Researcher: During the rainy season, bonobos (an ape species closely related to chimpanzees) frequently swallow whole the rough-surfaced leaves of the shrub Manniophyton fulvum. These leaves are likely ingested because of their medicinal properties, since ingestion of these leaves facilitates the elimination of gastrointestinal worms.
Summarize Argument: Phenomenon-Hypothesis
The researcher hypothesizes that bonobos eat Manniophyton fulvum leaves during the rainy season because they have medicinal properties. For evidence, he points to one such property: the leaves help eliminate gastrointestinal worms.
Notable Assumptions
The researcher assumes bonobos eat Manniophyton fulvum leaves because of their medicinal properties, and not for some other reason. This means assuming bonobos benefit from having fewer gastrointestinal worms and that the leaves are not worth eating just for their nutritional value.
A
Bonobos rarely swallow whole leaves of any plants other than M. fulvum.
This suggests there’s something unique about M. fulvum leaves—but not necessarily their medicinal value. It makes bonobos’ ingestion of these leaves more anomalous, but throws no weight behind the researcher’s particular hypothesis.
B
Chimpanzees have also been observed to swallow rough-surfaced leaves whole during the rainy season.
This is irrelevant. It doesn’t say chimpanzees eat M. fulvum leaves in particular, nor does it imply chimpanzees eat those leaves for their medicinal properties.
C
Of the rough-leaved plants available to bonobos, M. fulvum shrubs are the most common.
This doesn’t suggest bonobos eat them for their medicinal value. It’s equally compatible with the leading alternative hypotheses—for example, that bonobos eat the leaves for their nutritional value.
D
The leaves of M. fulvum are easier to swallow whole when they are wet.
This implies bonobos would prefer to eat M. fulvum leaves during the rainy season, rather than the dry season—but not why they choose to eat them in the first place. It doesn’t say the leaves have greater medicinal value when wet.
E
The rainy season is the time when bonobos are most likely to be infected with gastrointestinal worms.
This suggests M. fulvum leaves have more medicinal value to bonobos during the rainy season, since those leaves are more likely to rid them of worms. It makes it more likely the bonobos eat the leaves for their medicinal properties, as opposed to nutritional or other reasons.
Summarize Argument
The author concludes that Justine has syndrome Q. He supports this by saying that if someone has syndrome Q, they test positive, and Justine tested positive.
Identify and Describe Flaw
This is the cookie-cutter flaw of confusing necessary and sufficient conditions. The author treats “positive” as sufficient for “syndrome Q,” but according to his premises, “positive” is necessary.
In other words, just because Justine tested positive doesn’t necessarily mean that she has syndrome Q. She might just have had a false positive test.
In other words, just because Justine tested positive doesn’t necessarily mean that she has syndrome Q. She might just have had a false positive test.
A
It confuses the claim that a subject will test positive when the syndrome is present with the claim that any subject who tests positive has the syndrome.
The author treats testing positive as sufficient for having syndrome Q. But his premises say that it’s necessary: if someone does have syndrome Q, then they will test positive, not the other way around. So Justine might not have syndrome Q, even though she tested positive.
B
It makes a general claim regarding the accuracy of the test for syndrome Q without providing adequate scientific justification for that claim.
The author claims that the test is accurate and positive when someone does have syndrome Q. He doesn’t necessarily need to provide scientific justification for this, but he does say that research has proven it to be true.
C
It fails to adequately distinguish between a person’s not having syndrome Q and that person’s not testing positive for syndrome Q.
Instead, the author fails to distinguish between a person testing positive for syndrome Q and that person having syndrome Q. He doesn’t mistake a person not having syndrome Q with that person not testing positive for it.
D
It confuses a claim about the accuracy of a test for syndrome Q in an arbitrary group of individuals with a similar claim about the accuracy of the test for a single individual.
The author never confuses his claim about the test’s overall accuracy with his claim about Justine’s test. Also, we have no reason to believe that the research used an “arbitrary group” when measuring the test’s accuracy.
E
It confuses the test’s having no reliable results for the presence of syndrome Q with its having no reliable results for the absence of syndrome Q.
If someone does have syndrome Q, then they test positive. So the test does have reliable results for the presence of syndrome Q. We don’t know whether it has reliable results for the absence of syndrome Q, but regardless, the author never confuses the ideas presented in (E).
Summarize Argument: Phenomenon-Hypothesis
The author concludes that eating lots of fat, processed sugar, or alcohol, can contribute to heart disease. This is based on the fact that these things increase blood triglyceride levels, and the hypothesis that higher blood triglyceride increases the risk of heart disease. This hypothesis is based on research that shows a correlation between blood triglyceride levels above 1 milligram per millileter and higher likelihood of heart attacks.
Notable Assumptions
The author assumes that there’s no other explanation for the correlation observed betwen blood triglyceride levels and heart attacks. The author also assumes that there aren’t other things in fat, processed sugar, and alcohol that tend to decrease the risk of heart attacks.
A
People with a high-fat diet who engage in regular, vigorous physical activity are much less likely to develop heart disease than are sedentary people with a low-fat diet.
This suggests physical activity is also a causal factor in heart disease. But this doesn’t suggest high fat consumption isn’t also a causal factor. (A) could have been correct if we knew that people with high blood triglyceride on average exercise a less than others.
B
Triglyceride levels above 2 milligrams per milliliter increase the risk of some serious illnesses not related to heart disease.
Other diseases aren’t relevant to whether triglyceride levels are a causal factor in heart disease.
C
Shortly after a person ceases to regularly consume alcohol and processed sugar, that person’s triglyceride levels drop dramatically.
This strengthens the connection between consumption of alcohol/sugar and triglyceride. This is consistent with the author’s reasoning.
D
Heart disease interferes with the body’s ability to metabolize triglycerides.
This suggests an alternate explanation for the correlation between higher blood triglyceride levels and heart attacks. If heart disease interferes with triglyceride metabolization, it would lead to higher blood triglyceride. This suggests the cause and effect could be reversed.
E
People who maintain strict regimens for their health tend to adopt low-fat diets and to avoid alcohol and processed sugar.
This has no impact, because we don’t know whether the people on these low-fat and low-sugar diets are more or less likely than others to have heart attacks.
Summarize Argument: Counter-Position
Some historians conclude that recipes compiled by Apicius are a reliable indicator of how wealthy Romans made their food. The author’s conclusion is that the historian’s conclusion isn’t necessarily true. This is because only a few other recipes from Apicius’s time have survived, and Apicius’s recipes may be unrepresentative of ancient Roman food. The author also relies on an analogy to many modern chefs; just as their recipes are unusual, so too might be Apicius’s.
Describe Method of Reasoning
The author criticizes the historian’s conclusion by pointing out that it might be based on an unrepresentative sample of recipes. The author also relies on an analogy to support the possibility that the sample is unrepresentative.
A
It rejects a view held by some food historians solely on the grounds that there is insufficient evidence to support it.
Calling a conclusion “too hasty” is not the same as rejecting it. The author doesn’t necessarily believe the historians are wrong; he’s simply pointing out they might be wrong. Also, the author relies on an analogy; not “solely” on the claim that there’s insufficient evidence.
B
It offers support for a view held by some food historians by providing a modern analogue to that view.
The author does not support the historians’ view. He points out that there are reasons to think it might not be true.
C
It takes issue with the view of some food historians by providing a modern analogue that purportedly undercuts their view.
The author takes issue with the view of the historians (”the conclusion is too hasty”) by providing a modern analogue (”many notable modern chefs”) that purportedly undercuts the historians’ view (suggesting that Apicius’s recipes might be unrepresentative).
D
It uses a conclusion drawn by some food historians as the basis for a conclusion about a modern analogue.
The author’s conclusion is not about the modern chefs. The modern chefs are used as support for the conclusion that the historian’s conclusion is too hasty.
E
It tries to bolster a conclusion about the similarity of historical times to modern times by comparing a conclusion drawn by some food historians to a modern analogue.
The conclusion is not about the “similarity of historical times to modern times.” The author uses an analogy to modern chefs to conclude that we do not necessarily know that Apicius’s recipes are representative of the food of wealthy ancient Romans.