Logical reasoning PrepTest 145 · Section 2 · Question 2

Incorrect. The conclusion explains the development of the calorie-hungry brain with cooking. If cooked food has an equivalent amount of calories to raw food, then that weakens an argument that it allowed the brain to develop since there would be no extra calories available (fewer, even, since it necessary takes energy to take raw food and cook it).

Incorrect. Since the argument explains the development of the brain through cooking, raw foods don't strengthen it.

Incorrect. Similar to (A), this answer creates an equivalency between raw foods and cooked foods, whereas the conclusion uses the development of cooking to explain how more calories were available to allow the brain to develop. If humans get only the same amount of calories from cooked foods as raw, then it's unclear how developing the ability to cook raw foods would help humans have more calories available.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Our big brains require a lot of calories. They developed around the same time as we started using fire. Those on a raw food diet have trouble eating enough. Therefore, cooking probably led to the big brains.

Answer Anticipation:
There are a lot of premises to this argument, but the conclusion is a causal explanation for an observed phenomenon.

That phenomenon? Humans have big brains and a relatively small gut, which creates some issues with getting enough calories from our food. The explanation? Cooking—we started using fire around the same time as our brains developed, and those who are on a raw food diet have a hard time eating enough.

Since this causal explanation is based on a correlation ("around the time"), we can look for our normal strengtheners with a correlation/causation jump:

(1) Eliminate an alternative cause/explanation
(2) More examples of cause and effect going together (though this seems unlikely given that other animals don't really cook)
(3) A control group Ð if a group of our ancestors branched out and didn't develop a big brain while not harnessing fire
(4) Explaining the causality Ð how does cooking lead to a big brain?

In this instance, the last answer actually seems likely (even though it's generally rare). The stimulus mentions that the brain requires a lot of calories, but the stimulus doesn't note why cooking should influence that. If we can find an answer that explains how cooking helps to get more calories with less food, it would help to justify the logic here.

Answer Explanation:
This answer states that cooking food allows more calories to be available for the brain because fewer are used to digest food. It provides an explanation for how cooking could lead to the development of the calorie-hungry brain, thus strengthening the argument.

Key Takeaway:
While rare, one way to strengthen an argument with a correlation/causation flaw is by explaining how the causality would work. It doesn't show up often, but it does often enough that you should be aware of it.

Incorrect. If anything, this answer suggests an alternative explanation for the development of the brain—humans domesticating animals, not humans developing cooking.