There is no consensus among researchers regarding what qualifies a substance as a pheromone. While most agree on a basic...
GMAT Reading Comprehension : (RC) Questions
There is no consensus among researchers regarding what qualifies a substance as a pheromone. While most agree on a basic definition of pheromones as chemicals released by one individual of a species which, when detected by another individual of the same species, elicit a specific behavioral or physiological response, some researchers also specify that the response to pheromones must be unconscious. In addition, the distinction between pheromones and odorants—chemicals that are consciously detected as odors—can be blurry, and some researchers classify pheromones as a type of odorant. Evidence that pheromone responses may not involve conscious odor perception comes from the finding that in many species, pheromones are processed by the vomeronasal (or accessory olfactory) system, which uses a special structure in the nose, the vomeronasal organ (VNO), to receive chemical signals. The neural connections between the VNO and the brain are separate from those of the main olfactory system, whose processing of odorants triggers sensations of smell. But while the VNO does process many animal pheromone signals, not all animal pheromones work through the VNO. Conversely, not all chemical signals transmitted via the VNO qualify as pheromones. For example, garter snakes detect a chemical signal from earthworms—one of their favorite foods—via the VNO, and they use this signal to track their prey.
It can be inferred from the passage that in classifying pheromones as a type of odorant, the researchers referred to the highlighted text posit that
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| There is no consensus among researchers regarding what qualifies a substance as a pheromone. | What it says: Scientists disagree about how to define pheromones. What it does: Introduces the main problem/debate the passage will explore Source/Type: Author's factual observation about the research community Connection to Previous Sentences: Opening statement - no prior context Visualization: Imagine 100 researchers: 30 say pheromones must be unconscious, 25 say they can be conscious, 20 say they're just special odors, 25 have other definitions Reading Strategy Insight: This signals the passage will clarify a confusing topic - expect definitions and examples to help sort out the confusion What We Know So Far: Pheromone definition is disputed What We Don't Know Yet: What the competing definitions are, why there's disagreement |
| While most agree on a basic definition of pheromones as chemicals released by one individual of a species which, when detected by another individual of the same species, elicit a specific behavioral or physiological response, some researchers also specify that the response to pheromones must be unconscious. | What it says: Most scientists agree pheromones are chemicals that cause reactions between same-species animals, but some add that the reactions must be unconscious. What it does: Provides the basic agreed-upon definition plus the main point of disagreement Source/Type: Factual summary of researcher positions Connection to Previous Sentences: This directly explains what sentence 1 meant by "no consensus" - shows there IS agreement on basics but disagreement on consciousness requirement Visualization: Basic definition (agreed by 85/100 researchers): Animal A releases chemical → Animal B detects it → Animal B reacts. Disagreement: 40 researchers say B must be unaware, 45 say B can be aware Reading Strategy Insight: Feel relieved here - this clarifies the confusion from sentence 1 rather than adding new complexity What We Know So Far: Basic pheromone definition, consciousness requirement debate What We Don't Know Yet: How this relates to odors, what evidence supports different views |
| In addition, the distinction between pheromones and odorants—chemicals that are consciously detected as odors—can be blurry, and some researchers classify pheromones as a type of odorant. | What it says: The line between pheromones and smell chemicals is unclear; some scientists think pheromones are just a type of smell. What it does: Introduces a second area of definitional disagreement Source/Type: Author's summary of another research debate Connection to Previous Sentences: This builds on sentence 2's consciousness debate - if pheromones can be conscious (as some researchers argue), then they might overlap with regular odors Visualization: Two overlapping circles: Pheromones (trigger specific behaviors) and Odorants (consciously smelled). Some researchers see 50% overlap, others see 0% overlap Reading Strategy Insight: This connects logically to the consciousness debate - we're seeing how one disagreement leads to another What We Know So Far: Basic definition, consciousness debate, pheromone vs. odor debate What We Don't Know Yet: What evidence exists for these different positions |
| Evidence that pheromone responses may not involve conscious odor perception comes from the finding that in many species, pheromones are processed by the vomeronasal (or accessory olfactory) system, which uses a special structure in the nose, the vomeronasal organ (VNO), to receive chemical signals. | What it says: Support for unconscious pheromones: many animals have a special nose structure (VNO) that processes pheromones separately from regular smell. What it does: Provides evidence for one side of the consciousness debate Source/Type: Scientific evidence/research finding Connection to Previous Sentences: This directly addresses the consciousness question from sentence 2 - gives concrete evidence for the "unconscious" camp Visualization: Animal nose with two systems: Regular nose (processes 1000 odors consciously) + VNO (processes 20 pheromones unconsciously) Reading Strategy Insight: This simplifies the debate by giving concrete evidence - we're moving from abstract disagreement to specific proof What We Know So Far: Definitional debates + evidence that some pheromones use separate unconscious system What We Don't Know Yet: How complete this evidence is |
| The neural connections between the VNO and the brain are separate from those of the main olfactory system, whose processing of odorants triggers sensations of smell. | What it says: The VNO connects to different brain parts than regular smell does - regular smell goes to consciousness centers, VNO doesn't. What it does: Reinforces and explains the previous sentence's evidence Source/Type: Additional scientific detail supporting the evidence Connection to Previous Sentences: This restates sentence 4's evidence in more detail - explains WHY the VNO supports unconscious processing Visualization: Brain diagram: Regular smell pathway goes Nose → Smell center → Consciousness. VNO pathway goes VNO → Different brain area → Behavior (bypassing consciousness) Reading Strategy Insight: This is elaboration, not new complexity - the author is helping us understand the VNO evidence better What We Know So Far: Same as before, but with clearer understanding of VNO mechanism What We Don't Know Yet: Whether VNO evidence completely settles the debate |
| But while the VNO does process many animal pheromone signals, not all animal pheromones work through the VNO. | What it says: The VNO handles many but not all pheromones. What it does: Limits/qualifies the VNO evidence presented in sentences 4-5 Source/Type: Scientific fact that complicates the evidence Connection to Previous Sentences: This contrasts with the strong VNO evidence - shows the unconscious camp's evidence isn't complete Visualization: Pheromone processing: 70 pheromones use VNO (unconscious), 30 pheromones use regular nose system (possibly conscious) Reading Strategy Insight: The author is being balanced - showing that even promising evidence has limitations What We Know So Far: VNO provides partial but incomplete support for unconscious theory What We Don't Know Yet: What this means for the overall debate |
| Conversely, not all chemical signals transmitted via the VNO qualify as pheromones. | What it says: Some chemicals go through the VNO but aren't pheromones. What it does: Further limits the VNO evidence by showing VNO isn't exclusive to pheromones Source/Type: Scientific fact that further qualifies the evidence Connection to Previous Sentences: This builds on sentence 6's limitation - shows VNO evidence is problematic in both directions Visualization: VNO processes 100 chemical signals: 70 are pheromones + 30 are other chemicals (like prey-tracking signals) Reading Strategy Insight: We're seeing a pattern: promising evidence gets qualified and limited - this is typical in scientific discussions What We Know So Far: VNO and pheromone relationship is partial and imperfect What We Don't Know Yet: What example will illustrate this point |
| For example, garter snakes detect a chemical signal from earthworms—one of their favorite foods—via the VNO, and they use this signal to track their prey. | What it says: Garter snakes use their VNO to smell earthworms for hunting, not for communicating with other snakes. What it does: Provides concrete example of sentence 7's point about non-pheromonal VNO use Source/Type: Specific scientific example Connection to Previous Sentences: This illustrates sentence 7's abstract point with a concrete case - VNO chemical that isn't a pheromone because it's between different species Visualization: Garter snake's VNO detecting: 15 snake pheromones (same species communication) + 8 prey chemicals like earthworm scent (different species, hunting) Reading Strategy Insight: Feel confident here - this example clarifies rather than complicates. It shows why VNO ≠ pheromone What We Know So Far: Pheromone definition remains unsettled; VNO evidence is suggestive but incomplete What We Don't Know Yet: Passage appears complete - the definitional consensus remains elusive |
2. Passage Summary:
Author's Purpose:
To explain why scientists disagree about how to define pheromones by showing the complexity of the evidence used to classify these chemicals.
Summary of Passage Structure:
In this passage, the author walks us through a scientific debate and examines the evidence on both sides:
- First, the author introduces the problem by stating that researchers disagree about what counts as a pheromone
- Next, the author explains the basic definition most scientists accept and identifies the main disagreement about whether pheromone responses must be unconscious
- Then, the author presents evidence that seems to support the unconscious view by describing a special organ that processes chemicals separately from regular smell
- Finally, the author shows that this evidence is incomplete by pointing out that the special organ doesn't handle all pheromones and also processes non-pheromone chemicals
Main Point:
The debate over how to define pheromones continues because even the most promising scientific evidence has significant limitations and doesn't clearly resolve the disagreements between researchers.
3. Question Analysis:
This question asks us to infer what researchers who classify pheromones as a type of odorant must believe about pheromones. The key phrase is "in classifying pheromones as a type of odorant" - we need to understand what logical assumption these researchers are making.
Connecting to Our Passage Analysis:
From our passage analysis, we identified several key points:
- There's a debate about whether pheromone responses must be unconscious
- The passage defines odorants as "chemicals that are consciously detected as odors"
- Some researchers classify pheromones as a type of odorant, which creates a "blurry" distinction
- The VNO evidence supports unconscious processing, but this evidence is incomplete
The critical insight from sentence 3 of our analysis shows that if researchers classify pheromones as odorants, and odorants are by definition "consciously detected," then these researchers must believe pheromones can be consciously perceived.
Prethinking:
If researchers classify pheromones as a type of odorant, they're essentially saying pheromones belong to the category of "chemicals that are consciously detected as odors." This directly contradicts the view that pheromone responses must be unconscious. Therefore, these researchers must believe that pheromones are perceived consciously - otherwise, they wouldn't classify them as odorants.
Why It's Right:
- The passage defines odorants as "chemicals that are consciously detected as odors"
- If researchers classify pheromones as a type of odorant, they must believe pheromones share the key characteristic of odorants - conscious detection
- This directly connects to the consciousness debate outlined in the passage
Key Evidence: "the distinction between pheromones and odorants—chemicals that are consciously detected as odors—can be blurry, and some researchers classify pheromones as a type of odorant."
Why It's Wrong:
- This focuses on the processing mechanism rather than the classification logic
- The passage shows VNO processing is incomplete evidence - not all pheromones use the VNO
- Researchers who classify pheromones as odorants wouldn't necessarily focus on VNO statistics
Common Student Mistakes:
- Thinking the VNO evidence is the main point of the passage? → Focus on how the classification debate relates to consciousness, not processing mechanisms
- Confusing what most pheromones do with what researchers who make specific classifications believe? → Distinguish between general facts and specific researcher positions
Why It's Wrong:
- This reverses the relationship described in the passage
- The passage states "not all chemical signals transmitted via the VNO qualify as pheromones"
- This choice confuses the direction of the classification relationship
Common Student Mistakes:
- Mixing up the VNO limitations mentioned in the passage? → Remember the passage says VNO processes non-pheromone signals like prey detection
- Focusing on VNO statistics instead of odorant classification logic? → The question asks about researchers who classify pheromones as odorants, not VNO researchers
Why It's Wrong:
- This contradicts the basic definition that most researchers accept
- The passage clearly states the basic definition requires same-species interaction
- The garter snake example actually reinforces species specificity by showing non-pheromonal chemical detection
Common Student Mistakes:
- Misinterpreting the garter snake example as expanding pheromone definition? → The example shows what's NOT a pheromone because it's between different species
- Thinking the classification as odorants changes species requirements? → Odorant classification relates to consciousness, not species specificity
Why It's Wrong:
- This contradicts the basic agreed-upon definition of pheromones
- The passage states most researchers agree pheromones "elicit a specific behavioral or physiological response"
- Classifying pheromones as odorants doesn't change their response-triggering nature
Common Student Mistakes:
- Thinking odorant classification weakens the response requirement? → Odorants can still trigger specific responses while being consciously perceived
- Confusing the consciousness debate with the response requirement? → These are separate aspects of pheromone definition