The Langston Hughes poem “Harlem,” also sometimes referred to as “A Dream Deferred,” is about the potentially devastating effects of oppression.
There are a number of possible critical approaches you could take to examine this poem: formal, historical, psychological, sociological, or reader-response are some that seem to lend themselves readily. If I were to pick two from that list, I would choose formal and psychological.
Formal analysis: This kind of analysis looks at how the poem is structured. “Harlem” is particularly interesting in this regard because of the way Hughes put it together. It starts with a provocative but seemingly innocuous (harmless) question: “What happens to a dream deferred?”
Then it follows with four more questions in rapid fire. These questions are similes, comparing a deferred dream to something that could “dry up,” or “fester,” or “stink,” or “crust.”
Notice that after the fourth simile, Hughes uses the manipulation of physical space to help make his point—he skips an extra line for emphasis. Then he presents another simile, but the pacing changes because this one is not phrased as a question—it is more like conjecture, as if he is finally coming to his ultimate point. Then he skips another line, switches to italics, and presents another question. But the tone of this question is different: “Or does it explode?”
After the series of similes, Hughes has changed up and used a metaphor, and not just any old metaphor. This is an implied metaphor, because it hints at its meaning without revealing it entirely. Using the word “explode” implies that a dream deferred could be a bomb just waiting to go off, as if violence could be the ultimate result, the answer to all of the questions we just read.
Also notice that after the first simile the entire poem is indented. This gives primacy to the first line, while everything else addresses the idea of the dream deferred. Hughes wants to keep you focused on that question.
Psychological analysis: To analyze a work in terms of psychology you have to look at how the poem addresses the inner life (mentally or emotionally) of the subject or speaker. For such a short little poem, Hughes certainly says a lot about what goes on inside the head of “Harlem's” speaker. The introductory question, as noted above, seems simple enough. But to show how a dream deferred can eat away at someone, causing frustration and resentment, Hughes hits the reader with the five subsequent similes, which are generally building toward the potentially violent ending. These similes get us into the mind of the speaker—how he thinks and feels about what is happening to him.
If we were to restructure this poem in terms of its psychological message and present it as a basic prose statement, it would say something like this: What happens to the dream of someone who is denied the hope of achieving the dream? Does the dream wither away, or just weigh on the person, or does it create a building anger and frustration that may someday result in violence?
Hughes is asking us to consider how the mind is affected by a life of hopelessness and what the result of that effect might be.
When I teach this poem, I use both critical approaches. But, for the sake of teaching students about how literary devices work, I focus a bit more on the formalist analysis. I like for students to see how the use of figurative devices like similes and metaphors, as well as the physical manipulation of space and the late switch to italics, can affect a reader's perception of the poem.