The present perfect continuous form is often confused with the present perfect. Indeed, there are many instances in which the present perfect continuous can be used as well as the present perfect. For example:
I've worked here for twenty years. OR I've been working here for twenty years.
I've played tennis for twelve years. OR I've been playing tennis for twelve years.
The main emphasis in the present perfect continuous is on expressing how long the current activity has been happening. It's best to stress that the present perfect continuous form is used for shorter periods of time to express how long that particular action has been taking place.
I've been writing for thirty minutes.
She's been studying since two o'clock.
In this manner, you'll help students understand that the present perfect continuous is used to express the length of a current action. Compare this to cumulative length for which we tend to use the present perfect, although the present perfect continuous can be used.
Introducing the Present Perfect Continuous
Start by Speaking about the Length of Current Actions
Introduce the present perfect continuous by asking students how long they've been studying in the current class on that day. Extend this to other activities. It's a good idea to use a magazine with photos and ask questions about how long the person in the photo has been doing a particular activity.
Length of Current Activity
Here's an interesting photo. What's the person doing? How long has the person been doing XYZ?
What about this one? He looks like he's getting ready for a party. I wonder if you can tell me how long he's been getting ready for the party.
Result of Activity
Another important use of the present perfect continuous is to explain what has been happening that has caused a present result. Stating results and asking questions are effective in teaching this use of the form.
His hands are dirty! What has he been doing?
You're all wet! What have you been doing?
He's tired. Has he been studying for a long time?
Practicing the Present Perfect Continuous
Explaining the Present Perfect Continuous on the Board
Use a timeline to illustrate the two principal uses of the present perfect continuous. With such a long string of helping verbs, the present perfect continuous can be a bit confusing. Make sure that students understand the construction by providing a structural chart like the one below:
Subject + have + been + verb(ing) + objects
He has been working for three hours.
We haven't been studying for long.
Repeat for the negative and interrogative forms as well. Make sure students understand that the verb 'have' is conjugated. Point out that questions are formed with "How long ..." for length of activity, and "What have you ..." for explanations of current results.
How long have you been sitting there?.
What have you been eating?
It's a good idea to compare and contrast both the present perfect and present perfect continuous when first teaching this tense. At this point in their studies, students should be able to handle working with two related tenses. Use lessons that focus on the differences to help them distinguish usage. Quizzes testing present perfect or perfect continuous use also help students become familiar with the two tenses. Present perfect and continuous dialogues can also help with practicing the differences. Also make sure to review non-continuous or stative verbs with students.
Challenges with the Present Perfect Continuous
The main challenge students will face with the present perfect continuous is understanding that this form is used to focus on shorter lengths of time. I find it's a good idea to use a common verb such as 'teach' to illustrate the difference. For example:
I've taught English for many years. Today, I've been teaching for two hours.
Finally, students may still have difficulties with the use of 'for' and 'since' as time expressions with this tense.