Students often find it difficult to choose between the present continuous and present perfect continuous tenses. This is understandable because there is an overlap in usage and sometimes both can be used interchangeably. I wrote a few thoughts and examples for a student who asked me about this recently. Here they are:
1. “I am reading a good book.”
[I am now in the middle of it. It started in the past. It will continue into the future.]
2. “I have been reading a good book.”
[I have been doing it from the recent past till now. Unless I say anything more, I will probably continue reading it in the near future, until I reach the end.]
3. “I have been reading a good book a lot recently but now I have no time to finish it.”
[The reading took place from the past to the present but will not continue into the future]
The present perfect continuous tells you only what has happened till now, but the context often indicates that it will continue into the future, because the activity is unfinished, as in 2.
But consider this:
[<em>At lunchtime] “</em>I have been reading emails all morning.”
I am now on my lunchbreak. I am describing only what I have been doing all day until now. It may or may not continue into the future. We would need more information in this case as reading emails is not necessarily an activity which has finished or not finished.
4. “I have read a good book about gardening.”
[I have finished it, at some unspecified time in the past, but now this achievement is relevant to a current situation.]
5. "I have read many good books by that author."
[This is a repeated activity during a period of time up to the present. In this case, the period is my whole life because I haven’t defined it further.]
6. I read books.
[This is a regular activity. I may not necessarily be reading a book now.]
"Evolve"
With a verb like “evolve”, it can be used like this :
a) “Some people say that humans and primates evolved / have evolved from a common ancestor.”
[Past simple, if we consider the transition as happening at a fixed point in the past.
Present perfect, if we consider the transition as happening at an unspecified point in the past. The difference is very small in this kind of example and both tenses are equally OK.]
b) “Technology is constantly evolving.”
[We are now in the middle of a continuous process of evolution.]
c) “Automotive technology has been evolving very fast over the last few decades, but the rate of change is expected to slow down now.”
[We use the present perfect continuous to explain what has been happening from a point in the past till now.]
Hi Paula, It's good to see you.
1. If "reading a good book" mean have range period in weeks, that's make unclear, because someone can assume for himself/herself that the periode is in months, years or so.
2. "I have been reading a good book". We say that, because we are not finished read the book. If we know exacly that we finished read the book, we can say I've read the book
but i'm not sure too :-)
Good question, Laura. I think the continuous tense is better because it indicates an ongoing process which however is changing its nature from the present. The simple tense emphasises an achievement and so is often a more natural choice when that achievement is complete in the present.
In practice here, the choice of the present perfect simple would not create any real ambiguity of meaning, especially as the verb "evolve" refers to a process and not a single event.
If you say : "I am reading a good book", it can mean either,
a) It is in your hands right now
b) You are not reading it right now but around now; perhaps you started it a few weeks ago. Whenever you started it, you have not yet finished it.
If I say, "I have been reading a good book",
it never means a) It is in your hands right now.
It does mean c) You have read at least some of it, and
d) we know more about what you have been doing with your time recently (i.e. reading).
But you haven't finished the book because, in that case, you would say "I have read the book".
However, you may have decided to change your activity and stop reading the book from now on.
Good questions again!
I'm sorry, I mean Hi Laura, It's good to see you.
I am not able to answer your question, I am sure Michael will. I think you are correct (not sure!)
1. I am reading a good book: You are reading a book right now.
2. I have been reading a good book: You've read book that you've not finished yet
I wonder if:
1. I am reading a good book: If we could use this sentence to mean that this week I am reading a good book, not meaning right now but this week.
2. I have been reading a good book: If it could mean you've read it for a period of time and now it is finished. I know it is said that if you've finished the book it should be past but I wonder if P.Perfect Continuous would also be possible.
