired BEFORE he got a raise. "He had been working before he got a raise" means he went on working after the raise.
Please, note I'm not arguing the overwhelmingness of the usage of Perfect tenses in the continuous contexts. Sorry to repeat it, it's mangled English. I can show you how so called "Present Perfect" tense had been getting contaminated and misinterpreted step by step (there are at least four such steps/stages), but understandably not on the forum. It's a 2-hour lecture.
If the English-language society at a certain stage conceded the erasure of the border between diametrical tenses (as diametrical as perfect and imperfect aspects are) it shouldn't get beguiled by the idea of boasting of systemic grammar ever since.