Writing Tip

Faulty Punctuation Sends Reader up the Garden Path

Difficulty Level: Advanced

Recommendation: Use Commas to Prevent Misreading and “Garden-Path” Sentences

Part 1: Joining Independent Clauses

Sometimes, when you omit a comma, you can mislead the reader. When you want to join two independent clauses with a coordinating conjunction (and, or, yet, and so on), you must use a comma as well. Not doing so can create what is called a garden-path sentence, because the author has led the reader up the garden path and abandoned her among words that seem irrelevant to the context.

The following sentence illustrates how faulty punctuation can lead to a garden-path sentence:

Here, two independent clauses are separated by and. But separation requires more than just and. A comma is also required to prevent misreading and facilitate fluid reading. Without the comma, the material in the first clause sprawls into the next. The term “estimation errors” is likely to be wrongly predicted as an object of the verb to perform. That is, “these values are used to perform” two things: fault location and estimation errors. (Click to See/Hide Diagram)

Part 2: Joining Dependent Clauses and Phrases

Omitting a comma when adding nonessential material to a sentence can cause a garden-path sentence. How do you know whether material is nonessential? If the main clause does not require the additional material to complete its meaning, then the additional material is nonessential. Nonessential material should be set off with a comma. Consider:

This sentence includes a nonessential phrase at the end: “leading to improvement in accuracy.” It is not required to complete the meaning of the main clause. Can you delete the phrase without altering the meaning of the main clause? Yes. You can delete it without consequence. And, if this nonessential phrase is not joined to the main clause with a comma, the sentence can be misread. Specifically, the reader may assume that the phrase modifies locations, which it does not. With a comma after locations, the reader understands that the phrase modifies the entire main clause. (Click to See/Hide Diagram)

Read the Full Commentary