1-The children are tired now. They have been playing in the garden.
2-Are you ok? You look as if you have been crying.
I question why we use present perfect continuous instead of present perfect simple in these two examples. As I see the actions have finished, I thought I should use present perfect simple. Could you guide me through the answer?
One of the main functions of present perfect progressive is to talk about a recently finished event that has visible results in the present.
In the case of your examples, this applies because (1) the children are visibly tired, and (2) your eyes are bloodshot and watery.
Let's look at the meaning of the sentences without the continuous aspect:
1-The children are tired now. They have played in the garden.
This means the children played in the garden at some time, not necessarily recently, so there's no connection implied between being having played in the garden and being tired now. Someone might get the connection because of context, but it sounds odd. The nuance that it's recent is lost.
2-Are you ok? You look as if you have cried.
Again, the recent aspect is lost, and "you have cried" suggests "at some point in your life", not necessarily recently enough to have made your eyes bloodshot right now.
Yes,the present perfect continuous tense is absolutely ok in those two examples. This tense can describe an action that started in the past and has just stopped, but it has the present results. In the 1st example, the children started playing in some past time and has just stopped playing, and the result (i.e., he is tired) is still present. So, the present perfect continuous tense has been used here. Similarly, in the 2nd example, you started crying in some past time and you have just stopped crying but the result is still present; therefore, you look so. So, the present perfect continuous tense has been used here.
The present perfect continuous tense- The action can end just before the present.
'They have been playing in the garden.' The action has ended just before the present. They are not playing now. They have just finished playing.
You look as if you have been crying. You are not crying now. You have already stopped crying. The action has just ended.
[It smells as if someone has been smoking in here.]
