How we change what others think, feel, believe and do
Use the intensifier to subtly suggest to the other person what emotions they should feel.
In the same way, you can also use adverbs to attenuate and reduce the natural emotional content of a verb.
That is very interesting. (basic intensifier)
The basic intensifier is 'very' and can be used with many verbs. Other intensifiers often have the same meaning as 'very' but use different forms Intensifiers include: very, really, extremely, remarkably, fantastically, etc.
Suggesting what to feel
Intensifiers often subtly suggest to the other person what to feel. By naming emotions within the adverb, the other person has to consider this emotion and hence begins to feel it.
As the adverb is not the subject, object or verb, it is not as noticed and hence such suggestions may slip past conscious (or even subconscious) filters.
Just as intensifiers increase emotion, the same effect can be done in reverse, where the natural level of emotion implied by a verb may be reduced. This can be done deliberately to cool down a situation. It also can appear in floppy language, where you are seeking to avoid saying anything that upsets the other person and hence end up making very weak statements that have a very low chance of changing anybody's mind.
Borrowing from the negative
There is a curious pattern of intensification that uses negative words to intensify positive verbs. These words include: Awfully, dreadfully, fearfully, terribly, ridiculously, insanely, disgustingly, hideously, etc.
Thus, for example:
She is dreadfully beautiful.
What in effect is happening here is that many strong emotions are negative, so using them in a positive context borrows that intensity of emotion whilst the contextual cues show that the real meaning is positive. An additional effect is that combining negative and positive words in the same sentence creates confusion, which itself is also adds to the emotion.
A curious fact about this usage is that it is particularly popular with upper-class British people. What a ridiculously interesting thing!
De-intensification by intensification
Sometimes intensification is done deliberately but with the opposite intent. This use of sarcasm may be done against another person or used in a more ironic sense about the situation.
Oh, very clever! (actually meaning rather stupid)