论文写作方面的经典论文

　　[This Article appeared in the American Scientist (Nov-Dec 1990), Volume 78, 550-558. Retyped and

　　posted with permission.]

　　The Science of Scientific Writing

　　If the reader is to grasp what the writer means,

　　the writer must understand what the reader needs

　　George D. Gopen and Judith A. Swan*

　　*George D. Gopen is associate professor of English and Director of Writing Programs at Duke University. He holds a Ph.D.

　　in English from Harvard University and a J.D. from Harvard Law School. Judith A. Swan teaches scientific writing at

　　Princeton University. Her Ph.D., which is in biochemistry, was earned at the Massachusetts Institute of Technology. Address

　　for Gopen: 307 Allen Building, Duke University, Durham, NC 27706

　　Science is often hard to read. Most people assume that its difficulties are born out of necessity, out of

　　the extreme complexity of scientific concepts, data and analysis. We argue here that complexity of

　　thought need not lead to impenetrability of expression; we demonstrate a number of rhetorical principles

　　that can produce clarity in communication without oversimplifying scientific issues. The results are

　　substantive, not merely cosmetic: Improving the quality of writing actually improves the quality of

　　thought.

　　The fundamental purpose of scientific discourse is not the mere presentation of information and thought,

　　but rather its actual communication. It does not matter how pleased an author might be to have

　　converted all the right data into sentences and paragraphs; it matters only whether a large majority of the

　　reading audience accurately perceives what the author had in mind. Therefore, in order to understand

　　how best to improve writing, we would do well to understand better how readers go about reading. Such

　　an understanding has recently become available through work done in the fields of rhetoric, linguistics

　　and cognitive psychology. It has helped to produce a methodology based on the concept of reader

　　expectations.

　　Writing with the Reader in Mind: Expectation and Context

　　Readers do not simply read; they interpret. Any piece of prose, no matter how short, may "mean" in 10

　　(or more) different ways to 10 different readers. This methodology of reader expectations is founded on

　　the recognition that readers make many of their most important interpretive decisions about the

　　substance of prose based on clues they receive from its structure.

　　This interplay between substance and structure can be demonstrated by something as basic as a simple

　　table. Let us say that in tracking the temperature of a liquid over a period of time, an investigator takes

　　measurements every three minutes and records a list of temperatures. Those data could be presented by a

　　number of written structures. Here are two possibilities:

　　t(time)=15’, T(temperature)=32º, t=0’, T=25º;

　　t=6’, T=29º; t=3’, T=27º; t=12’, T=32º; t=9’;

　　T=31º

　　time (min) temperature(ºC)

　　0 25

　　3 27

　　6 29

　　9 31

　　12 32

　　15 32

　　Precisely the same information appears in both formats, yet most readers find the second easier to

　　interpret. It may be that the very familiarity of the tabular structure makes it easier to use. But, more

　　significantly, the structure of the second table provides the reader with an easily perceived context (time)

　　in which the significant piece of information (temperature) can be interpreted. The contextual material

　　appears on the left in a pattern that produces an expectation of regularity; the interesting results appear

　　on the right in a less obvious pattern, the discovery of which is the point of the table.

　　If the two sides of this simple table are reversed, it becomes much harder to read.

　　temperature(ºC) time(min)

　　25 0

　　27 3

　　29 6

　　31 9

　　32 12

　　32 15

　　Since we read from left to right, we prefer the context on the left, where it can more effectively

　　familiarize the reader. We prefer the new, important information on the right, since its job is to intrigue

　　the reader.

　　Information is interpreted more easily and more uniformly if it is placed where most readers expect to

　　find it. These needs and expectations of readers affect the interpretation not only of tables and

　　illustrations but also of prose itself. Readers have relatively fixed expectations about where in the

　　structure of prose they will encounter particular items of its substance. If writers can become

　　consciously aware of these locations, they can better control the degrees of recognition and emphasis a

　　reader will give to the various pieces of information being presented. Good writers are intuitively aware

　　of these expectations; that is why their prose has what we call "shape."

　　This underlying concept of reader expectation is perhaps most immediately evident at the level of the

　　largest units of discourse. (A unit of discourse is defined as anything with a beginning and an end: a

　　clause, a sentence, a section, an article, etc.) A research article, for example, is generally divided into

　　recognizable sections, sometimes labeled Introduction, Experimental Methods, Results and Discussion.

　　When the sections are confused--when too much experimental detail is found in the Results section, or

　　when discussion and results intermingle--readers are often equally confused. In smaller units of

　　discourse the functional divisions are not so explicitly labeled, but readers have definite expectations all

　　the same, and they search for certain information in particular places. If these structural expectations are

　　continually violated, readers are forced to divert energy from understanding the content of a passage to

　　unraveling its structure. As the complexity of the context increases moderately, the possibility of

　　misinterpretation or noninterpretation increases dramatically.

　　We present here some results of applying this methodology to research reports in the scientific literature.

　　We have taken several passages from research articles (either published or accepted for publication) and

　　have suggested ways of rewriting them by applying principles derived from the study of reader

　　expectations. We have not sought to transform. the passages into "plain English" for the use of the

　　general public; we have neither decreased the jargon nor diluted the science. We have striven not for

　　simplification but for clarification.

　　Reader Expectations for the Structure of Prose

　　Here is our first example of scientific prose, in its original form.:

　　The smallest of the URF’s (URFA6L), a 207-nucleotide (nt) reading frame. overlapping out of

　　phase the NH2-terminal portion of the adenosinetriphosphatase (ATPase) subunit 6 gene has been

　　identified as the animal equivalent of the recently discovered yeast H+-ATPase subunit 8 gene.

　　The functional significance of the other URF’s has been, on the contrary, elusive. Recently,

　　however, immunoprecipitation experiments with antibodies to purified, rotenone-sensitive

　　NADH-ubiquinone oxido-reductase [hereafter referred to as respiratory chain NADH

　　dehydrogenase or complex I] from bovine heart, as well as enzyme fractionation studies, have

　　indicated that six human URF’s (that is, URF1, URF2, URF3, URF4, URF4L, and URF5,

　　hereafter referred to as ND1, ND2, ND3, ND4, ND4L, and ND5) encode subunits of complex I.

　　This is a large complex that also contains many subunits synthesized in the cytoplasm.*

　　[*The full paragraph includes one more sentence: "Support for such functional identification of the URF products has come

　　from the finding that the purified rotenone-sensitive NADH dehydrogenase from Neurospora crassa contains several

　　subunits synthesized within the mitochondria, and from the observation that the stopper mutant of Neurospora crassa, whose

　　mtDNA lacks two genes homologous to URF2 and URF3, has no functional complex I." We have omitted this sentence both

　　because the passage is long enough as is and because it raises no additional structural issues.]

　　Ask any ten people why this paragraph is hard to read, and nine are sure to mention the technical

　　vocabulary; several will also suggest that it requires specialized background knowledge. Those problems

　　turn out to be only a small part of the difficulty. Here is the passage again, with the difficult words

　　temporarily lifted:

　　The smallest of the URF’s, and [A], has been identified as a [B] subunit 8 gene. The functional

　　significance of the other URF’s has been, on the contrary, elusive. Recently, however, [C]

　　experiments, as well as [D] studies, have indicated that six human URF’s [1-6] encode subunits of

　　Complex I. This is a large complex that also contains many subunits synthesized in the cytoplasm.

　　It may now be easier to survive the journey through the prose, but the passage is still difficult. Any

　　number of questions present themselves: What has the first sentence of the passage to do with the last

　　sentence? Does the third sentence contradict what we have been told in the second sentence? Is the

　　functional significance of URF’s still "elusive"? Will this passage lead us to further discussion about

　　URF’s, or about Complex I, or both?

　　Information is interpreted more easily and more

　　uniformly if it is placed where most readers expect

　　to find it.

　　Knowing a little about the subject matter does not clear up all the confusion. The intended audience of

　　this passage would probably possess at least two items of essential technical information: first, "URF"

　　stands for "Uninterrupted Reading Frame," which describes a segment of DNA organized in such a way

　　that it could encode a protein, although no such protein product has yet been identified; second, both

　　APTase and NADH oxido-reductase are enzyme complexes central to energy metabolism. Although this

　　information may provide some sense of comfort, it does little to answer the interpretive questions that

　　need answering. It seems the reader is hindered by more than just the scientific jargon.

　　To get at the problem, we need to articulate something about how readers go about reading. We proceed

　　to the first of several reader expectations.

　　Subject-Verb Separation

　　Look again at the first sentence of the passage cited above. It is relatively long, 42 words; but that turns

　　out not to be the main cause of its burdensome complexity. Long sentences need not be difficult to read;

　　they are only difficult to write. We have seen sentences of over 100 words that flow easily and

　　persuasively toward their clearly demarcated destination. Those well-wrought serpents all had

　　something in common: Their structure presented information to readers in the order the readers needed

　　and expected it.

　　Beginning with the exciting material and ending

　　with a lack of luster often leaves us disappointed

　　and destroys our sense of momentum.

　　The first sentence of our example passage does just the opposite: it burdens and obstructs the reader,

　　because of an all-too-common structural defect. Note that the grammatical subject ("the smallest") is

　　separated from its verb ("has been identified") by 23 words, more than half the sentence. Readers expect

　　a grammatical subject to be followed immediately by the verb. Anything of length that intervenes

　　between subject and verb is read as an interruption, and therefore as something of lesser importance.

　　The reader’s expectation stems from a pressing need for syntactic resolution, fulfilled only by the arrival

　　of the verb. Without the verb, we do not know what the subject is doing, or what the sentence is all

　　about. As a result, the reader focuses attention on the arrival of the verb and resists recognizing anything

　　in the interrupting material as being of primary importance. The longer the interruption lasts, the more

　　likely it becomes that the "interruptive" material actually contains important information; but its

　　structural location will continue to brand it as merely interruptive. Unfortunately, the reader will not

　　discover its true value until too late-until the sentence has ended without having produced anything of

　　much value outside of that subject-verb interruption.

　　In this first sentence of the paragraph, the relative importance of the intervening material is difficult to

　　evaluate. The material might conceivably be quite significant, in which case the writer should have

　　positioned it to reveal that importance. Here is one way to incorporate it into the sentence structure:

　　The smallest of the URF’s is URFA6L, a 207-nucleotide (nt) reading frame. overlapping out of

　　phase the NH2-terminal portion of the adenosinetriphosphatase (ATPase) subunit 6 gene; it has

　　been identified as the animal equivalent of the recently discovered yeast H+-ATPase subunit 8

　　gene.

　　On the other hand, the intervening material might be a mere aside that diverts attention from more

　　important ideas; in that case the writer should have deleted it, allowing the prose to drive more directly

　　toward its significant point:

　　The smallest of the URF’s (URFA6L) has been identified as the animal equivalent of the recently

　　discovered yeast H+-ATPase subunit 8 gene.

　　Only the author could tell us which of these revisions more accurately reflects his intentions.

　　These revisions lead us to a second set of reader expectations. Each unit of discourse, no matter what the

　　size, is expected to serve a single function, to make a single point. In the case of a sentence, the point is

　　expected to appear in a specific place reserved for emphasis.

　　The Stress Position

　　It is a linguistic commonplace that readers naturally emphasize the material that arrives at the end of a

　　sentence. We refer to that location as a "stress position." If a writer is consciously aware of this

　　tendency, she can arrange for the emphatic information to appear at the moment the reader is naturally

　　exerting the greatest reading emphasis. As a result, the chances greatly increase that reader and writer

　　will perceive the same material as being worthy of primary emphasis. The very structure of the sentence

　　thus helps persuade the reader of the relative values of the sentence’s contents.

　　The inclination to direct more energy to that which arrives last in a sentence seems to correspond to the

　　way we work at tasks through time. We tend to take something like a "mental breath" as we begin to

　　read each new sentence, thereby summoning the tension with which we pay attention to the unfolding of

　　the syntax. As we recognize that the sentence is drawing toward its conclusion, we begin to exhale that

　　mental breath. The exhalation produces a sense of emphasis. Moreover, we delight in being rewarded at

　　the end of a labor with something that makes the ongoing effort worthwhile. Beginning with the exciting

　　material and ending with a lack of luster often leaves us disappointed and destroys our sense of

　　momentum. We do not start with the strawberry shortcake and work our way up to the broccoli.

　　When the writer puts the emphatic material of a sentence in any place other than the stress position, one

　　of two things can happen; both are bad. First, the reader might find the stress position occupied by

　　material that clearly is not worthy of emphasis. In this case, the reader must discern, without any

　　additional structural clue, what else in the sentence may be the most likely candidate for emphasis.

　　There are no secondary structural indications to fall back upon. In sentences that are long, dense or

　　sophisticated, chances soar that the reader will not interpret the prose precisely as the writer intended.

　　The second possibility is even worse: The reader may find the stress position occupied by something

　　that does appear capable of receiving emphasis, even though the writer did not intend to give it any

　　stress. In that case, the reader is highly likely to emphasize this imposter material, and the writer will

　　have lost an important opportunity to influence the reader’s interpretive process.

　　The stress position can change in size from sentence to sentence. Sometimes it consists of a single word;

　　sometimes it extends to several lines. The definitive factor is this: The stress position coincides with the

　　moment of syntactic closure. A reader has reached the beginning of the stress position when she knows

　　there is nothing left in the clause or sentence but the material presently being read. Thus a whole list,

　　numbered and indented, can occupy the stress position of a sentence if it has been clearly announced as

　　being all that remains of that sentence. Each member of that list, in turn, may have its own internal stress

　　position, since each member may produce its own syntactic closure.

　　Within a sentence, secondary stress positions can be formed by the appearance of a properly used colon

　　or semicolon; by grammatical convention, the material preceding these punctuation marks must be able

　　to stand by itself as a complete sentence. Thus, sentences can be extended effortlessly to dozens of

　　words, as long as there is a medial syntactic closure for every piece of new, stress-worthy information

　　along the way. One of our revisions of the initial sentence can serve as an example:

　　The smallest of the URF’s is URFA6L, a 207-nucleotide (nt) reading frame. overlapping out of

　　phase the NH2-terminal portion of the adenosinetriphosphatase (ATPase) subunit 6 gene; it has

　　been identified as the animal equivalent of the recently discovered yeast H+-ATPase subunit 8

　　gene.

　　By using a semicolon, we created a second stress position to accommodate a second piece of

　　information that seemed to require emphasis.

　　We now have three rhetorical principles based on reader expectations: First, grammatical subjects

　　should be followed as soon as possible by their verbs; second, every unit of discourse, no matter the

　　size, should serve a single function or make a single point; and, third, information intended to be

　　emphasized should appear at points of syntactic closure. Using these principles, we can begin to unravel

　　the problems of our example prose.

　　Note the subject-verb separation in the 62-word third sentence of the original passage:

　　Recently, however, immunoprecipitation experiments with antibodies to purified,

　　rotenone-sensitive NADH-ubiquinone oxido-reductase [hereafter referred to as respiratory chain

　　NADH dehydrogenase or complex I] from bovine heart, as well as enzyme fractionation studies,

　　have indicated that six human URF’s (that is, URF1, URF2, URF3, URF4, URF4L, and URF5,

　　hereafter referred to as ND1, ND2, ND3, ND4, ND4L and ND5) encode subunits of complex I.

　　After encountering the subject ("experiments"), the reader must wade through 27 words (including three

　　hyphenated compound words, a parenthetical interruption and an "as well as" phrase) before alighting on

　　the highly uninformative and disappointingly anticlimactic verb ("have indicated"). Without a moment

　　to recover, the reader is handed a "that" clause in which the new subject ("six human URF’s") is

　　separated from its verb ("encode") by yet another 20 words.

　　If we applied the three principles we have developed to the rest of the sentences of the example, we

　　could generate a great many revised versions of each. These revisions might differ significantly from

　　one another in the way their structures indicate to the reader the various weights and balances to be

　　given to the information. Had the author placed all stress-worthy material in stress positions, we as a

　　reading community would have been far more likely to interpret these sentences uniformly.

　　We couch this discussion in terms of "likelihood" because we believe that meaning is not inherent in

　　discourse by itself; "meaning" requires the combined participation of text and reader. All sentences are

　　infinitely interpretable, given an infinite number of interpreters. As communities of readers, however,

　　we tend to work out tacit agreements as to what kinds of meaning are most likely to be extracted from

　　certain articulations. We cannot succeed in making even a single sentence mean one and only one thing;

　　we can only increase the odds that a large majority of readers will tend to interpret our discourse

　　according to our intentions. Such success will follow from authors becoming more consciously aware of

　　the various reader expectations presented here.

　　We cannot succeed in making even a single

　　sentence mean one and only one thing; we can only

　　increase the odds that a large majority of readers

　　will tend to interpret our discourse according to our

　　intentions.

　　Here is one set of revisionary decisions we made for the example:

　　The smallest of the URF’s, URFA6L, has been identified as the animal equivalent of the recently

　　discovered yeast H+-ATPase subunit 8 gene; but the functional significance of other URF’s has

　　been more elusive. Recently, however, several human URF’s have been shown to encode subunits

　　of rotenone-sensitive NADH-ubiquinone oxido-reductase. This is a large complex that also

　　contains many subunits synthesized in the cytoplasm; it will be referred to hereafter as respiratory

　　chain NADH dehydrogenase or complex I. Six subunits of Complex I were shown by enzyme

　　fractionation studies and immunoprecipitation experiments to be encoded by six human URF’s

　　(URF1, URF2, URF3, URF4, URF4L, and URF5); these URF’s will be referred to subsequently as

　　ND1, ND2, ND3, ND4, ND4L and ND5.

　　Sheer length was neither the problem nor the solution. The revised version is not noticeably shorter than

　　the original; nevertheless, it is significantly easier to interpret. We have indeed deleted certain words,

　　but not on the basis of wordiness or excess length. (See especially the last sentence of our revision.)

　　When is a sentence too long? The creators of readability formulas would have us believe there exists

　　some fixed number of words (the favorite is 29) past which a sentence is too hard to read. We disagree.

　　We have seen 10-word sentences that are virtually impenetrable and, as we mentioned above, 100-word

　　sentences that flow effortlessly to their points of resolution. In place of the word-limit concept, we offer

　　the following definition: A sentence is too long when it has more viable candidates for stress positions

　　than there are stress positions available. Without the stress position’s locational clue that its material is

　　intended to be emphasized, readers are left too much to their own devices in deciding just what else in a

　　sentence might be considered important.

　　In revising the example passage, we made certain decisions about what to omit and what to emphasize.

　　We put subjects and verbs together to lessen the reader’s syntactic burdens; we put the material we

　　believed worthy of emphasis in stress positions; and we discarded material for which we could not

　　discern significant connections. In doing so, we have produced a clearer passage--but not one that

　　necessarily reflects the author’s intentions; it reflects only our interpretation of the author’s intentions.

　　The more problematic the structure, the less likely it becomes that a grand majority of readers will

　　perceive the discourse in exactly the way the author intended.

　　The information that begins a sentence establishes

　　for the reader a perspective for viewing the

　　sentence as a unit.

　　It is probable that many of our readers--and perhaps even the authors--will disagree with some of our

　　choices. If so, that disagreement underscores our point: The original failed to communicate its ideas and

　　their connections clearly. If we happened to have interpreted the passage as you did, then we can make a

　　different point: No one should have to work as hard as we did to unearth the content of a single passage

　　of this length.

　　The Topic Position

　　To summarize the principles connected with the stress position, we have the proverbial wisdom, "Save

　　the best for last." To summarize the principles connected with the other end of the sentence, which we

　　will call the topic position, we have its proverbial contradiction, "First things first." In the stress position

　　the reader needs and expects closure and fulfillment; in the topic position the reader needs and expects

　　perspective and context. With so much of reading comprehension affected by what shows up in the topic

　　position, it behooves a writer to control what appears at the beginning of sentences with great care.

　　The information that begins a sentence establishes for the reader a perspective for viewing the sentence

　　as a unit: Readers expect a unit of discourse to be a story about whoever shows up first. "Bees disperse

　　pollen" and "Pollen is dispersed by bees" are two different but equally respectable sentences about the

　　same facts. The first tells us something about bees; the second tells us something about pollen. The

　　passivity of the second sentence does not by itself impair its quality; in fact, "Pollen is dispersed by

　　bees" is the superior sentence if it appears in a paragraph that intends to tell us a continuing story about

　　pollen. Pollen’s story at that moment is a passive one.

　　Readers also expect the material occupying the topic position to provide them with linkage (looking

　　backward) and context (looking forward). The information in the topic position prepares the reader for

　　upcoming material by connecting it backward to the previous discussion. Although linkage and context

　　can derive from several sources, they stem primarily from material that the reader has already

　　encountered within this particular piece of discourse. We refer to this familiar, previously introduced

　　material as "old information." Conversely, material making its first appearance in a discourse is "new

　　information." When new information is important enough to receive emphasis, it functions best in the

　　stress position.

　　When old information consistently arrives in the topic position, it helps readers to construct the logical

　　flow of the argument: It focuses attention on one particular strand of the discussion, both harkening

　　backward and leaning forward. In contrast, if the topic position is constantly occupied by material that

　　fails to establish linkage and context, readers will have difficulty perceiving both the connection to the

　　previous sentence and the projected role of the new sentence in the development of the paragraph as a

　　whole.

　　Here is a second example of scientific prose that we shall attempt to improve in subsequent discussion:

　　Large earthquakes along a given fault segment do not occur at random intervals because it takes

　　time to accumulate the strain energy for the rupture. The rates at which tectonic plates move and

　　accumulate strain at their boundaries are approximately uniform. Therefore, in first approximation,

　　one may expect that large ruptures of the same fault segment will occur at approximately constant

　　time intervals. If subsequent main shocks have different amounts of slip across the fault, then the

　　recurrence time may vary, and the basic idea of periodic mainshocks must be modified. For great

　　plate boundary ruptures the length and slip often vary by a factor of 2. Along the southern segment

　　of the San Andreas fault the recurrence interval is 145 years with variations of several decades.

　　The smaller the standard deviation of the average recurrence interval, the more specific could be

　　the long term prediction of a future mainshock.

　　This is the kind of passage that in subtle ways can make readers feel badly about themselves. The

　　individual sentences give the impression of being intelligently fashioned: They are not especially long or

　　convoluted; their vocabulary is appropriately professional but not beyond the ken of educated general

　　readers; and they are free of grammatical and dictional errors. On first reading, however, many of us

　　arrive at the paragraph’s end without a clear sense of where we have been or where we are going. When

　　that happens, we tend to berate ourselves for not having paid close enough attention. In reality, the fault

　　lies not with us, but with the author.

　　We can distill the problem by looking closely at the information in each sentence’s topic position:

　　Large earthquakes

　　The rates

　　Therefore...one

　　subsequent mainshocks

　　great plate boundary ruptures

　　the southern segment of the San Andreas fault

　　the smaller the standard deviation...

　　Much of this information is making its first appearance in this paragraph--in precisely the spot where the

　　reader looks for old, familiar information. As a result, the focus of the story constantly shifts. Given just

　　the material in the topic positions, no two readers would be likely to construct exactly the same story for

　　the paragraph as a whole.

　　If we try to piece together the relationship of each sentence to its neighbors, we notice that certain bits of

　　old information keep reappearing. We hear a good deal about the recurrence time between earthquakes:

　　The first sentence introduces the concept of nonrandom intervals between earthquakes; the second

　　sentence tells us that recurrence rates due to the movement of tectonic plates are more or less uniform;

　　the third sentence adds that the recurrence rates of major earthquakes should also be somewhat

　　predictable; the fourth sentence adds that recurrence rates vary with some conditions; the fifth sentence

　　adds information about one particular variation; the sixth sentence adds a recurrence-rate example from

　　California; and the last sentence tells us something about how recurrence rates can be described

　　statistically. This refrain of "recurrence intervals" constitutes the major string of old information in the

　　paragraph. Unfortunately, it rarely appears at the beginning of sentences, where it would help us

　　maintain our focus on its continuing story.

　　In reading, as in most experiences, we appreciate the opportunity to become familiar with a new

　　environment before having to function in it. Writing that continually begins sentences with new

　　information and ends with old information forbids both the sense of comfort and orientation at the start

　　and the sense of fulfilling arrival at the end. It misleads the reader as to whose story is being told; it

　　burdens the reader with new information that must be carried further into the sentence before it can be

　　connected to the discussion; and it creates ambiguity as to which material the writer intended the reader

　　to emphasize. All of these distractions require that readers expend a disproportionate amount of energy

　　to unravel the structure of the prose, leaving less energy available for perceiving content.

　　We can begin to revise the example by ensuring the following for each sentence:

　　1. The backward-linking old information appears in the topic position.

　　2. The person, thing or concept whose story it is appears in the topic position.

　　3. The new, emphasis-worthy information appears in the stress position.

　　Once again, if our decisions concerning the relative values of specific information differ from yours, we

　　can all blame the author, who failed to make his intentions apparent. Here first is a list of what we

　　perceived to be the new, emphatic material in each sentence:

　　time to accumulate strain energy along a fault

　　approximately uniform

　　large ruptures of the same fault

　　different amounts of slip

　　vary by a factor of 2

　　variations of several decades

　　predictions of future mainshock

　　Now, based on these assumptions about what deserves stress, here is our proposed revision:

　　Large earthquakes along a given fault segment do not occur at random intervals because it takes

　　time to accumulate the strain energy for the rupture. The rates at which tectonic plates move and

　　accumulate strain at their boundaries are roughly uniform. Therefore, nearly constant time

　　intervals (at first approximation) would be expected between large ruptures of the same fault

　　segment. [However?], the recurrence time may vary; the basic idea of periodic mainshocks may

　　need to be modified if subsequent mainshocks have different amounts of slip across the fault.

　　[Indeed?], the length and slip of great plate boundary ruptures often vary by a factor of 2. [For

　　example?], the recurrence intervals along the southern segment of the San Andreas fault is 145

　　years with variations of several decades. The smaller the standard deviation of the average

　　recurrence interval, the more specific could be the long term prediction of a future mainshock.

　　Many problems that had existed in the original have now surfaced for the first time. Is the reason

　　earthquakes do not occur at random intervals stated in the first sentence or in the second? Are the

　　suggested choices of "however," "indeed," and "for example" the right ones to express the connections

　　at those points? (All these connections were left unarticulated in the original paragraph.) If "for

　　example" is an inaccurate transitional phrase, then exactly how does the San Andreas fault example

　　connect to ruptures that "vary by a factor of 2"? Is the author arguing that recurrence rates must vary

　　because fault movements often vary? Or is the author preparing us for a discussion of how in spite of

　　such variance we might still be able to predict earthquakes? This last question remains unanswered

　　because the final sentence leaves behind earthquakes that recur at variable intervals and switches instead

　　to earthquakes that recur regularly. Given that this is the first paragraph of the article, which type of

　　earthquake will the article most likely proceed to discuss? In sum, we are now aware of how much the

　　paragraph had not communicated to us on first reading. We can see that most of our difficulty was

　　owing not to any deficiency in our reading skills but rather to the author’s lack of comprehension of our

　　structural needs as readers.

　　In our experience, the misplacement of old and

　　new information turns out to be he No. 1 problem in

　　American professional writing today.

　　In our experience, the misplacement of old and new information turns out to be the No. 1 problem in

　　American professional writing today. The source of the problem is not hard to discover: Most writers

　　produce prose linearly (from left to right) and through time. As they begin to formulate a sentence, often

　　their primary anxiety is to capture the important new thought before it escapes. Quite naturally they rush

　　to record that new information on paper, after which they can produce at their leisure contextualizing

　　material that links back to the previous discourse. Writers who do this consistently are attending more to

　　their own need for unburdening themselves of their information than to the reader’s need for receiving

　　the material. The methodology of reader expectations articulates the reader’s needs explicitly, thereby

　　making writers consciously aware of structural problems and ways to solve them.

　　Put in the topic position the old information that

　　links backward; put in the stress position the new

　　information you want the reader to emphasize.

　　A note of clarification: Many people hearing this structural advice tend to oversimplify it to the

　　following rule: "Put the old information in the topic position and the new information in the stress

　　position." No such rule is possible. Since by definition all information is either old or new, the space

　　between the topic position and the stress position must also be filled with old and new information.

　　Therefore the principle (not rule) should be stated as follows: "Put in the topic position the old

　　information that links backward; put in the stress position the new information you want the reader to

　　emphasize."

　　Perceiving Logical Gaps

　　When old information does not appear at all in a sentence, whether in the topic position or elsewhere,

　　readers are left to construct the logical linkage by themselves. Often this happens when the connections

　　are so clear in the writer’s mind that they seem unnecessary to state; at those moments, writers

　　underestimate the difficulties and ambiguities inherent in the reading process. Our third example

　　attempts to demonstrate how paying attention to the placement of old and new information can reveal

　　where a writer has neglected to articulate essential connections.

　　The enthalpy of hydrogen bond formation between the nucleoside bases 2’deoxyguanosine (dG)

　　and 2’deoxycytidine (dC) has been determined by direct measurement. dG and dC were

　　derivatized at the 5’ and 3’ hydroxyls with triisopropylsilyl groups to obtain solubility of the

　　nucleosides in non-aqueous solvents and to prevent the ribose hydroxyls from forming hydrogen

　　bonds. From isoperibolic titration measurements, the enthalpy of dC:dG base pair formation is

　　-6.65±0.32 kcal/mol.

　　Although part of the difficulty of reading this passage may stem from its abundance of specialized

　　technical terms, a great deal more of the difficulty can be attributed to its structural problems. These

　　problems are now familiar: We are not sure at all times whose story is being told; in the first sentence

　　the subject and verb are widely separated; the second sentence has only one stress position but two or

　　three pieces of information that are probably worthy of emphasis--"solubility ...solvents," "prevent...

　　from forming hydrogen bonds" and perhaps "triisopropylsilyl groups." These perceptions suggest the

　　following revision tactics:

　　1. Invert the first sentence, so that (a) the subject-verb-complement connection is unbroken, and (b)

　　"dG" and "dC" are introduced in the stress position as new and interesting information. (Note that

　　inverting the sentence requires stating who made the measurement; since the authors performed

　　the first direct measurement, recognizing their agency in the topic position may well be

　　appropriate.)

　　2. Since "dG and "dC" become the old information in the second sentence, keep them up front in the

　　topic position.

　　3. Since "triisopropylsilyl groups" is new and important information here, create for it a stress

　　position.

　　4. "Triisopropylsilyl groups" then becomes the old information of the clause in which its effects are

　　described; place it in the topic position of this clause.

　　5. Alert the reader to expect the arrival of two distinct effects by using the flag word "both." "Both"

　　notifies the reader that two pieces of new information will arrive in a single stress position.

　　Here is a partial revision based on these decisions:

　　We have directly measured the enthalpy of hydrogen bond formation between the nucleoside bases

　　2’deoxyguanosine (dG) and 2’deoxycytidine (dC). dG and dC were derivatized at the 5’ and 3’

　　hydroxyls with triisopropylsilyl groups; these groups serve both to solubilize the nucleosides in

　　non-aqueous solvents and to prevent the ribose hydroxyls from forming hydrogen bonds. From

　　isoperibolic titration measurements, the enthalpy of dC:dG base pair formation is -6.65±0.32

　　kcal/mol.

　　The outlines of the experiment are now becoming visible, but there is still a major logical gap. After

　　reading the second sentence, we expect to hear more about the two effects that were important enough to

　　merit placement in its stress position. Our expectations are frustrated, however, when those effects are

　　not mentioned in the next sentence: "From isoperibolic titration measurements, the enthalpy of dC:dG

　　base pair formation is -6.65±0.32 kcal/mol." The authors have neglected to explain the relationship

　　between the derivatization they performed (in the second sentence) and the measurements they made (in

　　the third sentence). Ironically, that is the point they most wished to make here.

　　At this juncture, particularly astute readers who are chemists might draw upon their specialized

　　knowledge, silently supplying the missing connection. Other readers are left in the dark. Here is one

　　version of what we think the authors meant to say, with two additional sentences supplied from a

　　knowledge of nucleic acid chemistry:

　　We have directly measured the enthalpy of hydrogen bond formation between the nucleoside bases

　　2’deoxyguanosine (dG) and 2’deoxycytidine (dC). dG and dC were derivatized at the 5’ and 3’

　　hydroxyls with triisopropylsiyl groups; these groups serve both to solubilize the nucleosides in

　　non-aqueous solvents and to prevent the ribose hydroxyls from forming hydrogen bonds.

　　Consequently, when the derivatized nucleosides are dissolved in non-aqueous solvents, hydrogen

　　bonds form. almost exclusively between the bases. Since the interbase hydrogen bonds are the only

　　bonds to form. upon mixing, their enthalpy of formation can be determined directly by measuring

　　the enthalpy of mixing. From our isoperibolic titration measurements, the enthalpy of dG:dC base

　　pair formation is -6.65±0.32 kcal/mol.

　　Each sentence now proceeds logically from its predecessor. We never have to wander too far into a

　　sentence without being told where we are and what former strands of discourse are being continued.

　　And the "measurements" of the last sentence has now become old information, reaching back to the

　　"measured directly" of the preceding sentence. (It also fulfills the promise of the "we have directly

　　measured" with which the paragraph began.) By following our knowledge of reader expectations, we

　　have been able to spot discontinuities, to suggest strategies for bridging gaps, and to rearrange the

　　structure of the prose, thereby increasing the accessibility of the scientific content.

　　Locating the Action

　　Our final example adds another major reader expectation to the list.

　　Transcription of the 5S RNA genes in the egg extract is TFIIIA-dependent. This is surprising,

　　because the concentration of TFIIIA is the same as in the oocyte nuclear extract. The other

　　transcription factors and RNA polymerase III are presumed to be in excess over available TFIIIA,

　　because tRNA genes are transcribed in the egg extract. The addition of egg extract to the oocyte

　　nuclear extract has two effects on transcription efficiency. First, there is a general inhibition of

　　transcription that can be alleviated in part by supplementation with high concentrations of RNA

　　polymerase III. Second, egg extract destabilizes transcription complexes formed with oocyte but

　　not somatic 5S RNA genes.

　　The barriers to comprehension in this passage are so many that it may appear difficult to know where to

　　start revising. Fortunately, it does not matter where we start, since attending to any one structural

　　problem eventually leads us to all the others.

　　We can spot one source of difficulty by looking at the topic positions of the sentences: We cannot tell

　　whose story the passage is. The story’s focus (that is, the occupant of the topic position) changes in

　　every sentence. If we search for repeated old information in hope of settling on a good candidate for

　　several of the topic positions, we find all too much of it: egg extract, TFIIIA, oocyte extract, RNA

　　polymerase III, 5S RNA, and transcription. All of these reappear at various points, but none announces

　　itself clearly as our primary focus. It appears that the passage is trying to tell several stories

　　simultaneously, allowing none to dominate.

　　We are unable to decide among these stories because the author has not told us what to do with all this

　　information. We know who the players are, but we are ignorant of the actions they are presumed to

　　perform. This violates yet another important reader expectation: Readers expect the action of a sentence

　　to be articulated by the verb.

　　Here is a list of the verbs in the example paragraph:

　　is

　　is...is

　　are presumed to be

　　are transcribed

　　has

　　is...can be alleviated

　　destabilizes

　　The list gives us too few clues as to what actions actually take place in the passage. If the actions are not

　　to be found in the verbs, then we as readers have no secondary structural clues for where to locate them.

　　Each of us has to make a personal interpretive guess; the writer no longer controls the reader’s

　　interpretive act.

　　As critical scientific readers, we would like to

　　concentrate our energy on whether the experiments

　　prove the hypotheses.

　　Worse still, in this passage the important actions never appear. Based on our best understanding of this

　　material, the verbs that connect these players are "limit" and "inhibit." If we express those actions as

　　verbs and place the most frequently occurring information--"egg extract" and "TFIIIA"--in the topic

　　position whenever possible,* we can generate the following revision:

　　In the egg extract, the availability of TFIIIA limits transcription of the 5S RNA genes. This is

　　surprising because the same concentration of TFIIIA does not limit transcription in the oocyte

　　nuclear extract. In the egg extract, transcription is not limited by RNA polymerase or other factors

　　because transcription of tRNA genes indicates that these factors are in excess over available

　　TFIIIA. When added to the nuclear extract, the egg extract affected the efficiency of transcription

　　in two ways. First, it inhibited transcription generally; this inhibition could be alleviated in part by

　　supplementing the mixture with high concentrations of RNA polymerase III. Second, the egg

　　extract destabilized transcription complexes formed by oocyte but not by somatic 5S genes.

　　[*We have chosen these two pieces of old information as the controlling contexts for the passage. That choice was neither

　　arbitrary nor born of logical necessity; it was simply an act of interpretation. All readers make exactly that kind of choice in

　　the reading of every sentence. The fewer the structural clues to interpretation given by the author, the more variable the

　　resulting interpretations will tend to be.]

　　As a story about "egg extract," this passage still leaves something to be desired. But at lea