The Importance of Word Selection
In a well-known psychological experiment by Brewer and Treyens,  subjects were asked to temporarily wait in a professor’s office while he went to see if the previous subject had finished. The professor returned in less than a minute, took the subjects to another room, and then asked them to describe in writing what they had just seen in the professor’s office. The goal of the experiment was to test a concept known as a "schema" which is a short-hand, mental template used by people to make sense of things—in this instance, to make sense of the professor’s office. In this study, people responded with items that you would expect to see in a professor’s office: a desk, chair, bookshelves, etc. A select few noted a skull that was present; and only one person out of the thirty noted a picnic basket. A third of the participants, however, listed books, despite the fact that there were none.
What this experiment showed was the strength of the "Professor’s Office Schema" and how it can override reality—as in the case of the non-existent books. As mentioned, a schema is a template that people use to short-hand their surroundings. Rather than take note of every detail of an object, for example the chair or couch you are sitting on at present, people make assumptions based upon past experience. When you think of the enormous number of objects encountered daily, this is an effective way to organize the huge amounts of data into manageable pieces.
This has applications beyond psychology. It has relevance whenever we use one thing to stand in for another, such as in the case of language. As poets of a short form, a critical choice we make in each poem is the selection of words. However, words have different experiential meanings to different people, so the use of "tree" in a poem might conjure a pine, oak, or any other species depending upon who is reading the poem. Further, in the case of haiku, our need for clarity has to be balanced by economy. Consider a poem such as John Wills’ 
leans upon the snag
Words such as "river" and "snag" and even "moment" are all vague approximations. Someone with little experience (no schemas) of rivers could easily ask: what kind of river? Wide like the Mississippi or narrow like the Merced where it passes through Yosemite Valley? The poem wouldn’t be nearly as effective if Wills had padded it with modifiers. We take a certain amount of pride in saying that haiku are poems of inference, and that as poets we use the slightest brush to paint a detailed mural. In that we need to be conscious of our word choices.
1. Brewer, W. F., & Treyens, J. C. (1981). Role of schemata in memory for places. Cognitive Psychology, 13, 207-230
2. Wills, J. Reed Shadows. Windsor, ON: Black Moss/Sherbrooke, QC.: Burnt Lake Press, 1987.