Dr. Snow

[success1111]

Learning how to build a nest plays an important part in the breeding success of birds. For example, Dr. Snow has recorded the success of a number of blackbirds in several successive years. He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. This cannot be a mere matter of size and strength, since blackbirds, like the great majority of birds, are fully grown when they leave the nest. it is difficult to avoid the conclusion that they benefit by their nesting experience.

Which one of the following, if true, would most weaken the argument?

(A) Blackbirds build better nests than other birds.

(B) The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction.

(C) The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time.

(D) Smaller and weaker blackbirds breed just as successfully as bigger and stronger blackbirds

(E) Up to 25 percent of all birds are killed by predators before they start to nest

[effective_factor]

Learning how to build a nest plays an important part in the breeding success of birds. For example, Dr. Snow has recorded the success of a number of blackbirds in several successive years. He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. This cannot be a mere matter of size and strength, since blackbirds, like the great majority of birds, are fully grown when they leave the nest. it is difficult to avoid the conclusion that they benefit by their nesting experience.

Which one of the following, if true, would most weaken the argument?

(A) Blackbirds build better nests than other birds.

(B) The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction.

(C) The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time.

(D) Smaller and weaker blackbirds breed just as successfully as bigger and stronger blackbirds

(E) Up to 25 percent of all birds are k!IIed by predators before they start to nest

IMO B

A we are talking about blackbirds and we are not comparing them with other birds this option has no impact on the argument

C this option not truely weakens the argument as its written that
He finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later.
C only talks about first two years

D tries to contradict the premise but it doesnt contradict the conclusion that nesting plays a role

E is irrelevant

B is best as it states the nesting isn't the main reason its their hit and trial of reproducing

[yashanth.ponnanna]

"B" is the best answer!!

[success1111]

"B" is the best answer!!

OA is B.

[shekhar.kataria]

Can anyone please put some light on why D is wrong.

[rkanthilal]

Can anyone please put some light on why D is wrong.

Hi shekhar.kataria,

Regarding answer D:

The argument specifically states that breeding success "cannot be a mere matter of size and strength." The fact that smaller and weaker birds breed just as successfully as bigger and stronger birds is consistent with the argument and therefore doesn't weaken it.

[shekhar.kataria]

Can anyone please put some light on why D is wrong.

Hi shekhar.kataria,

Regarding answer D:

The argument specifically states that breeding success "cannot be a mere matter of size and strength." The fact that smaller and weaker birds breed just as successfully as bigger and stronger birds is consistent with the argument and therefore doesn't weaken it.

Thanks Rkanthilal

[samudranb]

Can anyone please put some light on why D is wrong.

Hi shekhar.kataria,

Regarding answer D:

The argument specifically states that breeding success "cannot be a mere matter of size and strength." The fact that smaller and weaker birds breed just as successfully as bigger and stronger birds is consistent with the argument and therefore doesn't weaken it.

In fact, it strengthens it.

[TheGraduate]

The Official Answer is (B). However, what I don't understand is that doesn't B say the same thing that is stated in the stimulus? That is, nesting experience is the cause of breeding breeding success. In my opinion, "each successive trial during the first few years of production" in option B ought to express the same idea as "nesting experience" in the stimulus.
Also, in my opinion, "capacity of blackbirds to lay viable eggs" ought to express the same idea as "breeding success".

[MBA Challengers]

Hi,

Just to put the question into context, looking at it through Premises and Conclusion:

Conclusion: Learning how to build a nest (nesting) plays an important part in the breeding success of birds

Premise 1: Black birds nesting for first time less successful than older birds and themselves also in the next year
Premise 2: This is not a matter of size or strength as most blackbirds are fully grown when they leave the nest

Checking for the options:
A. The example is comparing within the blackbird species. INCORRECT
B. This option gives an alternate reason for the breeding success of blackbirds in later years - it talks about how the egg-laying capacity improves with successive breeding season. This option negates the idea of nesting or the ability of building a nest being the primary factor of the success of the blackbird's breeding season. CORRECT
C. This is in some ways strengthening the conclusion talking about birds as a larger category and the observation that they are more successful at breeding in the second season, rather than the first. INCORRECT.
D. The conclusion in consideration is about nesting and not about size as that is already dealt with in the 2nd premise. INCORRECT.
E. This has nothing at all to do with any of the information given in the passage. INCORRECT

Thus, the correct answer is B.

[TheGraduate]

Hi,

Just to put the question into context, looking at it through Premises and Conclusion:

Conclusion: Learning how to build a nest (nesting) plays an important part in the breeding success of birds

Premise 1: Black birds nesting for first time less successful than older birds and themselves also in the next year
Premise 2: This is not a matter of size or strength as most blackbirds are fully grown when they leave the nest

Checking for the options:
A. The example is comparing within the blackbird species. INCORRECT
B. This option gives an alternate reason for the breeding success of blackbirds in later years - it talks about how the egg-laying capacity improves with successive breeding season. This option negates the idea of nesting or the ability of building a nest being the primary factor of the success of the blackbird's breeding season. CORRECT
C. This is in some ways strengthening the conclusion talking about birds as a larger category and the observation that they are more successful at breeding in the second season, rather than the first. INCORRECT.
D. The conclusion in consideration is about nesting and not about size as that is already dealt with in the 2nd premise. INCORRECT.
E. This has nothing at all to do with any of the information given in the passage. INCORRECT

Thus, the correct answer is B.

Yeah. But my question is a bit different. I'm wondering if "successive trial" itself refers to "nesting experience". In other words I need an elaboration of the interpretation of the second part of the answer choice. i.e. The capacity of of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction.

[MBA Challengers]

Hi TheGraduate,

What the option implies is that the the birds' egg laying capacity improves with each successive breeding season (trial). Essentially, breeding season is seen as comprising of nesting (nest-making ability) and egg-laying ability. In the question stem, the author has assumed that the success of the breeding season for a bird depends on his nesting ability. However, this option adds enough doubt with the premise that even the egg laying ability could be improving with each successive trial/breeding season leading to its' success or failure. Thus, this option provides ample doubt to weaken the conclusion.

Hope this clears your doubt.

[TheGraduate]

Hi TheGraduate,

What the option implies is that the the birds' egg laying capacity improves with each successive breeding season (trial). Essentially, breeding season is seen as comprising of nesting (nest-making ability) and egg-laying ability. In the question stem, the author has assumed that the success of the breeding season for a bird depends on his nesting ability. However, this option adds enough doubt with the premise that even the egg laying ability could be improving with each successive trial/breeding season leading to its' success or failure. Thus, this option provides ample doubt to weaken the conclusion.

Hope this clears your doubt.

I still have a bit of a doubt though. As far as I get it, the causality provided in the stimulus goes as follows:
(increase in nesting experience over successive trials/seasons) --> (success in breeding)

Option B: (increase in nesting experience over successive trials/seasons) --> (increase in capacity to lay viable eggs)

I fail to understand the gap (increase in capacity to lay viable eggs) and (success in breeding).
Shouldn't (increase in capacity to lay viable eggs) equate to (success in breeding) ?

[MBA Challengers]

Hi,

Breeding is the ability to find a mate in the mating season.

To understand the question better imagine this:

According to the author in the question stem, in the blackbird community, they know that if the bird has just started breeding, its' nest-making ability or nesting will not be that great so there will be not too many takers for it in the breeding season. But gradually after a few seasons have passed its' nest making abilities will be known to be better which will also mean better takers for it in the breeding season.

However option B opines that in the blackbird society when they know that a bird has just started breeding they know it's not great shakes at laying eggs yet and maybe still an apprentice. However, with a few years under their belt, other birds in the society will know that this is a more experienced bird with better egg-laying ability. This will mean a better breeding season for that bird and more and better mating possibilities.

[GMATGuruNY]

The Official Answer is (B). However, what I don't understand is that doesn't B say the same thing that is stated in the stimulus? That is, nesting experience is the cause of breeding breeding success. In my opinion, "each successive trial during the first few years of production" in option B ought to express the same idea as "nesting experience" in the stimulus.
Also, in my opinion, "capacity of blackbirds to lay viable eggs" ought to express the same idea as "breeding success".

This CR attempts to link the ability to BUILD A NEST with the ability to BREED.
To weaken the conclusion, the correct answer must break this link.
B: The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction.
This option indicates that blackbirds become better breeders after MULTIPLE ATTEMPTS, regardless of their ability to build a nest.
According to B, even a blackbird in a laboratory -- where the building of a nest is unnecessary -- will become a better breeder after multiple attempts.
Thus, B breaks the link between the ability to build a nest and the ability to breed, WEAKENING the conclusion that nest-building was responsible for the breeding success of the blackbirds studied by Dr. Snow.