The number one benefit of investigating into the hindrances is to see very clearly that you've got Dukkha, to see very clearly you've got fire. That's number one thing, the most important thing. Because if you don't see you've got Dukkha, then you're not going to care about letting it go. You're not going to care about where it came from, you're not going to care about whether it comes back again in the future. If you don't see the Dukkha, you're not going to care more about the causes of the hindrances, you're just going to sit there watching the hindrances come and go, come and go, come and go. And you can get very interested in watching them come and go, but you won't stop them coming again in the future unless you understand that they're creating Dukkha. That's the number one, most important thing about investigating into the hindrances.
After you understand it's Dukkha, we would like to know where it comes from, how it goes away, we would like to know how it will not come again in the future. When we understand how it will not come again in the future, then we can lessen the causes for their arising. So investigating the hindrances is not just for attaining better concentration, it's for actually developing wisdom in order to end Dukkha. Now, as we're able to let go more and more of hindrances, concentration comes automatically. It will just automatically arise better and better as we let go of everything that's blocking it. This is important to understand.
In Vipassana meditation we focus on getting wisdom that will help to let go of the hindrances and concentration comes later. In some other techniques called Samata meditation people focus on getting concentrated by suppressing the hindrances. That's all it does, it only suppress them, it doesn't get rid of them at all. If a person does Samata within Buddhist practice, they must also do Vipassana so they learn how to let go of their Dukkha. But if a person does Vipassana practice, they do not have to practice Samata also. The concentration will come automatically the more we let go of the hindrances.
How does it help understanding Dukkha and its causes? Well, I think that's more or less covered - we see the fire and we start to understand it. Then we have to investigate. Looking just at the hindrances, like investigating the hindrances. But just looking at it, only looking, that doesn't give us the wisdom. So the investigation also includes reflecting upon, which is why we also teach the reflection meditation.
Say you got really angry this morning about something and it sent you in a spin for a couple of hours. This afternoon, sit down and reflect on the Dukkha that you created. Try to look at it, try to look at it each way; this is part of the Dukkha reflection. You take an example from your life and you investigate it, investigate it. How did it happen? How did it go away (if it did already)? How does it not come again in the future? What are the causes, what are the causes?
A clear case of a simple lack of mindfulness - you sit in the hall, you're meditating and a truck comes up, making a lot of noise. One person notes, "hearing, hearing" and goes back to their meditation, no problem, no hindrance. The other person hears the noise of the truck and starts thinking, "Ah, they're making too much noise here. Why do they not shut up, why do they let the truck come up?" and aversion comes. Aversion came because they were not mindful just to note, "hearing, hearing". Very simple. So that might be all the investigation we need, to encourage us that every time in the future when we're hearing the noise, we have to note, "hearing, hearing" and go back to our subject.