Dickinson is a poet who is renowned for her use of the dash in her poetry, which serves generally to break up her short verses and also, in the case of poems that end with a dash, create a sense of unfinished thoughts or images that can actually be quite disturbing. Consider the example from this brilliant poem where Dickinson turns her attention to "madness" and deliberately uses a number of terms that are highly ambiguous in society:
In this, as all, prevail--
Assent--and you are sane--
Demur--you’re straightway dangerous--
And handled with a Chain--
The dashes create a syncopated style that serve to highlight key words, such as "Assent" and "Demur," which, in Dickinson's view, are the two options that humans have in the face of the views of "the majority." In addition, however, note the way that the poem ends with a dash, which does not allow a sense of closure in any way. By ending the poem with a dash, Dickinson denies her audience a neat ending that wraps up her poem, and the reader is left with the image of somebody who is actually sane who is nonetheless treated as if they were insane, and treated very brutally, as is suggested by "handled with a Chain."