Q19 - Birds need so much food

[clarafok]

hello

i spent 10 minutes staring at C and D trying to figure out which one it was and i ended up going with D.

i thought we needed an assumption to explain the gap that seed-eating birds spend more time eating than nectar-eating birds because nectar has more energy than seeds.

i thought D would fill the gap because if seed-eating birds have lower body temperatures, then they would need more energy to maintain it so it explains why they would spend more time eating. but i guess i fell into the LSAT trap because the argument states that they have the same overall energy requirement, so even if they need to use more energy to maintain their body temperature, it wouldn't imply that they would require more energy. is that right?

so, C is right because if they both have the same energy requirement, and if nectar has more energy, then of course the nectar-eating birds would spend less time eating.

can someone tell me if my logic is correct?

thanks in advance!

[bbirdwell]

This logic is correct. Sounds like you fell into imaginative interpretation mode when looking at this one instead of staying in analysis mode! Remember that -- analyze, don't interpret.

[romanmuffin]

I'm still a bit shaky on this one. I kind of see why C is correct but I chose B. Doesn't the negation of B hurt the argument? If nectar-eating birds do sometimes also eat seeds, how can we can make a fair comparison in how long it takes for each bird to eat?

Where am I going wrong with this? I still don't really understand the explanation for C above. Can someone work through the answer choices?

[timmydoeslsat]

This argument has a core of:

Given amount of nectar gives more energy than same amount of seeds.

--->
Seed-eating birds spends more time eating than nectar-eating birds (Both with same energy requirements)


Does that conclusion necessarily follow? No.

What is the gap?

Try an analogous argument:

Given amount of tough shoe leather flank steak gives more energy than a bowl of soup.

---->
Person eating bowl of soup spends more time eating than person eating tough shoe leather flank steak.


This argument is assuming that eating the steak does not take longer to eat than the bowl of soup.

The argument in question is not considering the factor of how long it takes to eat those certain foods.

Answer choices:

A) Not necessary. The conclusion is talking about equal energy requirement birds of species.

B) Is not necessary as laid out by the premises to conclusion.

The conclusion is being reached on the idea of a given amount of nectar having more energy as the same amount of seeds.

C) Definitely necessary. Try negating it: If it is longer then you could not conclude that the comparison would show that species spends less time eating.

D) Does not matter. The energy requirements are the same, thus the body temperature is no longer a factor.

E) Even if it does depend on those listed factors, the argument is strictly about going from energy requirements...one type of food has more energy than other....therefore the one that has less energy will cause the species to spend more time eating it.

[geverett]

Still having a bit of trouble with C. I feel like the negation of it would have to assume that the longer time it takes to eat the given amount of nectar is not offset by the concomitant advantage of the increased amount of energy contained in the given amount of nectar.

What I mean is perhaps it take "longer". (How much longer who knows since the use of "longer" here is pretty ambiguous) but b/c the nectar provides more energy the increase in time is offset by the increase of energy provided by the given amount of nectar. I realize you would have to assume this, but that's why I had a hard time with this answer choice b/c it seems you would have to insert an assumption either way you shake it.

I didn't like B very much either. It also kind of sucks.

[LSAT-Chang]

What I mean is perhaps it take "longer". (How much longer who knows since the use of "longer" here is pretty ambiguous) but b/c the nectar provides more energy the increase in time is offset by the increase of energy provided by the given amount of nectar. I realize you would have to assume this, but that's why I had a hard time with this answer choice b/c it seems you would have to insert an assumption either way you shake it.

Hmm.. I'm not fully understanding your point, but I would love to try and help you understand why answer choice (C), if negated, would just destroy the conclusion.

So the author is concluding that the seed-eating bird spends more time eating than the nectar-eating bird (when both have same overall energy requirement) because the amount of nectar provides more energy than does the same amount of seeds. So basically, I understood this to mean that the nectar-eating birds reach the energy requirement faster than the seed-eating birds since there is more energy in the amount of nectar (so the seed-eating birds would have to sit there and eat longer to fulfill the energy requirement). When we negate (C) -- we get: "the time it takes for the nectar-eating bird to eat a given amount of nectar is LONGER than the time it takes the seed-eating bird to eat the same amount of seeds". Well if this is the case, then the nectar-eating birds would be spending more of their time eating than the seed-eating birds, which would destroy the conclusion that seed-eating birds spend more time eating than the nectar-eating birds.

As to your point about "longer" -- I didn't think it was too ambiguous since it just refers to the time it takes to eat the given amount of nectar or seeds.. sorry if I didn't address your point directly -- I just wanted to see if I could help in any way!

[chike_eze]

What I mean is perhaps it take "longer". (How much longer who knows since the use of "longer" here is pretty ambiguous) but b/c the nectar provides more energy the increase in time is offset by the increase of energy provided by the given amount of nectar. I realize you would have to assume this, but that's why I had a hard time with this answer choice b/c it seems you would have to insert an assumption either way you shake it.

I didn't like B very much either. It also kind of sucks.

I think Timmy's post addresses this question sufficiently. I also like the relevant analogy using "soup and steak" -- interesting. I'd like to put my spin on this question with a relevant example -- hope it makes sense

Overall Energy requirement: 20 joules
> therefore, Both birds require 20 joules of energy

Let's say 1 nectar is the same size as 1 seed bunch
> i.e., 1 nectar = 1 seed bunch

This is the "possible scenario" in (C) that undermines the Argument:
1 nectar = 20 joules
1 seed bunch = 10 joules

However,
Nectar-eating bird takes 2 hours to eat 1 nectar
Seed-eating bird takes 1 hour to eat 1 seed bunch

therefore,
In this scenario, both birds are able to receive the required 20 joules of energy in 2 hours. Based on this possibility, it is not necessarily the case that a seed-eating bird will spend more time eating than the nectar-eating bird.

Note: Nectar-eating bird could take 4 hours to eat 1 nectar. Now that would undermine the argument even more.

[bbirdwell]

JOULES! WOw

I like that you made an example with numbers. I think that helps hit the point home.

(B) is an interesting choice, and I can see why people choose it. This can be avoided in three ways, I think. The first is to focus on the conclusion, which is about TIME. This answer choice attempts to deal only with the premises, which is a big no-no on assumption questions and a red flag that the answer is incorrect.

A second way to look at it is that this is not really "assumed." In fact, it's stated: there are nectar-eating birds, and seed-eating birds.

Finally, we can negate. Negated, this choice doesn't affect the argument in any concrete way. So they sometimes eat seeds. So what? This might slow them down a little, if all other assumptions are made, but by virtue of the fact that this is only SOMETIMES, and the rest of the time they are eating nectar, which is faster, the nectar-eating/sometimes-seed birds would still be faster than the ONLY seed-eating birds. See?

It's so loose and requires a host of other assumptions to make it valid. Even if you can't confidently eliminate a choice like this, you should lean toward a choice like (C) that actually addresses the important part of the CONCLUSION (time), and clearly affects the argument when negated.

Great discussion, guys.

[esultana]

This discussion has been very helpful (my original answer was B). However, I would like to discuss why I originally disregarded answer C.

The argument concludes that the seed-eating bird spends more time eating than the nectar-eating bird. Or, the nectar-eating bird spends less time eating than the seed-eating bird.

time(seed) > time(nectar)

Answer C states that the nectar-eating bird's eating time is not longer than the seed-eating bird, which is all well and good. This agrees with the argument that time(seed) > time(nectar).

However (to me) this does not discount that the nectar-eating bird could take the same exact amount of time to eat the nectar as the seed-eating bird takes to eat the seeds.

time(seed) = time(nectar)

Because "not longer" does not discount the same exact amount of time. If this is taken into account, C does not fully support the argument.

[bbirdwell]

However (to me) this does not discount that the nectar-eating bird could take the same exact amount of time to eat the nectar as the seed-eating bird takes to eat the seeds.

The answer does not need to take this into account.

Don't forget what we're actually looking for here. Our job is not to select an answer that "fully supports" or "guarantees" the argument. Our job is to find a necessary assumption, which is simply something that is required to make the argument valid. Thus, (C) is inarguably correct.

What you are pointing out is that (C) is not sufficient to guarantee the conclusion. And you're right. And that's totally fine because we're not looking for a sufficient assumption. Just a necessary one.

[esultana]

Aha! Thank you.

[rgrijalb]

Still having a bit of trouble with C. I feel like the negation of it would have to assume that the longer time it takes to eat the given amount of nectar is not offset by the concomitant advantage of the increased amount of energy contained in the given amount of nectar.

What I mean is perhaps it take "longer". (How much longer who knows since the use of "longer" here is pretty ambiguous) but b/c the nectar provides more energy the increase in time is offset by the increase of energy provided by the given amount of nectar. I realize you would have to assume this, but that's why I had a hard time with this answer choice b/c it seems you would have to insert an assumption either way you shake it.

I didn't like B very much either. It also kind of sucks.

I completely understand your reasoning. Let me try to clarify this. First of all consider that both birds require 10 J energy, seed birds can obtain 1J per given unit of seed, whereas nectar birds can obtain 5J per similar given unit of nectar. What Gaverett is saying is consider the negation of (C) and its' implications on the low end of the spectrum of values: to eat a given unit of seed would take 2 min, hence seed birds would take 20 min to satisfy their energy requirement, whereas nectar birds take 3 minutes to eat a given unit of nectar, hence NECTAR BIRDS WOULD TAKE LONGER (+1min longer/unit) TO EAT A SIMILAR GIVEN AMOUNT OF FOOD AS DO SEED BIRDS but the conclusion that nectar birds would STILL spend less time eating (to obtain the energy requirement of 10 J) is VALID since they would only require 2 units of nectar and spend 6 minutes eating whereas seed birds would require 10 units of seed and spend 20minutes eating.

Better answer to this question would be : "amount of time it takes to eat a given amount of food necessary to satisfy a nectar bird energy requirement is not longer than the amount of time it takes to eat a given amount of food necessary to satisfy a seed bird energy requirement".

So though (C) would seem unnecessary when you consider the difference in energy provided per unit to be high and the difference in time to eat a given amount of food to be low, when the reverse is true, such as most posters on this have already shown (time eating difference is high; energy difference provided per unit is low), the negation of such a statement surely weakens the conclusion, afterall we are not setting out to prove the conclusion is outright wrong, just the answer that would, when negated, most weaken the conclusion. Had there been an answer when the extreme values on both sides of the spectrum both weakened the conclusion (compared to (C) which only had one of both extreme values weaken the conclusion) it would surely be superior to (C) and hence correct, but this is not the case.

[stm_512]

Still having a bit of trouble with C. I feel like the negation of it would have to assume that the longer time it takes to eat the given amount of nectar is not offset by the concomitant advantage of the increased amount of energy contained in the given amount of nectar.

What I mean is perhaps it take "longer". (How much longer who knows since the use of "longer" here is pretty ambiguous) but b/c the nectar provides more energy the increase in time is offset by the increase of energy provided by the given amount of nectar. I realize you would have to assume this, but that's why I had a hard time with this answer choice b/c it seems you would have to insert an assumption either way you shake it.

I didn't like B very much either. It also kind of sucks.

I completely understand your reasoning. Let me try to clarify this. First of all consider that both birds require 10 J energy, seed birds can obtain 1J per given unit of seed, whereas nectar birds can obtain 5J per similar given unit of nectar. What Gaverett is saying is consider the negation of (C) and its' implications on the low end of the spectrum of values: to eat a given unit of seed would take 2 min, hence seed birds would take 20 min to satisfy their energy requirement, whereas nectar birds take 3 minutes to eat a given unit of nectar, hence NECTAR BIRDS WOULD TAKE LONGER (+1min longer/unit) TO EAT A SIMILAR GIVEN AMOUNT OF FOOD AS DO SEED BIRDS but the conclusion that nectar birds would STILL spend less time eating (to obtain the energy requirement of 10 J) is VALID since they would only require 2 units of nectar and spend 6 minutes eating whereas seed birds would require 10 units of seed and spend 20minutes eating.

Better answer to this question would be : "amount of time it takes to eat a given amount of food necessary to satisfy a nectar bird energy requirement is not longer than the amount of time it takes to eat a given amount of food necessary to satisfy a seed bird energy requirement".

So though (C) would seem unnecessary when you consider the difference in energy provided per unit to be high and the difference in time to eat a given amount of food to be low, when the reverse is true, such as most posters on this have already shown (time eating difference is high; energy difference provided per unit is low), the negation of such a statement surely weakens the conclusion, afterall we are not setting out to prove the conclusion is outright wrong, just the answer that would, when negated, most weaken the conclusion. Had there been an answer when the extreme values on both sides of the spectrum both weakened the conclusion (compared to (C) which only had one of both extreme values weaken the conclusion) it would surely be superior to (C) and hence correct, but this is not the case.

I was going through similar thought process as well. The bolded scenario seems to clearly that C) is not a necessary assumption.

If the seed eating birds require more seeds to eat than nectar birds eating nectar, even if the nectar eating bird spends more time eating a given amount of nectar, the seed eating bird could still spending more time eating in order to satisfy its energy requirements!

I've now spent half an hour on this question, and I'm still not convinced that C is the right answer. Clearly, I have a blindspot!

Where is my blindspot?

[WaltGrace1983]

I was going through similar thought process as well. The bolded scenario seems to clearly that C) is not a necessary assumption.

If the seed eating birds require more seeds to eat than nectar birds eating nectar, even if the nectar eating bird spends more time eating a given amount of nectar, the seed eating bird could still spending more time eating in order to satisfy its energy requirements!

I've now spent half an hour on this question, and I'm still not convinced that C is the right answer. Clearly, I have a blindspot!

Where is my blindspot?

Your blind spot is an interpretation of the negation test that is slightly (but significantly) skewed, I think.

Let's go back to basics.

Seed-eating bird/nectar-eating bird = same energy requirement
+
Energy provided by (1) nectar > Energy provided by (1) seed**
→
Seed-eating bird spends more time eating than does the nectar-eating bird

** (1) nectar = (1) seed is simply meaning that it is the "same amount"

So we have a conclusion based off of this evidence. The evidence is that there is more energy provided by nectar than by the same amount of seeds. So what is the gap? The gap, as you already know, is that the argument is assuming that it is not significantly harder to eat the nectar and thus would take much more time to eat the nectar. Let me put this into perspective for you.

A relevant example:
You and I are both 6'0, 190 lbs, and male. We have the same muscle mass, fat, etc. Everything about us is the same. We must eat 2,000 calories in order to maintain our body. How do we do this?

Well I am a steak-eater but you aren't a big fan of steak and so you go with a big plate of bananas. We both got to get to 2,000 calories though! I tell you that I am going to finish first though because 1oz of steak has 55 calories while 1oz of bananas has 25 calories.

According to Google, eating 2,000 calories via steak would mean eating a 36 oz steak. HOLY COW! (literally?) However, it would take 20 bananas to get 2,000 calories.

By me telling you that I am going to finish first, I am assuming that it takes roughly the same amount of time to eat 1oz of steak versus 1oz of banana. This is clearly not true! I don't care how fast you can eat a steak - eating 20 bananas is WAY easier than eating a 36oz steak and it would take much less time.

Do you see what I mean?

Now back to the question.

We are drawing a conclusion on time from premises talking about an amount. How do we make this jump? Like the example above, we must assume that amount is roughly equal to time it takes to eat it.

(A) We already know that these birds have the same overall energy requirements. Nothing to assume here.

(B) It's fine if it sometimes eats seeds. We are specifically talking about comparing nectar to seeds. For the purposes of this question, it seems the nectar-eating bird is only eating nectar while the seed-eating bird is only eating seeds and we are simply comparing the time it takes them to do so.

(E) We don't care what the energy requirements consists of or why it is the way it is. We have no reason to question this!

(D) This is certainly tempting. However, it doesn't really have much to do with the premise-conclusion link! Now I know that we cannot merely say that (D) is simply relying on "irrelevant background information." After all, the body temperature surely is relevant to this whole process. However, do we absolutely know that you have to eat more in order to maintain the body temperature? We don't really know that much about body temperature. If we had more information in the actual premises we might be able to say this is necessary.

In addition, negating (D) wouldn't actually destroy the argument. Let's say the seed-eating bird has a 1 degree F less body temperature. The huge gap between the premises/conclusion still exists in a very profound way AND we don't know how eating affects the body temperature. Would I keep this answer on the initial pass? Probably. Is it better than (C)? No way.

(C) "The time it takes for a nectar-eating bird to eat a given amount of nectar IS longer than the time it takes the seed-eating bird to eat the same amount of seeds." All of a sudden, our premises do not lead to the conclusion. From the basis of a given amount of nectar providing more energy than the same amount of seeds, we have no idea if the conclusion follows (when we put this negated C in). THAT is what I think is going on with a lot of these questions.

Negating (C) doesn't invalidate the conclusion. It invalidates the conclusion FROM THE PREMISES. It makes it so the premises don't really lead to a reasonable person concluding the conclusion.

You got me?

[cyt5015]

We got good discussion above, but I'd like to clarify a confusion about "the eating time" here.
The eating time in the argument actually has two meanings (1) the amount of time to eat the food for reaching the same given overall energy requirement and (2) the amount of time to finish the same given amount of food (an indicator for how difficult to eat the food). Answer C refers to the second meaning and the conclusion refers to the first meaning.

Answer C blocks the possibility that nectar is more difficult to eat than seeds.

I dwelled a little on answer B, and eliminate it eventually, here is my reasoning:
answer B is another way to say that nectar-eating bird always eats nectar and never eats seeds. I'm sure if it were expressed in that way, more people will eliminate confidently. Is that assumption necessary? Let's negate it as nectar-eating bird sometime eat seeds. "some" in our concept could range from 1 to 100, but here it has to mean less than 50%, otherwise, this kind of bird should be named as "seed-eating bird" or "seed-eating and nectar eating bird (eat 50-50)".
Suppose the nectar-eating bird has a diet composing of 51% nectar and 49% seeds. The author's conclusion still holds even if the nectar-eating bird only surpass the seed-eating bird a tiny bit on speed to finish the food which meets the same overall energy requirement.

The fact that "body temperature" in answer D appears in context (background information) not in the argument should raise a red flag if choosing this answer.

[daijob]

I'm still not sure why C is the answer...
I originally chose B, because the stimuli does not say nectar eating bird only eats nectar and thought this is necessary to assume to conclude "the seed-eating bird spends more time eating than does the nectar-eating bird."
(Actually, does nectar-eating bird mean they only eat nectar?)
I eliminated C because I thought C only repeats what the stimuli says-especially the conclusion...
How are conclusion and C different??
Both talk about time, isn't it?
Or is it because of the word "the same amount" ?

Thank you

[maryadkins]

Both talk about time, but it's in a different sense.

The conclusion is saying the seed-eating birds spend more time, in total, eating.

(C) says that the comparative amount of time it takes to eat nectar isn't greater than how much time it takes to eat seeds. If it takes longer to eat nectar than to eat seeds, the conclusion doesn't follow from the premises anymore—birds that eat seeds aren't going to spend more time necessarily eating than birds that eat nectar.

And to answer your question, because the question distinguishes between the two types of birds in the premises, we take that distinction as true: there are birds that eat seeds, and there are birds that eat nectar. If there are birds that eat both, they aren't relevant here.