"Surprising" Phenomenon
Why have farmers in many parts of the world who transitioned from traditional nonhybrid crops to hybrid crops not seen an increase in crop yields after transitioning?
Objective
The correct answer must identify why transitioning to hybrid crop strains has not increased crop yields for farmers in many areas of the world when hybrid crops produced significantly higher crop yields than traditional nonhybrid crops planted alongside them in test plantings.
A
Most farmers who plant the hybrid strains of their crops have larger farms than do farmers who continue to plant traditional nonhybrid strains of the same crops.
The size of the farms that hybrid strains are planted on relative to the size of the farms their nonhybrid alternatives are planted on tells us nothing about why transitioning to hybrid strains has not increased crop yields for farmers in many parts of the world.
B
Hybrid strains of crops produced higher yields in some areas than did nonhybrid strains in those areas.
Knowing that hybrid strains have produced higher yields than nonhybrid strains in some areas doesn’t help explain why the farmers discussed in the stimulus have seen no increase in their crop yields.
C
The hybrid strains were tested under significantly better farming conditions than are found in most areas where farmers grow those strains.
If this is true, the production levels of hybrid crops during the test plantings could’ve been unrepresentative of how much hybrid crops typically produce in the areas where farmers grow those hybrid crops.
D
Many traditional nonhybrid strains of plants produce crops that taste better and thus sell better than the hybrid strains of those crops.
The taste and salability of nonhybrid strains of plants tell us nothing about the size of yields produced by those plants or hybrid strains of those plants.
E
Many governments subsidize farmers who plant only hybrid strains of staple crops.
Government subsidies given to farmers of hybrid crops have nothing to do with the yield size of those crops.
Summarize Argument: Phenomenon-Hypothesis
The researchers hypothesize that folate and B6 hinders the development of heart disease in women. This is based on a phenomenon shown in a recent study of female physicians: the more folate and B6 they had in their diet, the less likely they were to develop heart disease (and vice versa).
Notable Assumptions
The researchers assume that it is the folate and B6 in the female physicians’ diets that are preventing them from developing heart disease, as opposed to some other factor(s) in their diets or lifestyles.
A
The foods that contain significant amounts of the vitamins folate and B6 also contain significant amounts of nonvitamin nutrients that inhibit heart disease.
This weakens the researchers’ conclusion. It attacks their assumption that the B6 and folate are the critical factors that inhibit heart disease in the female physicians, as opposed to some other factor—in this case, significant amounts of nonvitamin nutrients.
B
It is very unlikely that a chemical compound would inhibit coronary disease in women but not in men.
This does not affect the argument. It may be that the researchers’ hypothesis is very unlikely, but that alone doesn’t make it any less convincing.
C
Physicians are more likely than nonphysicians to know a great deal about the link between diet and health.
This does not affect the argument. While physicians’ knowledge about how diet impacts health may influence their dietary choices, it should not affect how the vitamins in their diet influence their health, which is what the study is about.
D
The physicians in the study had not been screened in advance to ensure that none had preexisting heart conditions.
This does not affect the argument. (D) does not offer reason to suspect that physicians with preexisting heart conditions confounded the study’s results—we would have to assume that they also didn’t eat a lot of B6 and folate for there to be any potential weakening effect.
E
The vitamins folate and B6 are present only in very small amounts in most foods.
This does not affect the argument. The amount of folate and B6 in most foods can be minimal without weakening the researcher’s hypothesis that they still have the effect of inhibiting the development of heart disease.
Summarize Argument: Phenomenon-Hypothesis
The psychiatrist concludes that traumatic events do not contribute at all to the development of phobias. His reasoning is that not all phobia suffers have trauma, and not all trauma victims have phobias.
Identify and Describe Flaw
The psychiatrist assumes that, for trauma to cause phobias, each trauma must be linked to a phobia, and vice versa. But a causal relationship doesn’t require an absolute connection to be valid (unlike a conditional one). For example, consider how smoking causally decreases life expectancy. That doesn’t mean that everyone who smokes dies young, or that everyone who will die young smokes.
A
treats the cause of the occurrence of a type of phenomenon as an effect of phenomena of that type
The psychiatrist is denying the very existence of a causal relationship, so confusing cause and effect can’t be the flaw.
B
presumes, without providing justification, that some psychological events have no causes that can be established by scientific investigation
The psychiatrist is denying one proposed explanation for a class of events; he isn’t saying that no causal explanation of them is possible.
C
builds the conclusion drawn into the support cited for that conclusion
This is the cookie-cutter flaw of circular reasoning; it isn’t applicable here, because the author’s conclusion and premises are distinct.
D
takes for granted that a type of phenomenon contributes to the occurrence of another type of phenomenon only if phenomena of these two types are invariably associated
The psychiatrist assumes that, for traumas to play any role in causing phobias, there must be an absolute link between the two. But the bar for causality isn’t that high. X can be a partial cause of Y even if X and Y don’t always appear together.
E
derives a causal connection from mere association when there is no independent evidence of causal connection
On the contrary, the psychiatrist is denying that a causal connection exists, so this can’t be the flaw.
Summarize Argument
The author argues that a decrease in an indicator species’ population should not always be attributed to pollution. While a decline in one of these species could be because of pollution, it could also result from the ecosystem naturally evolving, as change and evolution are constant, natural processes.
Identify Conclusion
The conclusion is that a decrease in the population of an indicator species should not always be credited to pollution: “environmentalists would be misguided if they attributed the loss of a population to pollution in all cases.”
A
Environmentalists sometimes overreact to the loss of a specific population.
The author does not claim that environmentalists overreact to the loss of a specific population.
B
The loss of a specific population should not always be interpreted as a sign of environmental degradation.
This rephrases our conclusion. It tells us that a decrease in a specific population should not be attributed to pollution in every case.
C
Environmentalists’ use of indicator species in tracking the effects of pollution is often problematic.
The author’s conclusion is not that the use of indicator species in tracking the effects of pollution is inherently problematic, but that environmentalists should not attribute population loss to pollution in every single case.
D
The loss of a specific population is often the result of natural changes in an ecosystem and in such cases should not be resisted.
The author does not make any claim about whether population loss should be resisted.
E
The loss of a specific population as a result of pollution is simply part of nature’s status quo.
The author makes a distinction between population loss due to environmental degradation and population loss due to natural evolution. (E) confuses these ideas and makes an incorrect claim.
Summarize Argument
The columnist concludes that some jurors must not have believed Tagowa’s testimony. His reasoning is that she stated after testifying that she believes Pemberton is guilty, while the jury found Pemberton not guilty.
Identify and Describe Flaw
We don’t know what Tagowa was called to testify about. Therefore, contrary to the columnist’s assumption, we don’t know if her testimony indicated that she thought Pemberton was guilty. It’s thus possible that the jurors both believed her testimony and found Pemberton not guilty.
A
It overlooks that a witness may think that a defendant is guilty even though that witness’s testimony in no way implicates the defendant.
Tagowa’s testimony could have been entirely unrelated to her reasons for believing that Pemberton is guilty. If so, the jurors could have believed Tagowa while still finding Pemberton not guilty.
B
It confuses facts about what certain people believe with facts about what ought to be the case.
This is the cookie-cutter flaw of confusing is with ought; it isn’t applicable here, because the author never makes a claim about what ought to be the case.
C
It presumes, without providing warrant, that juries find defendants guilty only if those defendants committed the crimes with which they are charged.
The columnist never opines on the actual guilt of Pemberton, so this can’t be the flaw.
D
It presumes, without providing warrant, that a jury’s finding a defendant not guilty is evidence of dishonesty on the part of someone who testified against the defendant.
The columnist concludes that the jury didn’t believe Tagowa, not that they thought she was dishonest. You can disbelieve a statement without questioning the speaker’s honesty.
E
It fails to consider that jury members sometimes disagree with each other about the significance of a particular person’s testimony.
The columnist does consider this: he concludes that not all jury members believed Tagowa’s testimony. This suggests that jurors disagreed about how much significance to attach to her testimony.
Summary
This new tax law intends to increase the amount of forested land in the region.
The law offers tax incentives for lumber companies for each unit of cleared land that they reforest.
A company purchased a large area of already cleared land and reforested it in order to receive the tax incentives.
The company paid for this purchase by clearing a larger tract of land in the region that it had originally planned to hold in long-term reserve.
Notable Valid Inferences
The tax law incentivized the lumber company to clear more land than it otherwise would have. In order to buy and reforest a large tract of cleared land, the company cleared an even larger tract of land that it had intended to hold in reserve. This is a net-loss in forested area.
A
It is a failure in encouraging the reforestation of cleared land in the region.
This could be false. This is too broad. The stimulus only discusses the actions of one company; we don’t know enough to say whether the new law was a failure overall. Further, in this case, the law actually did encourage the company to reforest a large tract of cleared land.
B
It will have no immediate effect on the amount of forested land in the region.
This could be false. Even in the example with the company, we can see that the law had an effect on the amount of forested land in the region (a net loss).
C
It will ultimately cause lumber companies to plant trees on approximately as much land as they harvest in the region.
This could be false. Since we only know about the actions of one company, we can’t make any definitive claims about what the ultimate result of the new law will be.
D
It can provide a motivation for companies to act in a manner contrary to the purpose of the law while taking advantage of the tax incentives.
This must be true. The law encouraged the company to act in a way that resulted in a net loss of forested area, even though the intent of the law was to increase the amount of forested land.
E
It will provide lumber companies with a tax incentive that will ultimately be responsible for a massive decrease in the number of mature forests in the region.
This could be false. Similar to (C), since we only have the description of the actions of one company, we can’t make any claims about what the overall results of the law will be.
A
confuses a necessary condition for the museum’s remaining open with a sufficient condition for the museum’s remaining open
The only conditional relationship in the trustee’s argument is between “low attendance” and “going bankrupt and closing permanently.” We don’t have a necessary condition for the museum’s remaining open, nor does the trustee confuse such a condition with a sufficient condition.
B
takes for granted that no previous exhibit at the museum had received such extensive media coverage
The trustee claims that media coverage likely helped boost this exhibit's record attendance, but he doesn't assume that no other exhibit has ever gotten as much media coverage.
C
takes for granted that most people who read articles about the exhibit also attended the exhibit
The trustee thinks that local media coverage contributed to the exhibit’s record-breaking attendance, but he doesn’t assume that most people who read articles about the exhibit also attended it. We don’t even know if the “local media” was in the form of articles at all.
D
fails to address the possibility that the exhibit would have drawn enough visitors to prevent bankruptcy even without media coverage
The exhibit might have had enough visitors to stay open even without media coverage. Just because the media coverage likely helped draw record attendance doesn’t mean that the exhibit would have had low attendance— and thus closed— without it.
E
presupposes the very conclusion that it is trying to prove
This is the cookie-cutter flaw of circular reasoning, where the author’s conclusion simply restates a premise. The trustee doesn’t make this mistake; his premises and conclusion are distinct.
This is a pretty tough question. We're prone to understand the argument incorrectly.
The conclusion states that the museum's continued existence depended on the coverage from the local media. In other words, the local media's coverage was a necessary condition for the museum's being still open and in business.
Fair enough. Why should we believe this? One premise says that if there was low attendance at the recent exhibit then the museum would have closed. Okay, good. This means that a necessary condition of the museum staying open is medium-to-high level attendance at the recent exhibit.
Now, in order for the conclusion to follow, we simply need to show that coverage from the local media was the only thing responsible for medium-to-high level attendance.
Does the remaining premises show that? No. It says that local media coverage existed. It also says that local media coverage seems to have contributed to attendance. In other words, it seems to have been a causal factor.
Seems to have contributed? Did it contribute or not? Was it a causal factor or not? We don't know.
That's mistake #1.
Correcting for it, the premise still isn't good enough. The corrected version says that local media coverage contributed to attendance. We we needed it to say that local media coverage was the necessary cause for medium-to-high level attendance. Otherwise, why would the museum's existence depend on it? That's mistake #2.
As for (A), the "necessary condition" it's referring to is "medium-to-high level attendance at the recent exhibit." But the argument never mistook that for a sufficient condition. Did you?
Economist: A tax is effective if it raises revenue and burdens all and only those persons targeted by the tax. A tax is ineffective, however, if it does not raise revenue and it costs a significant amount of money to enforce.
Summary
If a tax raises revenue and burdens only people targeted by the tax, then then tax is effective. If a tax does not raise revenue and it costs a significant amount of money to enforce, then the tax is ineffective.
Strongly Supported Conclusions
If a tax is ineffective, then it either does not raise revenue or it does not burden all and only people targeted by the tax.
A
The tax on cigarettes burdens most, but not all, of the people targeted by it. Thus, if it raises revenue, the tax is effective.
This answer is unsupported. This answer fails one of our sufficient conditions for a tax to be considered effective. We need both of the sufficient conditions in order for a tax to be considered effective.
B
The tax on alcohol raises a modest amount of revenue, but it costs a significant amount of money to enforce. Thus, the tax is ineffective.
This answer is unsupported. This answer fails one of our sufficient conditions for a tax to be considered ineffective. We need both of the sufficient conditions in order for a tax to be considered ineffective.
C
The tax on gasoline costs a significant amount of money to enforce. Thus, if it does not raise revenue, the tax is ineffective.
This answer is strongly supported. It meets both of our sufficient conditions we are given for a tax to be considered ineffective.
D
The tax on coal burdens all of the people targeted by it, and this tax does not burden anyone who is not targeted by it. Thus, the tax is effective.
This answer is unsupported. There are two sufficient conditions to be met in order for a tax to be considered effective. This answer only satisfies one of the two sufficient conditions.
E
The tax on steel does not cost a significant amount of money to enforce, but it does not raise revenue either. Thus, the tax is ineffective.
This answer is unsupported. This answer fails one of our sufficient conditions for a tax to be considered ineffective. We need both of the sufficient conditions in order for a tax to be considered ineffective.