Answers and Explanations—3.9 Synesthesia

P1	Paragraph 1	Comments
S1	Does the sound of music have a color to you?
2	Can you taste the sight of a particular shade of blue?
3	Few people can.
4	For most of us, the five primary senses—sight, hearing, taste, smell, and touch—are distinct categories; our brains process these sensory experiences as separate from one another and fundamentally unique.	For most people, the five senses are distinct.
5	But for certain people known as “synesthetes,” things are not so straightforward.	Synesthetes.
6	For these people, the stimulation of one sense may trigger the activation of one or more other senses.	Synesthetes = one sense can trigger others.

	The word “shade” in the passage is closest in meaning to	VOCABULARY. In the context of colors, “shade” = particular tint, hue, or tonal variation in color.
✓	A hue	Correct. “A particular shade of blue” = a particular hue or variation of the color blue.
✗	B glimpse	Not quite. “Glimpse” = a quick sight of something. It’s not a synonym for “shade.”
✗	C shadow	In other contexts, “shade” = shadow or darkness. “A particular shadow of blue” is not idiomatic English.
✗	D light	“A particular light of blue” is not idiomatic English either. As a countable noun (one light, two lights), “a light” most often means a light fixture, a lamp or lantern. That doesn’t make sense here.

	Which of the following can be inferred from paragraph 1?	Inference. You must be able to prove the correct answer, using only the words in this paragraph.
✗	A The purpose of sensory perception is to separate sensory experiences into separate categories.	P1 does not discuss the purposes of sensory perception.
✗	B Generally, synesthetes process sensory experiences as unique and independent.	Opposite. S5 introduces synesthetes by way of contrast to “most of us,” who process sensory experiences as separate and unique (S4).
✗	C Sensory perception is substantially more difficult for synesthetes than for others.	S5–6 discuss how “things are not so straightforward” for synesthetes, for whom an experience of one sense can trigger the experience of another. This may seem to make sensory perception substantially more difficult for synesthetes. But from the text you’re given in P1, you can’t properly draw that conclusion. All you know from P1 is that by being mixed in some way, sensory experiences are different for synesthetes.
✓	D Synesthetes do not always perceive different sensory experiences as separate and unique.	Correct. S6: “For these people [synesthetes], the stimulation of one sense may trigger the activation of one or more other senses.” Synesthetes are contrasted to “most of us” (S4), who perceive sensory experiences as separate.

P2	Paragraph 2	Comments
S1	Just how prevalent synesthesia is remains unknown.	No one knows how prevalent synesthesia is.
2	Estimates range from 1 in 20 people to 1 in 25,000 people.
3	The most common type of synesthesia is called “grapheme-color synesthesia,” or seeing different letters as different colors.	Most common type: see letters with colors.
4	Still, there are many people who experience other forms of overlapping senses.	But there are other types.
5	One such person was the American composer Leonard Bernstein, who reported that when he listened to music, the timbre of various sounds appeared to him visually as varied colors.

	The word “prevalent” in the passage is closest in meaning to	VOCABULARY. “Prevalent” = common, frequent, widespread.
✗	A successful	Not quite. The use of “successful” in this context would not be clear. Would it mean “successful at establishing itself in humans” (like a disease or other condition), or “successful in allowing synesthetes to interpret sensory information," or something else entirely?
✓	B common	Correct. “Just how prevalent synesthesia is remains unknown” = it is still not known how common or widespread synesthesia is.
✗	C influential	These words might be related but aren’t necessarily. Something that is influential (having great influence on someone or something) might also be prevalent, but it might be extremely rare as well.
✗	D unfavorable	These words are unrelated. Something unfavorable has a lack of support or approval. It has no bearing on how common or uncommon it is.

	According to paragraph 2, what kind of synesthesia did Leonard Bernstein experience?	Fact. S5 mentions Leonard Bernstein as an example of a synesthete.
✗	A When the colors in his field of vision changed, he heard different sounds.	S5 describes the opposite experience: different sounds in the world produced different colors in Bernstein’s mind, not the other way around.
✓	B Different qualities of sounds appeared to him as various colors.	Correct. S5: “when he listened to music, the timbre of various sounds appeared to him visually as varied colors.” That is, as the sounds Bernstein heard changed in quality, he saw different things.
✗	C The louder the music he heard was, the more colorful his vision became.	The volume, or loudness, of the music is not discussed in S5.
✗	D It was impossible for him to hear music without seeing letters.	S5 states that Bernstein saw colors, not letters, when he listened to music.

	Paragraphs 3-4	Comments
P3 S1	Other synesthetes may even have multiple forms of the condition at once.	Can even have multiple forms of synesthesia.
2	Twentieth-century Russian journalist Solomon Shereshevsky, for example, is reputed to have had a spectacular memory—he could memorize a speech word for word after hearing it only once, and could remember a complicated math formula within a strikingly short time frame.	Example.
3	The method by which he did so was synesthesia, which for him existed among all five senses.	Amazing memory because his synesthesia involved all 5 senses.
P4 S1	How does synesthesia work?	How it works.
2	In recent decades, scientists have been able to uncover the neurological basis for some kinds of synesthesia.	Neurological basis.
3	Grapheme-color synesthetes, for example, display uncharacteristic neural activity in the color-based region of the visual cortex of their brains while reading, while people who are not grapheme-color synesthetes do not.	Example.

	According to paragraph 3, Solomon Shereshevsky had a remarkable memory because of which of the following?	Fact. S2–3 describe Shereshevsky’s memory and the reason for it.
✗	A He could quickly recall complex math formulas.	This is an example of Shereshevsky’s remarkable memory, not the reason for it.
✗	B He primarily used vivid colors to remember.	Not supported.
✓	C His memories involved several senses at once.	Correct. S3: “The method by which he did so was synesthesia, which for him existed among all five senses.” That is, his sensory experiences and his memories of those experiences involved several of his senses at the same time. Synesthesia is defined earlier, but it is the topic of the passage. What it means should be familiar by now.
✗	D He worked as a Russian journalist in the twentieth century.	Shereshevsky is identified as a “twentieth-century Russian journalist” (S2). But this is not given as the reason for his spectacular memory.

	Which of the sentences below best expresses the essential information in the highlighted portion of the passage? Incorrect choices change the meaning in important ways or leave out essential information.	Simplify Sentence. S3 gives an example of the “neurological basis” that scientists have found for some kinds of synesthesia.
✓	A When grapheme-color synesthetes read, a region of their brains related to perceiving color are unusually active.	Correct. Using fewer words, this version captures the meaning of the original. “Unusually” is enough to convey both “uncharacteristic” and the whole clause beginning with “while,” which is unnecessary.
✗	B Grapheme-color synesthetes read when their brains display unusual activity in a color-based region of the visual cortex.	This reverses the causality in the original sentence. The unusual brain activity doesn’t cause these synesthetes to read. Rather, the reading causes the unusual brain activity.
✗	C While reading text in various colors, grapheme-color synesthetes show unusual activity in the visual cortex of their brains.	The original does not mention reading text “in various colors.” This is important, because these synesthetes experience colors that are not objectively there.
✗	D The brains of grapheme-color synesthetes are unusually active in the color-based region of the visual cortex.	This is true, but it leaves out an essential piece of information: namely, that this unusual activity happens when the synesthetes are reading.

	Paragraphs 5-6	Comments
P5 S1	The genetic basis of synesthesia, however, remains somewhat of a mystery.	But genetic basis is still a mystery.
2	In the early days of genetic research into the phenomenon, scientists hypothesized that the gene that brought about synesthesia was a dominant one located on the X chromosome.	Early hypothesis: dominant gene on X chromosome.
3	This was believed in part because the phenomenon appeared to be more common among women than men.	Reason.
P6 S1	This belief has changed, however, as new research has challenged it.	But new research has challenged.
2	While there does appear to be a genetic basis of some sort, as revealed by the unusual brain activity associated with the condition, several developments have undermined the hypothesis that a dominant gene on the X chromosome is the precise genetic mechanism.	Still a genetic basis, it seems, based on unusual brain activity. But some developments have weakened the early hypothesis.
3	One such development is that while early studies showed that more women than men are synesthetes, more recent and rigorous studies have suggested a more even distribution between the sexes.	Developments 1 & 2.
4	Furthermore, synesthesia can skip a generation, which means that if there is a gene for synesthesia, it cannot be a dominant gene, because dominant genes are not able to skip generations.

	Which of the following can be inferred from paragraphs 5 and 6 about the studies showing synesthesia to be more common among women than men?	Inference. P5 S3 says that some studies showed synesthesia “appeared to be more common among women than men.” P6 S3 notes that “more recent and rigorous [accurate] studies have suggested a more even distribution.” The correct answer will be a valid inference you can make about the first set of studies.
✗	A They have undermined an early hypothesis about the genetic basis of synesthesia.	This is true of the later studies that suggested a more even distribution between the sexes (P6 S2–3).
✗	B They were correct at the time, but recent population changes have made them irrelevant.	The early studies have been contradicted by more recent studies. But the passage does not suggest that population changes are the reason why the early studies are now considered inaccurate.
✓	C They seem to have not been as accurate as later studies investigating the same issue.	Correct. P6 S3: “more recent and rigorous studies have suggested a more even distribution between the sexes.” These newer studies are called “more rigorous” (the “more” carries across) and so can be trusted more. By implication, the earlier studies were not as rigorous. They reached a different conclusion because they were not as accurate, it seems.
✗	D They superseded earlier studies showing synesthesia to be evenly distributed between the sexes.	The timeline given in the passage is reversed.

	According to paragraph 5, synesthesia was once believed by researchers to be caused by	Fact. P5 S2 describes what researchers once believed about the genetic cause of synesthesia.
✗	A a gene situated on the non-dominant X chromosome	This choice incorrectly changes “dominant” to “non-dominant” and applies the adjective to the noun “X chromosome,” rather than to the noun “gene.”
✗	B a non-dominant gene present only in women’s chromosomes	The gene was thought to be dominant, not non-dominant. Also, S2 does not claim that it was only present in women’s chromosomes. It was thought to be on the X chromosome, which apparently shows up more in women (since S3 indicates that the hypothesis was supported at the time by research showing synesthesia to be more present in women). But that doesn’t mean that the gene was completely absent from men’s chromosomes.
✓	C a dominant gene that was situated on the X chromosome	Correct. P5 S2 : “scientists hypothesized that the gene that brought about synesthesia was a dominant one located on the X chromosome.”
✗	D a dominant gene not located on the X chromosome	S2 indicates that the gene was thought to be located on the X chromosome.

	According to paragraph 6, which of the following is true in general of genes that are dominant?	Fact. P6 S2 mentions dominant genes. P6 S4 mentions a fact about dominant genes in general: they cannot skip a generation.
✗	A They are not located on the X chromosome.	Recent research has called into question the hypothesis that a dominant gene on the X chromosome is the precise genetic mechanism. That doesn’t mean that no dominant genes are located on the X chromosome.
✗	B They form the genetic basis of conditions such as synesthesia.	The passage never discusses the role of dominant genes in other conditions than synesthesia.
✗	C They are more evenly distributed between the sexes than previously thought.	This is true of synesthesia (P6 S3), not of dominant genes.
✓	D They do not skip generations.	Correct. P6 S4: “dominant genes are not able to skip generations.”

P7	Paragraph 7	Comments
S1	A study of a pair of identical female twins, one of whom is synesthetic and one of whom is not, raised further questions about the genetic basis of the phenomenon.	Study of twins raised further questions. One has synesthesia, other doesn’t.
2	Identical twins have the same genetic code—all of their genes are identical.	But twins have identical genes.
3	For one to be synesthetic and the other not to be, therefore, is peculiar.
4	The study raised the possibility of whether synesthesia can be environmentally triggered or suppressed.	Can synesthesia be environmentally triggered or suppressed?
5	At the very least, it suggested there might be some explanation beyond the simple inheritance or non-inheritance of a synesthesia-causing gene.	Not a simple genetic explanation.

	According to paragraph 7, the study of the two identical twins provided reason to believe which of the following?	Fact. S4–5 outline implications of the twin study.
✓	A Environmental factors may be able to cause or at least trigger synesthesia.	Correct. S4: “The study raised the possibility of whether synesthesia can be environmentally triggered or suppressed.”
✗	B It is unlikely that synesthesia is influenced by genetic conditions.	Neither S4 nor S5 suggest that synesthesia is unlikely to be even influenced by genetic conditions. These sentences just suggest that something in addition to simple genetics seems to be at work.
✗	C The non-synesthetic twin lacked the gene for synesthesia that the other twin had.	S2: “identical twins have the same genetic code—all of their genes are identical.” So it’s not possible for one twin to lack a gene that the other one had.
✗	D Claims of synesthetic experiences by just one twin were probably mistaken.	Nothing in the paragraph indicates that the research should itself be doubted in any way.

P8	Paragraph 8	Comments
S1	But there is little evidence that synesthesia can be manipulated by one’s environment.	But you can’t environmentally manipulate synesthesia, it seems.
2	Efforts to “train” people to be synesthetes have been unsuccessful compared to actual synesthetes.	Training is unsuccessful.
3	While people can “teach” their brains to correlate certain letters with certain colors, for instance, the neural activity in their brains remains distinct from that of people who are naturally synesthetic.	Brains can be taught to do associations, but neural activity is not the same.

	The word “correlate” in the passage is closest in meaning to	VOCABULARY. “Correlate” = associate, relate to one another, gather in order to compare.
✗	A present	Unrelated. “Present” as a verb = to give formally or ceremonially (to present someone with an award).
✗	B provide	Unrelated. “Provide” = make available or supply.
✗	C repress	Unrelated. “Repress” = suppress, restrain, or prevent.
✓	D associate	Correct. “People can ‘teach’ their brains to correlate certain letters with certain colors” = people can teach their brains to associate certain letters with certain colors, or to relate them to one another.

P9	Paragraph 9	Comments
S1	A likely possibility is that the genetic basis for synesthesia does indeed lie on the X chromosome, as predicted by early researchers, and that the twin study can be explained by a phenomenon called “X-inactivation.”
2	A X-inactivation is the process by which one of a female’s two X chromosomes is rendered essentially inactive by the other X chromosome.	The inserted sentence does not make sense here, because X-inactivation has not yet been discussed.
3–4	B X-inactivation occurs randomly and at the cellular level during the earliest stages of development of the female. In other words, one X chromosome may be active in one cell (while the other one is silenced), but in the neighboring cell, the situation is reversed.	Correct. S2, the prior sentence, introduces the concept of X-inactivation. It also indicates that the phenomenon is experienced by females (“one of a female’s two X chromosomes”).
5	C This genetic phenomenon could explain the twin study, because it leads to a different expression of the same genes in two female twins, which is precisely what was observed.	This location for the sentence does not work well. First, the prior sentence (S4) does not specifically mention female experience of X-inactivation (although S3 does so). The contrast between male and female experience of the phenomenon is not drawn as sharply as it could be. Even more importantly, placing the new sentence here interrupts the flow of logic from the cellular operation of X-inactivation (S4) to how this explains the twin study (S5). So it weakens the force of the conclusion in S5.
End	D	Placement of the new sentence here undermines the necessary contrast between female and male experience of X-inactivation. Moreover, it kills the impact of the conclusion in S5, which links back to earlier paragraphs. It should be left at the very end, in order to tie up both the paragraph and the passage.

	In contrast, X-inactivation is not experienced by males, who have only one X chromosome. Where would the sentence best fit?	Insert Text. The transition phrase “In contrast” indicates that this inserted sentence should contrast with the previous sentence. The insertion states that X-inactivation is not experienced by males. So the brand-new concept of X-inactivation should be introduced before the insertion, and what is said about this concept just before the insertion should somehow indicate that X-inactivation is experienced by females.
✗	A Choice A
✓	B Choice B	Correct.
✗	C Choice C
✗	D Choice D

	Whole Passage	Comments
P1	Does the sound of music have a color to you?…	For most people, the five senses are distinct. But for synesthetes, one sense can trigger another.
2	Just how prevalent synesthesia is remains unknown…	No one knows how prevalent synesthesia is. Most common type: see letters with colors. But there are other types.
3	Other synesthetes may even have multiple forms of the condition at once…	Can even have multiple forms of synesthesia. Example. Amazing memory because his synesthesia involved all 5 senses.
4	How does synesthesia work?…	How it works. Neurological basis. Example.
5	The genetic basis of synesthesia, however, remains somewhat of a mystery…	But genetic basis is still a mystery. Early hypothesis: dominant gene on X chromosome. Reason.
6	This belief has changed, however, as new research has challenged it…	But new research has challenged. Still a genetic basis, it seems. But some developments have weakened the early hypothesis. Developments 1 & 2.
7	A study of a pair of identical female twins, one of whom is synesthetic and one of whom is not…	Study of twins raised further questions. One has synesthesia, other doesn’t. But twins have identical genes. Can synesthesia be environmentally triggered? Not a simple genetic explanation.
8	But there is little evidence that synesthesia can be manipulated by one’s environment…	But you can’t environmentally manipulate synesthesia, it seems. Training is unsuccessful. Brains can be taught to do associations, but neural activity is not the same.
9	A likely possibility is that the genetic basis for synesthesia does indeed lie on the X chromosome…	Possibility: yes, gene on X chromosome. “X-inactivation” in females = inactivation of one X at random. Can explain twin study.

	Which of the following best describes the author’s presentation of information in the passage?	Purpose. The passage first introduces synesthesia (P1–3). The rest of the passage explores the question of what causes synesthesia, which “remains somewhat of a mystery” (P5 S1), although there is a “likely possibility” (P9 S1) for the genetic basis of the condition.
✗	A A number of studies are presented to support the assertion that synesthesia is primarily an environmental phenomenon.	The passage leans the other way, offering a “likely possibility” (P9) for the genetic basis of synesthesia.
✗	B The author uses logic to show that doubt about the causes of synesthesia is unwarranted.	P5 S1: “The genetic basis of synesthesia…remains somewhat of a mystery.” Doubt remains about the causes of the condition.
✓	C The author introduces the condition of synesthesia and explores possible causes.	Correct. The introduction in P1–3 is followed by an exploration of possible causes.
✗	D Two opposing points of view about synesthesia are described; the author concludes by advocating for further research.	Opposing points of view are described (genetic vs. environmental basis for synesthesia). The author acknowledges the ongoing mystery of what causes the condition. But the author does not call for further research at the end of the passage.

	Synesthesia is a neurological phenomenon by which a small percentage of people have blended sensory experiences.	Summary. Correct answers must be clearly expressed in the passage. They must also be among the major points of the passage. They should tie as directly as possible to the summary given.
✗	a Great musicians and geniuses are often synesthetes, perceiving their medium in ways non-synesthetes cannot.	The passage gives two personal examples of synesthetes. One of them happens to be a great musician (Leonard Bernstein in P2), and the other might be classified as a genius (Solomon Shereshevsky in P3). But these examples are never generalized to any statement about “great musicians and geniuses” in relation to synesthesia.
✓	b Synesthesia manifests itself in various forms and can involve two or more senses at once.	Correct. These basic descriptions of the condition are outlined in P2–3.
✗	c The true prevalence of synesthesia is likely to continue to be unknown.	P2 mentions that the prevalence of synesthesia is unknown. But the passage does not claim that the true prevalence will remain unknown or is likely to remain unknown.
✓	d Research suggests that synesthesia may be linked to a gene located on the X chromosome.	Correct. More than one paragraph explores this possibility. Although early research is challenged, the passage concludes by stating it is likely that the gene for synesthesia is in fact located on the X chromosome, but that the phenomenon of X-inactivation prevents the expression of the gene from following typical genetic patterns.
✓	e The neurological activity of synesthetes is unusual, in a way that cannot be simulated, it seems.	Correct. P4 introduces discussion of the neurological basis of synesthesia by pointing out the “uncharacteristic neural activity” of certain synesthetes. P6 echoes the point, highlighting the importance of this unusual brain activity in supporting a genetic explanation. P8 reiterates the unusual neural activity of synesthetes and indicates that synesthesia cannot be trained or faked. The unusual brain activity associated with synesthesia is a key aspect of the condition, supporting a likely biological explanation for it.
✗	f As inherited genetic material, dominant genes are unable to skip generations.	This point is true and mentioned at the end of P6. But this fact is brought up only to support one of two challenges to the initial hypothesis about the genetic basis of synesthesia. No further elaboration is given. The point does not qualify as a main idea of this passage.