Watch What You Infer

GMAT.London blog
October 13, 2015

Watch What You Infer


Watch What You Infer

You are in-fer a treat with this post. Well, things can only get better after that pun. Let’s get started…

The primary and secondary definitions of infer are ‘to derive from reason’ and ‘lead to’, respectively. The next two definitions, in contrast, that the dictionary gives are ‘to guess’ and ‘to suggest’.

Many GMAT students believe that, when they see the word ‘infer’ in a GMAT reading comprehension or critical reasoning question, they should answer based on those last two definitions.

Students might pick an answer because they personally believe the statement to be accurate or because it vaguely seems right. You should be much more confident about your answer than that. You should have clear evidence supporting it.

For the GMAT, ‘infer’ emphatically does not mean ‘suggest’, it means ‘directly leads to, based on reasoning and logic.’

Prick up your ears when you hear any facts, factual statements or numbers.

Let’s given you a condensed, Official-GMAT-type reading comprehension question and show you the typical answer choices:

A dog’s nose can, on average, smell better than a human nose by a factor of ten thousand; dogs’ olfactory powers have even been used to detect cancer cells. Glands inside the nose ensure that the nose is kept wet and this moisture means that scents are better captured and registered. Another difference between a human nose and a dog’s nose is in the fact that dogs do not exhale through their nostrils and instead exhale through slits in the side of their nose.

It can be inferred from the passage that which of the following is true:

  1. A human would not be able to detect cancer cells using their nose alone.
  2. Hospitals should use more sniffer dogs than they do.
  3. Humans do not directly exhale through their nostrils.
  4. A dog could detect a single milligram of sugar in a coffee cup, even if a human couldn’t smell ten grams.
  5. A scent is more likely to be smelt, in general, by a wet nose than a dry nose.

Here we have the typical Inference answer set. I call them…

The Plausible: A) It contains a fact we all know to be very likely true. It might also be suggested from the statement that ‘A dog’s nose can typically smell better than a human nose by a factor of ten thousand’ and that their powers of smell ‘have been used to detect cancer’. But did the passage give us direct evidence that humans could not smell cancer cells? No. Therefore this answer choice is plausible and yet wrong.

The Unrelated Subject: B) This choice is about hospitals. That’s an unrelated subject (not a dog or human) and therefore wrong. You should be able to quickly eliminate this option.

The Opposite: C) The passage said that a difference between dogs and humans was that dogs do not exhale through their nostrils. Therefore this choice is the opposite of what can be inferred.


The Unrelated Object: D) The choice involves dogs (right subject) but it tries to bring in a feat that we have no direct evidence to reason that a dog can accomplish.

The Correct Answer: E) ‘Glands … ensure that the nose is kept wet and this moisture means that scents are better captured and registered.’ Here is our direct evidence.

Now, things won’t always be in this order, and the GMAT powers above might throw in a couple of opposites or three plausible suggestions. But now you know what the red herrings look like.

What we’ve learnt:

  • Now we know exactly what the wrong answers look like. This will help spotting the correct one.
  • Inference demands evidence. Direct evidence.

Now, go find some inference questions and destroy them!

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