Digital SAT Writing: Logical Comparison and Parallel Elements

On the Digital SAT Writing and Language section, your ability to spot and fix subtle grammatical errors directly impacts your score. Among the most frequently tested error categories are logical comparisons and parallel elements. These concepts test whether you can ensure sentences compare like with like and that linked ideas are expressed in matching grammatical form. Mastering them is non-negotiable for a high score, as they appear in multiple questions per test and trap unprepared test-takers with seemingly correct but structurally flawed sentences.

What is a Logical Comparison?

A logical comparison occurs when two or more similar, comparable things are contrasted or equated. An illogical comparison happens when the sentence mistakenly compares unlike or incommensurate items, creating confusion or absurdity. The core rule is simple: you can only compare things that belong to the same category.

The most common error involves using a possessive noun or pronoun incorrectly. Consider this faulty sentence: "The novel's plot is more engaging than the movie." This compares a plot (a thing) to a movie (an entire work). The comparison is illogical. The correction makes the items parallel: "The novel's plot is more engaging than the movie's plot" or, more concisely, "the movie's."

Your correction strategy is a two-step process:

1. Identify the two items being compared. Look for comparison words like than, as, similar to, different from, like, and unlike.
2. Ask: "Are these items the same kind of thing?" If not, you must rewrite one side of the comparison to match the other.

Faulty: Her dedication to running is greater than her sister. Analysis: This compares dedication to a person. Correct: Her dedication to running is greater than her sister's [dedication].

Faulty: The rules of chess are more complex than checkers. Analysis: This compares rules to a game. Correct: The rules of chess are more complex than those of checkers.

Mastering Parallelism in Lists and Series

Parallelism is the grammatical principle that elements sharing the same functional role in a sentence must share the same grammatical form. In a list or series, every item must be a noun, a verb phrase, a prepositional phrase, an infinitive, or a gerund—but you cannot mix and match.

The SAT will present you with sentences where the items in a series are grammatically mismatched. Your job is to recognize the pattern established by the first item and enforce it on the others.

Faulty: For a healthy lifestyle, the doctor recommended a balanced diet, exercising regularly, and to sleep eight hours. Analysis: The series mixes a noun phrase ("a balanced diet") with a gerund phrase ("exercising regularly") and an infinitive phrase ("to sleep eight hours"). Correct: For a healthy lifestyle, the doctor recommended a balanced diet, regular exercise, and eight hours of sleep. (All noun phrases) Also Correct: For a healthy lifestyle, the doctor recommended eating a balanced diet, exercising regularly, and sleeping eight hours. (All gerund phrases)

When a series follows a preposition or verb, the parallel structure must continue. For example, if a sentence begins "She is skilled at...," everything that follows "at" must be in the same form.

Navigating Correlative Conjunctions

Correlative conjunctions are paired words that link two balanced elements. The most common pairs tested are both/and, either/or, neither/nor, not only/but also, and whether/or. The rule is strict: the grammatical structure immediately following the first part of the pair must be identical to the structure immediately following the second part.

The SAT often separates these conjunctions with many words, making the error harder to spot. Use a mental "bookmark" technique: when you see both, immediately look for and and check the words that come right after each.

Faulty: The strategy was designed both to reduce costs and for improving efficiency. Analysis: After both we have an infinitive ("to reduce"). After and we have a prepositional phrase ("for improving"). They are not parallel. Correct: The strategy was designed both to reduce costs and to improve efficiency. (Infinitives) Also Correct: The strategy was designed both for reducing costs and for improving efficiency. (Prepositional phrases with gerunds)

Faulty: The new manager not only reorganizes the department but also staff morale is boosted. Analysis: After not only we have a verb ("reorganizes"). After but also we have a new subject and verb ("morale is boosted"). The clauses are not parallel. Correct: The new manager not only reorganizes the department but also boosts staff morale. (Both verbs: reorganizes, boosts)

Common Pitfalls

1. The Missing Possessive: Forgetting to add 's to the second item in a comparison is the most frequent logical comparison error.

• Pitfall: "My car's mileage is better than David." (Illogically compares mileage to a person).
• Correction: "My car's mileage is better than David's."

1. The Mismatched Series Starter: Beginning a series with one grammatical form and unconsciously switching mid-stream.

• Pitfall: "Her responsibilities include training new employees, to update the website, and customer service." (Gerund, infinitive, noun).
• Correction: "Her responsibilities include training new employees, updating the website, and providing customer service." (All gerunds).

1. The Distracting Correlative: Letting words between the correlative conjunctions obscure the structural mismatch.

• Pitfall: "We will either go to the library or studying at home." ("Go" is a verb, "studying" is a gerund).
• Correction: "We will either go to the library or study at home." (Both verbs).

1. The Implied but Missing Word: Assuming the reader will mentally fill in a word that isn't actually present, creating an illogical comparison.

• Pitfall: "The climate here is drier than the coast." (Illogically compares climate to coast).
• Correction: "The climate here is drier than that of the coast."

Summary

• Logical comparisons require comparing similar things. Always check that the nouns or noun phrases on each side of than, as, or like belong to the same category, often requiring a possessive ('s) to make the items parallel.
• Parallel elements in a list or series must share an identical grammatical form (all nouns, all verbs ending in -ing, all infinitives, etc.). The first item in the series sets the pattern for all that follow.
• Correlative conjunctions (both/and, either/or, not only/but also) demand strict grammatical symmetry. The words or phrases that come immediately after each half of the pair must match in structure.
• Your most powerful tool is isolation. When checking for errors, mentally block out the extra words between the key elements to see if the core structures align logically and grammatically.