When we speak, there are often small pauses between syntactic units such as sentences. In writing, these pauses are signified by punctuation:
I can come if you want. (without pause)
I can come, if you want. (with brief pause)
I can come. If you want. (with longer pause)
But sometimes we briefly hesitate in the middle of syntactic units, for example, when we hesitate to utter a word that the listener might find objectionable:
This man, this (pause) monster, has done something despicable.
We can italicize such a word, as I have done, to show an emphasis. But that emphasis does not necessarily imply a pause:
This man, this monster, has done something despicable. (emphasis, but no pause)
This man, this...monster...has done something despicable. (pause, but no emphasis)
But the last example shows why using an ellipsis to signify a pause may be confusing. A reader, who does not know what I want to say, may wonder whether I have left out words before and after "monster", or if I mean that the speaker is trailing off twice, creating two longish pauses. The last example may look to a reader more like two broken off sentences instead of one sentence with two pauses:
This man, this... What a monster... He has done something despicable.
A full stop has been better used to create unmistakeable pauses in unconventional places:
I am going to tell you one last time: Go. Home. Now.
But a full stop is too strong a disruption in some cases. Usually, because we lack a specific symbol for a brief hesitation, we describe it:
This man, this -- I briefly hesitate -- this monster, has done something despicable.
But again, this inserted description is not exactly the same as a brief hesitation.
So how can I show a brief hesitation, for example surrounding the word "boy" in the following example?
I was expecting the president to be a middle aged man and then this (hesitation) boy (hesitation) comes in.
I have thought about this problem in my answer to a related question, but that question itself is broader than my current problem and can be easily solved through description.