With the present and past tenses, the progressive aspect conveys idea of limited duration; the non-progressive form does not.
When used in conjunction with the perfect aspect, the progressive aspect still conveys an idea of limited duration. The perfect aspect, with the idea of retrospection, looking back at something that continues to, or has an effect on, the present, can also (at least indirectly) convey the idea of limited duration. This means that the differences in the meanings between the non-progressive and the progressive forms of the present perfect are not alway as clear-cut as the differences in the present- and past-tense forms of the two forms.
It is worth pointing out, too, that single sentences can give only an idea of possible meanings. In real life, context will determine how a speaker views a particular situation at the moment of speaking, and may more obviously make one form more likely than the other.
1.It looks like it has been raining.
2. It looks like it has rained.
Because the progressive form is often used for duration, #1 can suggest that the rain went on for some time, leading to the wetness we see all around. in #2, there is less emphasis on the duration than on the fact that the rain has stopped. In practical terms, there is not a great deal of difference between the two in these sentences. There would be a greater difference in:
3. It has been raining since midnight.
4. It has rained since midnight.
In #3 more emphasis is placed on the fact that it is still raining.
#4 is closer to a simple statement of the fact of rain some time between midnight and the present moment.
If it is still raining at the moment of speaking, #3 is normally more likely, in my opinion.
5. She has been stealing my jewellery.
6. She has stolen my jewellery.
Because of the implication of duration conveyed by the progressive form, #5 suggests that there has been more than one act of theft over a period of time. #6 is more likely to refer to one act of theft.
7. We have been working really hard over the last few weeks.
8. We have worked really hard over the last few weeks.
#7 can stress the duration of the hard work and/or the fact that the work has not yet been completed.
#8 perhaps implies that the work has been completed.
#9. She has written many emails this morning.
#10 She has been writing many emails this morning.
#9 can suggest that the writing is completed.
#10 can stress the duration of the writing and/or the fact that the writing of emails is not finished yet.
Note that if we used a number instead of 'many', only the non-progressive form is likely.
#11. I have been spending the morning writing emails.
#12.I have spent the morning writing emails.
The difference here is similar to that between #10 and #9.
A final note: The difference between the two forms in the perfect aspect presents problems for many learners and some teacher. This is partly because many coursebooks give oversimplified explanations ("the action in the progressive form is still going on, that in the non-progressive form is not"), partly because, especially with verbs that denote an action/state that often extends over a period of time, there is sometimes little practical difference between the two forms; and partly because we often need more than one sentence to give us sufficient context to find a convincing explanation.
