You’re great at grammar, right? You know your idioms, correlative conjunctions, and indirect objects by heart. You could probably teach about past present and future perfect tense to a room full of eighth graders.
But, when faced with the Sentence Correction section, you’re still getting 65% or 70% of questions right. If you’re fantastic at grammar, what gives?
Most test takers fail to recognize that, frankly, the GMAT is not assessing your ability to effectively mark up paper with a red pen. Even English teachers and copywriters find themselves in a pickle when it comes to the sentence corrections because, just like the problem solving and data sufficiency questions, the GMAT is assessing  something on a deeper level – the ability to communicate and articulate in a logical fashion… which, more often than not, falls into the category of sentence construction.
Let’s dive into a couple of examples to showcase what we mean:

Neuroscientists distinguish organic amnesia, which has some physical cause such as an occurrence of blunt force trauma to the head, from psychogenic amnesia, which is purely psychological in origin.

(A) organic amnesia, which has some physical cause such as an occurrence of blunt force trauma to the head, from psychogenic amnesia, which is purely psychological in origin
(B) organic amnesia from psychogenic amnesia, the first of which has some physical cause such as an occurrence of blunt force trauma to the head, and the second of which is purely psychological in origin
(C) between organic amnesia, in which they have experienced some physical cause such as an occurrence of blunt force trauma to the head, and psychogenic amnesia, which is purely psychological in origin
(D) between organic amnesia, which has some physical cause such as an occurrence of blunt force trauma to the head, and psychogenic amnesia, which is purely psychological in origin
(E) between organic amnesia, in which some physical cause exists such as an occurrence of blunt force trauma to the head, and psychogenic amnesia, which is purely psychological in origin

Many students will be completely fine with the way this sentence is constructed. Why, of course scientists distinguish organic amnesia from psychogenic amnesia! They are different, don’t you see!

But the beginning part of the sentence is not adequately structured and if we believe (A) is the right answer, then we are failing to think deeply about the meaning of words and how they correspond with other words in a sentence.

Let’s focus on the word “distinguish” and the fact that we are addressing a relationship between two items. A simple sentence that uses distinguish might be –

“He could barely distinguish a faint light beyond the forest.”

Distinguish is used to mean identify. This sentence has a similar usage of the word distinguish, but we are not assessing just one item, but two. We need that comparison word – between.

“He could barely distinguish between the light coming from the farmhouse and the light coming from the bonfire.”

Making a comparison with no comparison word? Poor sentence construction. From there, we should recognize that possible answers are (C) (D) and (E).  And then, in assessing (C) and (E) both answer choices utilize “in which.” In which, what does organic amnesia have something?

These are not right answers because organic amnesia cannot be “in” something and it wouldn’t be parallel in relationship to the rest of the sentence. Our correct answer is (D).

Sentence corrections really are about whether every single part of the sentence makes sense, beyond just being grammatically correct. Make sure to dissect and taking apart sentences, particularly hard ones, and decide whether each word relates to the next appropriately…particularly before selecting (A) and making no change.