It is widely believed that lancelets—small, primitive sea animals—do not have hearts. Each lancelet has a contracting vessel, but this vessel is considered an artery rather than a heart. However, this vessel is indeed a heart. After all, it strongly resembles the structure of the heart of certain other sea animals. Moreover, the muscular contractions in the lancelet’s vessel closely resemble the muscular contractions of other animals’ hearts.

Summary
The author concludes that lancelets have hearts, because they have a vessel that is similar to other hearts in their structure and contractions.

Missing Connection
The conclusion is about having a heart, but we aren’t given information on what qualifies as having a heart. The support only comes from the structure and behavior of the lancelet’s vessel bearing similarity to other hearts. We can make the argument valid if we know for sure that one or both of these qualities (structure or behavior) having commonality with other hearts is enough to qualify as having a heart.

A
Only animals that have contracting vessels have hearts.
This is switching sufficient and necessary. (A) can only support a conclusion about having contracting vessels or, through contrapositive, not having a heart. We need something that would support a conclusion about having a heart.
B
Some primitive animals other than lancelets have what is widely held to be a heart.
Irrelevant. Just because other animals with one similarity to the lancelet have a heart, it does not strengthen the argument that lancelets have a heart. Even in a Strengthen question, this answer is problematic.
C
A vessel whose structure and actions closely resemble those of other animal hearts is a heart.
This links the vessel of the lancelet to a conclusion about having a heart. This means the traits of the lancelet’s vessel qualify for having a heart.
D
For a vessel in an animal to be properly considered a heart, that vessel must undergo muscular contractions.
Similar to (A), a reversal of what we need. We need for “properly considered a heart” to be a necessary condition. We need to conclude that something has a heart, and we cannot do that when it is in the sufficient condition.
E
No animal that has a heart lacks an artery.
Phrased another way, this is “If an animal has a heart, then it has an artery.” This has the same issue as (A) and (D)— We need to conclude that something has a heart, and we cannot do that when it is in the sufficient condition.

3 comments

Manager: I recommend that our company reconsider the decision to completely abandon our allegedly difficult-to-use computer software and replace it companywide with a new software package advertised as more flexible and easier to use. Several other companies in our region officially replaced the software we currently use with the new package, and while their employees can all use the new software, unofficially many continue to use their former software as much as possible.

Summary

The manager recommends that the company reconsider the decision to replace current software with a new software package. This is because several other companies in the region have done such replacement, but many employees at these companies continue to use their old software as much as possible.

Strongly Supported Conclusions

Many employees at the manager’s company would probably continue to use the now-current software if it is replaced by the new software package.

The advantages of the new software package are unlikely to compel every employee to use it over the now-current software.

A
The current company software is as flexible as the proposed new software package.

Unsupported. The stimulus doesn’t tell us the flexibility of the current software or how it compares to the flexibility of the new software package.

B
The familiarity that employees have with a computer software package is a more important consideration in selecting software than flexibility or initial ease of use.

Unsupported. Although the manager suggests many will continue to use the current software, that could be due to its flexibility or ease of use. The new software is “advertised” as more flexible, but that doesn’t mean it is more flexible.

C
The employees of the manager’s company would find that the new software package lacks some of the capabilities of the present software.

Unsupported. Although the manager suggests many will continue to use the current software, we don’t know whether this will be due to any difference in capabilities of the software. It could be due to greater familiarity with current software.

D
Adopting the new software package would create two classes of employees, those who can use it and those who cannot.

Unsupported. There’s no indication that anyone will be unable to use the new software. Many will likely prefer to use the current software, but that doesn’t imply they lack the ability to use the new software.

E
Many of the employees in the manager’s company would not prefer the new software package to the software currently in use.

Strongly supported. The manager cites to the fact many employees from other companies chose to use their old software instead of the new software. The manager uses this to suggest that a similar phenomenon will occur at the manager’s company.


46 comments

Art historian: More than any other genre of representational painting, still-life painting lends itself naturally to art whose goal is the artist’s self-expression, rather than merely the reflection of a preexisting external reality. This is because in still-life painting, the artist invariably chooses, modifies, and arranges the objects to be painted. Thus, the artist has considerably more control over the composition and subject of a still-life painting than over those of a landscape painting or portrait, for example.

Summary

Compared to other kinds of representational painting, still-life painting lends itself more naturally to art whose goal is self-expression. This is because in still-life painting, the artist always chooses, modifies, and arranges the objects to be painted, which gives the artist more control over the composition and subject of the painting than the artist would have with other kinds of representational painting.

Strongly Supported Conclusions

In other kinds of representational painting besides still-life, the artists does not always choose, modify, or arrange the objects to be painted.

The level of control an artist has over the composition and subject of a painting is relevant to whether a style of painting lends itself naturally to self-expression.

A
Landscape painting and portraiture are the artistic genres that lend themselves most naturally to the mere reflection of a preexisting external reality.

Unsupported. We’re not told whether landscape and portraiture lend themselves most to anything. Perhaps there are other kinds of representational painting that lend themselves even more to reflecting preexisting reality.

B
The only way in which artists control the composition and subject of a painting is by choosing, modifying, and arranging the objects to be represented in that painting.

Unsupported. Choosing, modifying, and arranging the objects represented is one way that artists can exercise control, but we’re not told that it’s the only way.

C
Nonrepresentational painting does not lend itself as naturally as still-life painting does to the goal of the artist’s self-expression.

Unsupported. The stimulus doesn’t say anything about nonrepresentational painting. (Landscape and portrait painting are representational.)

D
In genres of representational painting other than still-life painting, the artist does not always choose, modify, and arrange the objects to be painted.

Strongly supported. The fact artists can choose/modify/arrange objects gives the artist more control over a still-life painting than other kinds of representational painting. This implies that in other kinds of repres. painting, the artist doesn’t always choose/modify/arrange.

E
When painting a portrait, artists rarely attempt to express themselves through the choice, modification, or arrangement of the background elements against which the subject of the portrait is painted.

Unsupported. We’re told that in still-life, the artist always chooses/modifies/arranges the objects to be painted. This still allows for the artist to choose/modify/arrange in portrait painting, as long as the artist does not always have the ability to do so.


15 comments

Many vaccines create immunity to viral diseases by introducing a certain portion of the disease-causing virus’s outer coating into the body. Exposure to that part of a virus is as effective as exposure to the whole virus in stimulating production of antibodies that will subsequently recognize and kill the whole virus. To create a successful vaccine of this type, doctors must first isolate in the disease-causing virus a portion that stimulates antibody production. Now that a suitable portion of the virus that causes hepatitis E has been isolated, doctors claim they can produce a vaccine that will produce permanent immunity to that disease.

Summarize Argument
Doctors claim that they can create a vaccine providing permanent immunity to hepatitis E. This is because a suitable portion of the virus behind hepatitis E has been isolated, which is necessary for creating a vaccine.

Notable Assumptions
The doctors assume that isolating the virus behind hepatitis E is sufficient for creating a vaccine providing permanent immunity to the disease. This means the doctors don’t believe other relevant factors will pose significant challenges towards creating the vaccine, and that any given vaccine can actually provide “permanent immunity.”

A
Most of the people who contract hepatitis E are young adults who were probably exposed to the virus in childhood also.
People who contract hepatitis E have already been exposed to the virus, which means they should’ve gained the benefits the vaccine would provide. They evidently haven’t gained that benefit, which suggests the vaccine is unlikely to provide “permanent immunity.”
B
Some laboratory animals exposed to one strain of the hepatitis virus developed immunity to all strains of the virus.
The doctors never make claims about different strains of hepatitis.
C
Researchers developed a successful vaccine for another strain of hepatitis, hepatitis B, after first isolating the virus that causes it.
Hepatitis vaccines can indeed be developed from isolated viruses. If anything, this supports the doctors’ claim.
D
The virus that causes hepatitis E is very common in some areas, so the number of people exposed to that virus is likely to be quite high in those areas.
We don’t care how widespread the virus is. We only care whether a vaccine can be produced from the isolated virus.
E
Many children who are exposed to viruses that cause childhood diseases such as chicken pox never develop those diseases.
Since vaccines are just exposure to viruses, all this tells us is that vaccines seem to work.

23 comments

Columnist: The failure of bicyclists to obey traffic regulations is a causal factor in more than one quarter of the traffic accidents involving bicycles. Since inadequate bicycle safety equipment is also a factor in more than a quarter of such accidents, bicyclists are at least partially responsible for more than half of the traffic accidents involving bicycles.

Summarize Argument

The columnist concludes that bicyclists are partly responsible for more than half of all bike-related traffic accidents. She supports this by saying that bikers not following traffic rules contributes to more than a quarter of these accidents, and poor bike safety equipment is also a factor in more than a quarter of these accidents.

Identify and Describe Flaw

The columnist concludes that bicyclists are partly to blame for over half of bike-related accidents because two factors— not following traffic rules and using poor safety equipment— each contribute to more than a quarter of these accidents. Her reasoning is flawed because she assumes that these factors never overlap, or that only one factor contributes to each accident. But if some of these accidents involve both factors, she can't claim that bicyclists are responsible for over half of them.

A
presumes, without providing justification, that motorists are a factor in less than half of the traffic accidents involving bicycles

The columnist doesn’t address motorists or assume that they’re a factor in less than half of the accidents. She says bicyclists are at least partially responsible for more than half of the accidents, so motorists could be partially responsible for these accidents as well.

B
improperly infers the presence of a causal connection on the basis of a correlation

The columnist doesn’t draw a causal conclusion based on a mere correlation. Instead, she infers a detail about a causal relationship on the basis of a premise that does establish something as “a causal factor.”

C
fails to consider the possibility that more than one factor may contribute to a given accident

The columnist assumes that only one of the factors contributes to each accident. But if not following traffic rules and using poor safety equipment both contribute to some accidents, then it might not be true that bicyclists are partly responsible for over half of the accidents.

D
fails to provide the source of the figures it cites

The columnist doesn’t provide sources for her cited figures, but this isn’t a flaw in her reasoning.

E
fails to consider that the severity of injuries to bicyclists from traffic accidents can vary widely

The columnist’s argument is about the factors that contribute to bike-related traffic accidents. The severity of the bicyclists’ injuries from each accident is irrelevant.


19 comments

The law of the city of Weston regarding contributions to mayoral campaigns is as follows: all contributions to these campaigns in excess of $100 made by nonresidents of Weston who are not former residents of Weston must be registered with the city council. Brimley’s mayoral campaign clearly complied with this law since it accepted contributions only from residents and former residents of Weston.

Summary
The stimulus can be diagrammed as follows:

Notable Valid Inferences
Any contribution of $100 or less doesn’t have to be registered with the city council.
Any contribution made by a resident of Weston doesn’t have to be registered with the city council.
Any contribution made by a former resident of Weston doesn’t have to be registered with the city council.

A
No nonresident of Weston contributed in excess of $100 to Brimley’s campaign.
Could be false. Maybe a former resident of Weston contributed in excess of $100 to Brimley’s campaign.
B
Some contributions to Brimley’s campaign in excess of $100 were registered with the city council.
Could be true. The stimulus tells us that contributions over $100 don’t have to be registered with the city council as long they were made by a current or former Weston resident, but it doesn’t tell us that such donations can’t be registered by choice.
C
No contributions to Brimley’s campaign needed to be registered with the city council.
No contributions to Brimley’s campaign were made by someone who has never lived in Weston, so none of the contributions fall into the category of donations that need to be registered with the city council.
D
All contributions to Brimley’s campaign that were registered with the city council were in excess of $100.
Could be true. Maybe each of the current and former residents that contributed to Brimley’s campaign donated more than $100.
E
Brimley’s campaign did not register any contributions with the city council.
Could be true. We know that Brimley’s campaign were not required to register any contributions with the city council, and they may have decided not to.

This question's pretty tough so I hope you didn't spend too much time on it.

The stimulus tells us that "the law" is as follows. It's important for (C) to note that in context, we are to presume that this is the only law that pertains to contributions to mayoral campaigns in Weston.

What's "the law"?
If (1) $100+ and (2) currently nonresident and (3) never was a resident then must be registered.

For Brimley's campaign, we know that (4) he complied with this law and (5) accepted contributions from residents and former residents and no one else.

What must be true? (4) tells us that his campaign did not run afoul of the law (in other words, no contradiction). We overlook this fact because (4) is a conclusion and we're well trained to be skeptical of conclusions. But, this is a MBT question. The question stem explicitly tells us to presume that EVERYTHING in the stimulus is true. We must accept that in fact Brimley's campaign was run legally.

(5) tells us that Brimley's campaign failed the sufficient conditions of the law. Remember logic games lessons? Sufficient failed, rule irrelevant. In context, that means Brimley's campaign did not have to register any of its contributions. That's exactly what (C) says.

(A) is the attractive, trap answer choice. We're thinking, well, (A) must be true right?

If nonresidents contributed in excess of $100, then it would have to be registered.

First, that's false. This is true: if nonresidents who were never residents contributed in excess of $100, then it would have to be registered. See the difference?

Second, even if that's not false, we don't actually know if Brimely's campaign registered any contributions. We know that (C) they did not NEED to register. But maybe they registered for fun anyway.


58 comments

City council member: The Senior Guild has asked for a temporary exception to the ordinance prohibiting automobiles in municipal parks. Their case does appear to deserve the exception. However, if we grant this exception, we will find ourselves granting many other exceptions to this ordinance, some of which will be undeserved. Before long, we will be granting exceptions to all manner of other city ordinances. If we are to prevent anarchy in our city, we must deny the Senior Guild’s request.

Summarize Argument
The council member concludes that to prevent anarchy, the council must deny the Senior Guild’s request for an exception. As support, he says that granting this exception would lead to other, undeserved exceptions and eventually to exceptions to all kinds of city ordinances.

Identify and Describe Flaw
The council member’s argument is vulnerable to criticism because he never provides evidence to support the key assumption that granting the Senior Guild’s exception would inevitably cause the council to grant undeserved exceptions to all kinds of city ordinances. Similarly, he never gives reason to believe that granting the request would cause anarchy.

A
distorts an argument and then attacks this distorted argument
The council member never attacks, distorts, or even presents any argument made by the Senior Guild. Instead, he presents his own argument for why the Guild’s exception should be denied.
B
dismisses a claim because of its source rather than because of its content
This is the cookie-cutter “ad hominem” flaw. The council member doesn’t make this mistake. He argues that the Guild’s request should be denied, but he doesn’t do so by attacking the Guild itself. In fact, he concedes that the Guild deserves this exception.
C
presumes, without sufficient warrant, that one event will lead to a particular causal sequence of events
The council member assumes that granting the Senior Guild’s exception will lead to a particular causal sequence of events— all manner of other exceptions and anarchy. But he doesn't offer any reason to think that one will actually cause the other.
D
contains premises that contradict one another
The council member’s premises may not support his conclusion well, but they never contradict one another.
E
fails to make a needed distinction between deserved exceptions and undeserved ones
The council member actually does distinguish between undeserved and deserved exceptions by pointing out that the Senior Guild’s exception is deserved, while some others are not. He just fails to take that distinction into consideration in his argument.

7 comments