I do not understand the assumption in the rationale of the correct answer to this (most strongly supported) question.
[edited: content removed]
Excerpt from rationale: "Firstly, the last sentence of the stimulus shows that the amount of rhodopsin molecular motion is directly proportional to the temperature of the retina (meaning that when temperatures are lower, molecular motion is lower; when temps are higher, molecular motion is higher).
My confusion: How does one induce the proportional relationship between temperature and molecular motion to be more active in warmer climates than in colder ones? Is it not possible based upon the information given in the stimulus that this relationship could be reverse, meaning more active in cold climates and less active in hot?
Please help. I believe this to be a failure on part of the Makers of the test to define how the temperature "relationship" works. Leaves it up to the test takers to make the assumption that the correlation is as above mentioned in the rationale, but it could plausibly exist in the opposite direction.
Ch 4. Pg 121 Q:7
Thanks for your question. Note that I've removed portions of your post in which you copied and pasted portions of the original question, to comply with LSAC's copyright regulations.
Onto your question: the last sentence of the stimulus states that the amount of molecular motion of the molecule rhodopsin is directly proportional to the temperature of the retina. In other words, the warmer the retina, the more molecular motion there is, and - inversely - the colder the retina, the less molecular motion. This is the essence of direct proportionality: we have a positive correlation between motion and temperature. If the relationship was reversed, the last sentence would have said, "The amount of molecular motion is inversely proportional to the temperature of the retina."
So, if the visual system of the animal matches that of its surroundings, then the molecular motion will be higher when the surrounding temperature (and, hence, the animal's own body temperature) is higher. Given the information presented in the second sentence of the stimulus, the visual system of such an animal would be more error-prone.
This is a perfectly valid question from a logical standpoint. In fact, all questions on the LSAT are logically valid; the few that weren't, at the time they were administered, were subsequently removed from scoring. The LSAT is an exceptionally well-made test, so resist the urge to argue with it You'll never win.
Hope this helps! Let me know.
PowerScore Test Preparation
I came to this realization soon after I posted the question. I guess my confusion stemmed from the meaning of "directly proportional". Thanks for the quick response!
I am writing because I also had an issue with the vocabulary of this question, due to the usage of terminology, and not based on the logical structure of the stimulus.
After reading Nikki's explanation, and then conducting research, I have to continue to argue that the usage of "directly proportional" is terminology largely used in the scientific and mathematical communities, and not used much elsewhere. Therefore, it cannot be expected to be commonly known that "directly proportional" can only be a positive correlation between temperature and molecular motion. Logically, someone who is not familiar with the usage of this terminology in the scientific and mathematical communities could assume that temperature and motion are definitely proportional, but not that one definitely only increases when the other increases. As anthonycarral states, a person not knowledgeable in the mathematical and scientific usage of this terminology could logically deduce that motion decreases when temperature increases, or it could be vice versa - therefore choosing one direction over the other would be perceived by the test taker as guessing an answer, or adding outside information to the stimulus.
Logically, if this additional clarifying information had been presented in the stimulus, I would have had no problem selecting the correct answer provided. However, without having this information clarified in the stimulus, choosing the correct answer out of the choices provided became a guessing game, as none of the choices could be proven/supported fully by the stimulus without incorporating outside information.
Thanks for the question!
I hear you; it doesn't seem like you should be expected to know the meaning of that term, which feels like more of a term of art to you. Unfortunately, the makers of the LSAT don't agree; there are several other questions that have used the term "directly proportional" in tests over the years. This is one of those things that, unfortunately, you might not know on test day unless you had a reason to be familiar with the term--and in fact, other LSAT questions also require some understanding of math/math terms, as you are asked to identify reasoning flaws related to numbers and percentages, etc. The good news is, now you know this term! You'll be ready next time it comes up, and you'll be prepared to see this on test day. This is one of the reasons a good prep course or plan is so important, because you're exposed in the course of studying to things just such as this; you may get tripped up on the practice question, but then you'll know it after that. Great job really thinking through this and digging in; the more you invest understanding questions you got wrong, the more prepared you'll be in the future, and the more you'll get out of your studying!
Thanks for your reply. I guess at some point we have to just learn things the way they are and can't always have things changed to the way we think they should be! And yes, I am starting to come to the realization that even though I have considered myself having a strong foundation in formal logic, without a proper prep course such as the ones offered by PowerScore, I would have been completely clueless on LSAT test day.
Hi--simple question on this. Why is it OK to assume we are talking about animals' retinas as opposed to humans'? When I answered this question, I immediately ruled out those answers that included this information. I realize humans are animals, but it seems like an introduction of new info to me given the stimulus did not specify animals and seems like a stretch for the umbrella concept (lion=animal).
Interesting question, aec2j - mind if I turn it around on you for a moment? What makes you think we are talking about humans' retinas here?
Two things to note here that might help you some. The first is that, yes, humans are animals - this is an idea that is tested frequently on the LSAT (much like the concepts of direct vs inverse proportions, discussed here previously). You are expected to know that any claim made about animals generally applies to humans unless otherwise noted.
Second thing is that this stimulus is entirely general. It is about vision, retinas, photons, rhodopsin, all in the most general of terms. We can't assume that it refers only to certain animals, or to humans, or even that it is limited to earthlings. We might be able to draw conclusions about Martians based on this, if we were to learn that they, too, have retinas and rhodopsin.
So, the introduction of "animals" here is not new information, as long as you accept from the start that we are talking about an anatomical system found in animals (as opposed to, say, rocks and trees, which only have retinas in scary movies and children's tv shows, I think).
The more important lesson to take away here is probably the first one - it's never about "animals as opposed to humans" because humans are animals. That is a standard concept found throughout the test (and in the real world - just ask any vegan, or any scientist for that matter), and while we might sometimes feel bruised egos when we think that we are being put in the same category as mice and lemurs and hippos, we have to put those egos aside and accept that we are all in this thing together. Except for the LSAT, that is - lemurs almost never take this test. Lucky lemurs.
Good luck, fellow animal!
Adam M. Tyson
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I, like many before me, fell prey to being confused by "direct proportionality." Looking at the dates from this thread, I'm wondering why this question remains in the LRB Must be true practice set. I've run into a handful of questions difficult for me in the practice sets of the PowerScore curriculum where I search for questions in these forums and the response from PowerScore will usually be something to the effect of "the reason you got this question wrong is because it involved some notorious LSAT vocabulary that you haven't encountered yet. But hold on, you'll get there!" Wouldn't it be easier to include that vocab earlier on in the curriculum, or refrain from using questions with advanced vocabulary in earlier chapters? Or maybe even include an index at the end of the books so I can find the term "direct proportionality?"
My 2016 edition of the Logical Reasoning bible provides what amounts to a definition in the explanation of this question on page 138. If you have the 2017 edition, I believe it will appear on or around page 127:
It is often hard to say what vocabulary is "advanced." When dealing with an economics stimulus, some of my students need a explanation of what inflation is, while others will consider the concept to be elementary. In any case, if you look at the explanations in the book, we try to be as broad as possible in considering what background knowledge test-takers will have.
We do include distinct vocabulary lists and/or explanations for conditional relationships, causal relationships, numbers and percentages, premise and conclusion indicators, formal logic, and common errors of reasoning in this book. Those are just the ones I can remember off the top of my head.
There is a lot of vocabulary that the LSAT considers to be fair game. To include every single "advanced" vocabulary terms at the beginning of the book would make for an incredibly long and tedious read. To put off presenting questions with any "advanced" vocabulary would limit the questions we could include to a rather small set of questions.
I know it can be irritating when you read "hold on, you'll get there!" when you just spent a half hour or more struggling on a single question. I would just add that every time you struggle with a concept to this extent, understand that you are thoroughly imprinting that new concept into your memory, and you will not overlook it again.