#22 - Researchers have found that children in large families

[Administrator]

Complete Question Explanation

Strengthen, CE. The correct answer choice is (E)

The researchers’ argument is structured as follows:

• Premise: Children in large families—particularly the younger siblings—generally have fewer allergies than children in small families do.
  
  Conclusion: Exposure to germs during infancy makes people less likely to develop allergies.

In other words, the researchers compared the incidence of allergies in large families vs. small families, and found that the younger siblings in large families have a lower risk of developing allergies than children in small families. They conclude that it is exposure to germs during infancy that makes people less likely to develop allergies. Because the conclusion seeks to explain an observation presented in the premise, the relationship between premise and conclusion is a causal one, and can be diagrammed as follows:

• Lower Allergy Risk = Younger siblings in large families have a lower risk of developing allergies than children in small families
  
  Germs While Young = Exposure to germs during infancy

Cause Effect

Germs While Young Lower Allergy Risk

Although the argument proceeds in a predictable fashion (the premise presents a phenomenon; the conclusion attempts to explain it), this is a challenging question due to the convoluted causality underlying the researchers’ hypothesis. In order to strengthen it, you first need to understand why exposure to germs during infancy is reasonable explanation for the comparatively low incidence of allergies among younger siblings in large families.

The logic is as follows: the more people we come in contact with, the more germs we are exposed to. Hence, children raised in large families are typically exposed to more germs by their siblings than children raised in small families. Likewise, younger siblings in large families are exposed to more germs during their infancy than their older siblings were (the elders grew up in a family whose size was smaller). It turns out that the younger siblings in large families—the ones with the greatest exposure to germs during infancy—also have the fewest allergies. On the basis of this correlation, the researchers concluded that there is a causal relationship between exposure to germs during infancy and the likelihood of developing allergies.

Correlations between two variables do not automatically imply that one causes the other, as they may be coincidental effects of another cause. For instance, what if younger siblings in large families tend to eat less allergenic foods than their older siblings? This would explain why they have fewer allergies. Also, what if small families were more common in industrialized countries, where environmental pollutants play a greater role in the development of allergies than in less industrialized countries?

To strengthen the argument, look for answers that either eliminate such alternate causes, or show an analogous case in which the cause occurs (exposure to germs), and the effect also occurs (lower allergy risk). You can also support the cause and effect relationship by showing that when the cause does not occur, the effect does not occur.

Answer choice (A): This answer choice may seem attractive, because it provides further evidence of the negative association between family size and the incidence of developing allergies. However, we have no proof that the increased incidence of allergies in countries where the average number of children per family has decreased affected the younger siblings in those families. If it did not, the increased incidence of allergies may have been caused by something other than the decreased exposure to germs.

Furthermore, we need to take into account the incidence of allergies in countries where the average number of children per family did not decrease. If children in such countries also had an increased risk of developing allergies, then clearly something other than family size (and germ exposure) must have elevated the risk in both types of countries. Since this answer choice does not present a clear comparison, it is impossible to evaluate its effect on the conclusion of the argument.

Answer choice (B): This Opposite answer presents an alternate cause for the increased incidence of allergies. If children in small families eat more kinds of very allergenic foods than children in large families do, this would explain why the likelihood of developing allergies varies by family size.

Answer choice (C): This answer choice does not address the causal relationship between family size and the incidence of allergies. The question stem does not ask you to justify exposure of children to germs in order to prevent allergy.

Answer choice (D): This Opposite answer suggests that an alternate cause may affect the incidence of allergies: if children whose parents have allergies have an above-average likelihood of developing allergies themselves, then susceptibility to allergies would be hereditary. In that case, the chance of developing allergies would be determined at birth. This is clearly at odds with the premise that younger siblings in large families have fewer allergies than older siblings, and weakens the conclusion that an environmental factor (such as exposure to germs) makes people less likely to develop allergies.

Answer choice (E): This is the correct answer choice. If children from small families who entered day care before age one were less likely to develop allergies than children from small families who entered day care later, this provides additional evidence to support the hypothesis that exposure to other children (and therefore germs) leads to a decreased incidence of allergies. Note that this answer choice correctly compares the incidence of allergies in children from the same family size, which helps eliminate any potential biases inherent in the original study. Because early germ exposure via day care cohorts (as opposed to older siblings) results in the same decreased incidences of allergies, this answer choice presents an analogous case in which the cause occurs, and the effect occurs.

[lsat2016]

I found that A is wrong is because the stimulus is specific to children while the answer choice says "allergies has increased", which can refer both to adults and children.

However, is another a possible reason why A is wrong because the stimulus points to a causal relationship (exposure to germs CAUSE people to less likely develop allergies) while the answer choice points to a correlational relationship? I just wanted to confirm whether this is a valid reason for eliminating an answer choice.

Thank you

[Shannon Parker]

Hey there,

Good question. Yes. This is a classic cause and effect question, and the absence of causal reasoning in the answer choice definitely weakens, as does the fact that the increase in allergies referred to in the answer choice is not specific to children while the increase in the stimulus is. You always want to make sure that your stimulus and answer choice match up. Good catch.

-Shannon

[kcho10]

I can see why E is the best answer, but it still seems very flawed to me. I don't see how we can assume that more people=more germs. Maybe the day care is very conscious of how clean it is. There could be so many other reasons to explain why more people in families/day cares led to less cases of allergies. Also, the passage doesn't relate large families to germs- the passage seems to assume this in the argument. E seems to just assume that assumption as well.

I can see how E is still better than A, but I wanted to make sure that the flaws I saw are correct. Please let me know if I am missing something. Thank you

[Adam Tyson]

You're right, kcho - the author here HAS made an assumption that more people = more germs, and that assumption could surely be challenged in a Flaw question or exposed in an Assumption question. The issue here, though, is not whether answer E is a perfect answer (it isn't), but whether it is the best answer of the five choices presented (and it is). It is not unreasonable to believe, and our test authors may have taken it as common knowledge, that more people means a larger number and greater variety of germs. Perhaps they are somewhat unfairly tasking us with bringing in outside information, but it's not much of a stretch. It also takes outside information to say that if the sun is shining it must be daytime, but that's reasonable too, even if it could be shining in mid-summer at midnight at the North Pole, or at the International Space Station or at the NSA's top secret moon base from which they are constantly watching us (you knew that, right?)

Don't get caught up in the trap of looking for perfect answers, or even for good ones. Look for the ones that are better than the other four, no matter how bad they might be, and pick those without fear or hesitation. You said it yourself - "I can see why E is the best answer" - and that is all you need to find on this test. Anything more is a fun intellectual exercise that you can go through AFTER you get your amazingly high score and a copy of the test back a few weeks after the fact!

Pick the best one, no matter how bad it may be. Good luck!

[akanshalsat]

Hello! I still don't understand why A is wrong... You say it's because we don't have proof for that, but in strengthen questions, we are allowed to say that the answer choices can be taken as true right?, moreover, E doesn't say anything about large vs small families... is that b/c it doesn't matter since the size of the family was discussed in the premise, and we are supposed to strengthen the conclusion?

[Adam Tyson]

Allow me to clarify our official response for you, akanshalsat. We aren't saying that we have no proof that the answer is true - we don't need proof of that, because in a strengthen question we are just supposed to accept it as true. What we are saying is that even if it is true that a decreased average family size coincides with an increased incidence of allergies, that answer tells us nothing about the youngest children in those families. Are they getting more allergies, or is their incidence still low? If the younger kids are being exposed to their older siblings and yet getting more allergies, that would weaken the argument that exposure in infancy is causing resistance to allergies by suggesting that there may be another cause at work. If, on the other hand, the younger kids in multi-child families are still developing a resistance to allergies, that would perhaps help. The problem is that this answer leaves us wondering about that important element, the younger siblings.

Remember, the argument isn't just "bigger families mean fewer allergies". It's "exposure to more germs when young reduces allergies". Answer E gives us that in a different setting, outside the large families. Kids going to daycare young are exposed to more germs (the cause is present) and developing fewer allergies (the effect is present), and that helps.

[cornflakes]

Hi Powerscore,

I eliminated A because it doesn't actually address the hypothesis' claims regarding exposure to germs "infancy". It does strengthen the premise/background info of smaller family meaning more allergies to some degree, but it doesn't provide any information regarding this infancy versus non-infancy idea.

I think the reason why A was attractive for a while is because in the prephrase, I and probably many people were expecting to see in answer involving discrepancies in family size used in some comparative nature or manner. E does qualify its comments as applying to "small families", but its primarily interested in demonstrating the difference in outcomes when exposing children to germs in infancy versus exposing them after infancy (aka not in infancy). Because the children under the age of 1 (infancy) developed fewer allergies, this alone proves the hypothesis - whether those children derive from a small family, large family, or whatever, seems less relevant.

[Adam Tyson]

Agreed with one caveat, cornflakes, and that is that the correct answer doesn't prove the conclusion. It helps (strengthens), but is not strong enough to prove (justify). There still could be other causes for the correlation observed. Other than that, good analysis!

[ashpine17]

Could someone check my reasoning as to why answer choice A is incorrect? A states that in countries where the average number of children has decreased, the incidence of allergies has increased; does this correlation not necessarily impact the causal relationship in the stimulus between exposure to bacteria and incidence of allergies since they might be unrelated and not impact the incidence of allergies among siblings in families? Maybe the overall incidence of allergies in the country declined but it stayed the same or even increased among younger siblings in larger families?