(I have to use large fonts because my eyesight has become worse. Sorry about this.)
If you should find the questions in this forum about Simple Present and Simple Past are only biases or insignificant, try the Present Perfect here.
In my youth, as I in avid eagerness asked about Present Perfect tense in letters by air to some places overseas, they posted to me a free issue of ELT Journal, which was published by Oxford University Press in association with The British Council. In the Journal a P.S. Tregidgo published his rather startling comment: "How far have we got with the present perfect? " He expressed his doubles and dissatisfactions over both conventional and advanced methods to explain the tense. And he finally concluded: “Meanwhile, one thing seems to me to be pretty clear. Whatever the grammarians may say about it, the problem of the English present perfect remains very much alive and kicking!” I didn't subscribe the Journal. I have only one copy of it, the one they sent to me free of charge.
Please understand the comment could not be published without careful considerations by the experienced editors. To some, the conclusion was obvious. As they really could not explain the tense, they had better admit openly. This relieves the merciless pressure added on both teachers and students. Most of all, however, they didn't want to lie and sell falsehood to innocent people. It is immoral for an ignorant teacher to cheat students that they should understand Present Perfect. As a matter of moral, tell them the fact.
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However, many teachers and students still don't believe the difficulty. They know part of Present Perfect and pretend they have got it under full control.
In the following web page, there is a comment by Sarn Rich that can be reckoned as the updated version of Tregidgo's article:
http://www.developingteachers.com/artic ... 1_sarn.htm
Interesting, the criticism against Present Perfect is placed within a website designed for developing teachers. You may wonder Why? To me it is obvious. Rich wants to do something good, as same as Tregidgo did. The insightful comment must be there reminding developing teachers that the tense is a torture, advising them not to push yourself too hard. It is immoral to claim you understand Present Perfect when you actually don't, and tell students to understand it.
Ironically, the author thought at first he had mastered the tense and owned the knowledge enough to teach developing teachers:
Budapest, 1992. I thought the lesson was fine, until Agnes threw down her pens, wailing, 'I'll never understand the present perfect!'
Wailing! How many teachers and students have wailed at the tense? The real hindrance is, however, many confused grammar writers, now teachers, still claim that their explanations are clear and good ones. Students have no reasons to wail, they think. The erudite author is now standing up and kicking at the most popular or advanced theories of our time, which claim they understand Present Perfect. He is so paranoid about the tense that he could not trust anything of it. He ended the article and wrote:
At last, the author repeated in Appendix:
Timelines can be helpful, but may be dangerous if their function as analogies is forgotten (Lewis 1984:170-176). They may also be very different and so potentially confusing.
If you should find Lewis' "The English Verb" may help the author, please contact him. But you shall take a look at first whether the author did study the book or not. Of course, a man as clever as you must have more understanding than the unqualified author, so I guess you had better write to him directly. Don't just tell him to read it. Rich did read the book but still not understand the tense. Do you get the point?
Several years ago I received a call from a friend. She was hoping for a place on a TEFL Certificate course, and she had a problem. 'Help me' she said. 'I can't get my head round the present perfect.' Easy, I thought. I was wrong.......
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The main point of both Tregidgo's article and Rich's comment seems to be only Present Perfect, but in the contents there are really two tenses intertwined: Simple Past and Present Perfect. If Present Perfect is confusing, it is because it is confused with Simple Past. For the past few decades, I have not met a person who could tell the difference between them.
One unpardonable point is that after we have spent energy to separate Simple Past from Present Perfect, in reported speech they have to become one again:
Ex: They reported that they had seen the tiger.
== Past Perfect can be derived from either Simple Past or Present Perfect.
Now the two tenses have to have a difference not so small that students can see clear the difference, and not so big so that they have a reason to combine. Happy now?
Some books have gone too far. Pretending that they can explain the two tense, some grammar writers cleverly claim a falsehood that Present Perfect doesn't stay with past time expressions, and then from their books they hide away any past time expression that can stay with it: in the past, before, over the past four years, etc.
Now the falsehood and concealment are a must, for every single grammar book, or website.
For the past few decades, I have been looking for the first book that may talk about the Past Family, such as in the past, in the past year, in the past two months, during the past three decades, on the past few days, over the past four weeks, for the past few years, within the past four centuries, at the past few meetings, etc. Their pattern is "in the past xx years". They contain the adjective past and thus refer to the past. I still cannot find the book.
The Past Family are difficult to explain because they refer to past but stay with Present Perfect:
Ex: They have worked here for the past three years.
These time adverbials violate the false invention that Present Perfect doesn't stay with past time expressions. They therefore are buried alive. The evidence is invisible: you cannot find any of them in any grammar book. However, just because you cannot find any of these time adverbials explained in an grammar book, it is guilty of concealing the difficulty and selling falsehood to young students.
(Many naive persons claim there is no such concealment, because it is simply invisible.)
Unfortunately, any teacher who, without prior notification of the reality from grammar writers, has preached the falsehood to students, has to defend it against the truth, if the truth is exposed. This is the wisdom of grammar writers who has planned the falsehood: "As now you have committed the crime with us, go along with us, or we all lose our jobs. Morality doesn't make money these days."
Take Collins Cobuild English Grammar (Collins Birmingham University International Language Database, 1990) for example. It claims "Helping learners with real English". The Editorial Team consisted of a dozen of learners. They found real examples from nearly a thousand of periodicals and publications. Though I seldom buy grammar books, I bought one copy of it because I was attracted by its insightful analysis and vast examples. Everywhere they could spot exceptional but useful constructions. Of course, they could do it because they had huge manpower and database. However, as for English tense, they don't found any example of the Past Family. Do you believe these examples were so rare that every member of the Editorial Team could not meet any one? I don't think so. Actually, the luck by which they missed all the examples of the Past Family helped support the familiar rule they wanted to deliver to you:
Having made such warning, they had to be wise enough not to pick up examples like this:
WARNING: 5.34 You cannot use adjuncts which place the action at a definite time in the past with the Present Perfect.
Ex: They have worked here for the past three years.
These examples unfortunately place the action at a definite past time in the past with the Present Perfect. They were therefore left alone in the database, frozen. I guess they would have held a meeting to discuss whether they should give these real examples to reader or not. The conclusion was obvious.
If you can explain that for the past three years doesn't relate "a definite past time in the past", don't tell me. Please tell the Editorial Team so that they can resurrect these valuable real examples.
Allow me to remind you this: Not just Collins Cobuild English Grammar, all grammar books have missed the examples for the Past Family. Fellow teachers, would you explain this?
On different occasions I have discussed with some webmasters over the web, who own a website for English. We discussed about the examples of the Past Family. I then suggested, "if you believe in your own explanation, would you talk about these examples now in your website?"
They usually answered "I think about it", or "certainly we will". Now readers please be informed: they won't. You still cannot find a website talking about these examples.
You may try yourself to report some examples illustrating the Past Family to some websites about English. Tell them you find what they haven't found, and recommend them to put the valuable examples in their websites. You may want to see what happens. No concealment, you say?
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Please be reminded that, both Tregidgo and Rich didn't talk about the examples I have pointed out:
Ex: They have worked here for the past three years.
Therefore, even if my information is infinitesimal and not valuable enough, Present Perfect is still hard to handle.
Xui
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This message is rather long and I didn't review much. I understand there are many mistakes. I strongly remind some filthy linguists not to review it. No response will be provided to you from me.
), it seems another conspiracy theory has been exposed for what it is - the rantings of a crazed loner. 
