Logical reasoning PrepTest 136 · Section 2 · Question 23

Incorrect. This still wouldn't explain why they're grooming themselves instead of each other considering the similarities to primates and the need to maintain social cohesion. Sure, they may be clean because they clean themselves, but the stimulus specifically notes that the purpose of grooming is maintaining social cohesion, not cleanliness.

Correct. Argument or Facts:
Facts

Question Type:
Paradox

Stimulus Summary:
Primates - Social group size is positively correlated with neocortex size and time spent grooming each other.
Humans - Large neocortexes, large social group, no time grooming each other.

Answer Anticipation:
This stimulus presents information about two groups—primates and early humans—in a way that allows for a comparison.

There are similarities—they have social groups that are a certain size, and that size is correlated with neocortex size. In primates, these two things are also correlated with a lot of time spent grooming each other.

However, unexpectedly, early humans spent almost no time grooming each other! That's the discrepancy we're meant to resolve—if primates and humans both have social groups and neocortexes that seems to be related to each other, why don't they share this grooming habit that is related to the other two in primates?

While that framing of the paradox would be enough to head to the answer choices, we can go a step further because of an additional piece of information presented in the stimulus—that the main purpose of this grooming was the maintenance of social cohesion. Since the discrepancy we need to explain is early humans not grooming each other, it's likely that the correct answer will highlight another mechanism used by them to maintain social cohesion. And it's likely something that the primates can't do.

Answer Explanation:
This answer establishes that early humans achieved the purpose of social grooming without the grooming. And they did so through something that primates don't have—language. This answer explains the discrepancy by highlighting a relevant difference.

Key Takeaway:
Paradox questions frequently deal in comparisons, highlighting a pair of things that are similar in many ways with an unexpected difference, or different in many ways with an unexpected similarity. Unexpected similarities are usually explained with other similarities, and unexpected differences with other differences.

Incorrect. While they may have had less of a need for social grooming to maintain cleanliness, it doesn't explain why they didn't do it anyway to maintain social cohesion. The relationship between group size, neocortex size, and social grooming is the baseline for the comparison, and cleanliness doesn't factor into that.

Incorrect. Just because they hunted in small groups doesn't undermine their need to maintain social cohesion in the larger groups they lived in.

Incorrect. This makes the discrepancy worse by highlighting the variety of primates that have large neocortexes and engage in social grooming. Why are humans so unique in not engaging in the practice?