Environmentalist: Pollution from gasoline burned by cars contributes to serious environmental problems. But the cost of these problems is not reflected in gasoline prices, and hence usually does not affect consumers’ decisions about how much to drive. Heavier taxes on gasoline, however, would reflect this cost, and as a result consumers would pollute less.

Summary

Pollution from gas burned by cars contributes to serious environmental problems. Gas prices do not reflect this environmental cost and so it usually doesn’t affect people’s decisions about how much to drive. Higher gas taxes would reflect the environmental cost and would cause people to pollute less.

Strongly Supported Conclusions

If gas prices increased, people would purchase less gas, and would thus reduce gas pollution.

Economic incentives can influence consumer decisions.

Some drivers’ decisions are not influenced by environmental costs.

A
The cost of pollution from driving should not be reflected in the price of gasoline unless the amount of pollution produced would be reduced as a result.

Unsupported. The stimulus does not claim that reduced pollution must occur in order to justify higher taxes on gasoline. Instead, it claims that increasing taxes on gas to reflect environmental cost would cause to people pollute less.

B
Heavier taxes on gasoline would increase consumers’ awareness of the kinds of environmental problems to which pollution from driving contributes.

Unsupported. Higher taxes on gas would cause people to pollute less, but we do not know that this is due to increased environmental awareness. Perhaps it is simply because gas prices are higher and so consumers can’t purchase as much gas as they did before.

C
Consumers would purchase less gasoline, on average, if the cost of the environmental problems to which pollution from driving contributes were fully reflected in the price of gasoline.

Strongly supported. Gas usage leads to pollution, and increasing the price of gas to reflect environmental cost would lead people to pollute less. So we can conclude that people would purchase less gas, on average, if gas prices increase.

D
The only cost considered by most consumers when they are deciding how much to drive is the cost of gasoline.

Unsupported. The cost of gas is a cost considered by most drivers when they are deciding how much to drive, but we do not know that it is the only cost.

E
Pollution from gasoline burned by cars will be reduced only if consumers give more consideration to the cost of that pollution when deciding how much to drive.

Unsupported. It is not necessary for consumers to consider the cost of pollution in order to reduce pollution from gas. If gas prices increase and consumers purchase less gas merely due to these taxes, gas pollution will still decrease.


15 comments

Hine’s emerald dragonflies are an endangered species that live in wetlands. The larvae of these dragonflies can survive only in the water, where they are subject to predation by several species including red devil crayfish. Surprisingly, the dragonfly populations are more likely to remain healthy in areas where red devil crayfish are present than in areas without red devil crayfish.

"Surprising" Phenomenon
Why are the dragonfly populations more likely to remain healthy in areas where red devil crayfish are present than in areas without red devil crayfish, even though the dragonfly larvae can survive only in water, and those larvae can be eaten by red devil crayfish when they are in water?

Objective
The correct answer should tell us something beneficial for the dragonflies from being in areas with the red devil crayfish, or something negative from being in areas without red devil crayfish.

A
Red devil crayfish dig chambers that remain filled with water even when the surrounding wetlands dry up.
This is a benefit for the dragonfly from being in areas with red devil crayfish. Without the water chambers created by the crayfish, larvae might not be able to survive. This may be why dragonfly populations are higher in areas with the crayfish despite the extra predation.
B
Red devil crayfish present no threat to adult Hine’s emerald dragonflies.
But the crayfish can still eat the dragonfly larvae. We’d still expect the dragonfly population to be better off without the red devil crayfish.
C
The varied diet of the red devil crayfish does not include any animal species that prey on dragonfly larvae.
If the crayfish eat the larvae, and don’t eat anything that preys on the larvae, that’s worse for the larvae. We’d expect the dragonfly population to be better off without the red devil crayfish.
D
Red devil crayfish are found in many more locations than Hine’s emerald dragonflies are.
The number of places the crayfish is found doesn’t tell us anything beneficial about the crayfish for the dragonfly population. We still don’t know why the dragonfly population is higher in areas with the crayfish than in areas without.
E
Populations of red devil crayfish in a wetland do not drop significantly if the local population of Hine’s emerald dragonflies dies out.
This suggests crayfish might eat other things besides the dragonflies. But they can still eat dragonfly larvae. So, we’d still expect the dragonfly population to be better off without the red devil crayfish.

15 comments

Stress is a common cause of high blood pressure. By calming their minds and thereby reducing stress, some people can lower their blood pressure. And most people can calm their minds, in turn, by engaging in exercise.

Summary
The stimulus says that stress often causes high blood pressure. Also, some people can calm their minds to lower their stress and thus reduce their blood pressure. Finally, most people can calm their minds by exercising.
In Lawgic, this looks like:
P1. calm mind -s→ lower stress -s→ lower BP
P2. exercise -m→ calm mind

Strongly Supported Conclusions
The stimulus supports the conclusion that some people can probably use exercise to lower their blood pressure.
In Lawgic, this means combining the premises listed above to look like:
P1. exercise -m→ calm mind -s→ lower stress -s→ lower BP

A
For at least some people, having lower blood pressure has at least some tendency to cause their stress levels to be reduced.
This is not supported. The stimulus tells us about a causal link where high stress can cause high blood pressure, not the other way around.
B
Most people with high blood pressure can lower their blood pressure by reducing their stress levels.
This is not supported. Reading closely, the stimulus only says that stress is a “common” cause of high blood pressure. “Common” doesn’t equate to “most.” Instead, it would be better translated as “some,” which does not support this inference.
C
Most people who do not exercise regularly have higher stress levels as a result.
This is not supported. Firstly, most people can calm their minds by exercising, but a calm mind only sometimes reduces stress—maybe less than half the time, we don’t know. Secondly, there may be other ways to calm the mind and reduce stress without exercising.
D
Engaging in exercise can directly lower one’s blood pressure.
This is not supported. The stimulus describes a very indirect mechanism for exercise to sometimes lower blood pressure: we need the intermediate steps of calm mind and stress reduction first. That’s definitely not a direct link between exercise and lower blood pressure.
E
For at least some people, engaging in exercise can cause their stress levels to be reduced.
This is strongly supported. Based on the stimulus, exercise can calm the mind, which can reduce stress, which can reduce blood pressure. None of these steps is guaranteed, but it seems very likely that at least some people make it all the way to lower blood pressure.

9 comments

A positive correlation has been found between the amount of soot in the atmosphere of cities and the frequency of a certain ailment among those cities’ populations. However, the soot itself probably does not cause this ailment, since in cities where there are large amounts of soot in the air, there are usually also high concentrations of many other air pollutants.

Summarize Argument
The author concludes that soot itself doesn’t cause a certain ailment. This is because cities with lots of soot in the air usally also have lots of other pollutants in the air.

Notable Assumptions
The author assumes that the ailment in question isn’t specifically linked to soot and not linked to other pollutants. If this were the case, then soot could likely be identified as a cause of the ailment. The author also assumes that the ailment isn’t prevalent in places where there’s soot in the air but no other pollutants. The author claims soot is usually accompanied by other pollutants, which means there are instances where this isn’t the case.

A
In cities where there are high concentrations of many air pollutants but little if any soot in the air, the frequency of the ailment is just as high, on average, as it is in cities where there are large amounts of soot in the air.
This supports the author’s argument. Other pollutants are likely causing the ailment.
B
If the ailment rarely occurs except in cities in which there are large amounts of soot in the air, then the soot is probably the cause of the ailment.
Does this ever happen? We don’t know.
C
In each of the cities where there are large amounts of soot in the air but little other air pollution, the frequency of the ailment is at least as high as it is anywhere else.
When soot and no other pollutants are in the air, the ailment is as prevalent as ever. Thus, soot seems likely to be the cause of the ailment.
D
If high concentrations of many different pollutants in a city’s air are correlated with a high frequency of the ailment among that city’s population, then it is possible that two or more of those pollutants each causally contributes to the ailment.
This seems to support the author’s argument. Several of the pollutants together could’ve cause the ailment, rather than soot alone.
E
In cities in which there are high concentrations of many air pollutants, there are generally also high concentrations of other forms of pollution that are very likely to contribute causally to the ailment.
This supports the author’s argument. Other forms of pollution are contributing to the ailment rather than soot alone.

25 comments