science

Two large-scale international studies have become established to compare countries' performance in the core subjects of literacy, mathematics and science.

TIMSS: Trends in International Mathematics and Science Study

TIMSS is an international study involving 50 countries that assesses math and science achievement at four year intervals. It has been running since 1995. Students are assessed in the 4th and 8th years of school, and in their final year. The next assessment round will be in 2007.

The study uses four benchmarks (advanced, high, intermediate, low) to gather a more complete picture of trends within a country. Thus we can not only approve high performing countries like Singapore, Chinese Taipei, Korea, and Hong Kong, for having about 1/3 or more of their 8th grade students reach the advanced benchmark in mathematics, and about 2/3 to 3/4 reaching the high benchmark, but we can also note, for example, that although the Netherlands doesn't have high numbers reaching the advanced level (some 10% of 8th graders and 5% of 4th graders), it does at least do an excellent job of educating all its students, since 97% of its 8th graders and 99% of its 4th graders reach the low benchmark. It also enables us to spot trends across time — for example, in general, countries have improved their levels at the lower end, but not at the high end.

Mathematics

Grade 8 Advanced Benchmark

Students can organize information, make generalizations, solve non-routine problems, and draw and justify conclusions from data. They can compute percent change and apply their knowledge of numeric and algebraic concepts and relationships to solve problems. Students can solve simultaneous linear equations and model simple situations algebraically. They can apply their knowledge of measurement and geometry in complex problem situations. They can interpret data from a variety of tables and graphs, including interpolation and extrapolation.

Grade 8 High Benchmark

Students can apply their understanding and knowledge in a wide variety of relatively complex situations. They can order, relate, and compute with fractions and decimals to solve word problems, operate with negative integers, and solve multi-step word problems involving proportions with whole numbers. Students can solve simple algebraic problems including evaluating expressions, solving simultaneous linear equations, and using a formula to determine the value of a variable. Students can find areas and volumes of simple geometric shapes and use knowledge of geometric properties to solve problems. They can solve probability problems and interpret data in a variety of graphs and tables.

Grade 8 Intermediate Benchmark

Students can apply basic mathematical knowledge in straightforward situations. They can add, subtract, or multiply to solve one-step word problems involving whole numbers and decimals. They can identify representations of common fractions and relative sizes of fractions. They understand simple algebraic relationships and solve linear equations with one variable. They demonstrate understanding of properties of triangles and basic geometric concepts including symmetry and rotation. They recognize basic notions of probability. They can read and interpret graphs, tables, maps, and scales.

Grade 8 Low Benchmark

Students have some basic mathematical knowledge. The few items at this level provide some evidence that students can do basic computations with whole numbers without a calculator. They can select the two-place decimal closest to a whole number. They can multiply two-place decimal numbers by three-place decimal numbers with calculators available. They recognize some basic terminology and read information from a line on a graph.

Grade 4 Advanced Benchmark

Students can apply their understanding and knowledge in a wide variety of relatively complex situations. They demonstrate a developing understanding of fractions and decimals and the relationship between them. They can select appropriate information to solve multi-step word problems involving proportions. They can formulate or select a rule for a relationship. They show understanding of area and can use measurement concepts to solve a variety of problems. They show some understanding of rotation. They can organize, interpret, and represent data to solve problems.

Grade 4 High Benchmark

Student can apply their knowledge and understanding to solve problems. Student can solve multistep word problems involving addition, multiplication, and division. They can use their understanding of place value and simple fractions to solve problems. They can identify a number sentence that represents situations. Students show understanding of three-dimensional objects, how shapes can make other shapes, and simple transformation in a plane. They demonstrate a variety of measurement skills and can interpret and use data in tables and graphs to solve problems.

Grade 4 Intermediate Benchmark

Students can apply basic mathematical knowledge in straightforward situations. They can read, interpret, and use different representations of numbers. They can perform operations with three and four-digit numbers and decimals. They can extend simple patterns. They are familiar with a range of two-dimensional shapes and read and interpret different representations of the same data.

Grade 4 Low Benchmark

Students have some basic mathematical knowledge. Students demonstrate an understanding of whole numbers and can do simple computations with them. They demonstrate familiarity with the basic properties of triangles and rectangles. They can read information from simple bar graphs.

from http://timss.bc.edu/PDF/t03_download/T03_M_Chap2.pdf

2003 Performance

In 2003, the international averages were:

Benchmark	Grade 4	Grade 8
advanced	9%	7%
high	33%	23%
intermediate	63%	49%
low	82%	74%

There is quite a wide variation around these means. For example, Singapore is head and shoulders above everyone, scoring 44% advanced, 77% high, 93% intermediate, 99% low at grade 8, and 38% advanced, 73% high, 91% intermediate, 97% low at grade 4. The only countries that come close are also Asian: Chinese Taipei, Hong Kong, Japan, and the Republic of Korea (for Grade 8; grade 4 figures weren't available). The highest of the remaining countries at grade 8 was Hungary at 11% advanced, 41% high, 75% intermediate, 95% low, and at grade 4 England at 14% advanced, 43% high, 75% intermediate, 93% low -- a substantial difference in results! But still a vast improvement over those at the bottom of the table. Here's 2 tables roughly grouping countries, using the top performing country in each group as a benchmark:

Grade 8	advanced	high	intermediate	low
highest performing countries (Singapore)	44%	77%	93%	99%
Singapore, Chinese Taipei, Republic of Korea, Hong Kong, Japan
above average countries (Hungary)	11%	41%	75%	95%
Hungary, Netherlands, Belgium, Estonia, Slovak Republic, Australia, United States
slightly below average countries (Malaysia)	6%	30%	66%	93%
Malaysia, Russian Federation, Israel, Latvia, Lithuania, England, New Zealand, Scotland
below average countries (Romania)	4%	21%	52%	79%
Romania, Serbia, Sweden, Slovenia, Italy, Bulgaria, Armenia
really below average countries (Cyprus)	1%	13%	45%	77%
Cyprus, Moldova, Macedonia, Jordan, Indonesia, Egypt, Norway, Lebanon, Palestinian National Authority, Iran, Chile, Philippines, Bahrain, South Africa, Tunisia, Morocco, Botswana, Saudi Arabia, Ghana

note that the range at the bottom end is still very large; although most of the countries in the last category at least got over 50% to the low benchmark, 8 did not -- the worst only got 9% through.

Grade 4	advanced	high	intermediate	low
highest performing countries (Singapore)	38%	73%	91%	97%
Singapore, Hong Kong, Japan, Chinese Taipei
above average countries (England)	14%	43%	75%	93%
England, Russian Federation, Belgium, Latvia, Lithuania, Hungary
slightly below average countries (Cyprus)	6%	30%	66%	93%
Cyprus, United States, Moldova, Italy, Netherlands, Australia, New Zealand
below average countries (Scotland)	4%	21%	52%	79%
Scotland, Slovenia, Armenia, Norway
really below average countries (Philippines)	1%	13%	45%	77%
Philippines, Iran, Tunisia, Morocco

note that there are substantially fewer countries' results available at grade 4

You can find out more about international comparisons of achievements in mathematics, science and reading at the official website for TIMSS (Trends in International Mathematics and Science Study) & PIRLS (Progress in International Reading Literacy Study): http://timss.bc.edu/

The full 2003 Mathematics Report can be downloaded at: http://timss.bc.edu/timss2003i/mathD.html

Science

Grade 8 Advanced Benchmark

Students demonstrate a grasp of some complex and abstract science concepts. They can apply knowledge of the solar system and of Earth features, processes, and conditions, and apply understanding of the complexity of living organisms and how they relate to their environment.

They show understanding of electricity, thermal expansion, and sound, as well as the structure of matter and physical and chemical properties and changes. They show understanding of environmental and resource issues. Students understand some fundamentals of scientific investigation and can apply basic physical principles to solve some quantitative problems. They can provide written explanations to communicate scientific knowledge.

Grade 8 High Benchmark

Students demonstrate conceptual understanding of some science cycles, systems, and principles. They have some understanding of Earth’s processes and the solar system, biological systems, populations, reproduction and heredity, and structure and function of organisms. They show some understanding of physical and chemical changes, and the structure of matter. They solve some basic physics problems related to light, heat, electricity, and magnetism, and they demonstrate basic knowledge of major environmental issues. They demonstrate some scientific inquiry skills. They can combine information to draw conclusions; interpret information in diagrams, graphs and tables to solve problems; and provide short explanations conveying scientific knowledge and cause/effect relationships.

Grade 8 Intermediate Benchmark

Students can recognize and communicate basic scientific knowledge across a range of topics. They recognize some characteristics of the solar system, water cycle, animals, and human health. They are acquainted with some aspects of energy, force and motion, light reflection, and sound. Students demonstrate elementary knowledge of human impact on and changes in the environment. They can apply and briefly communicate knowledge, extract tabular information, extrapolate from data presented in a simple linear graph, and interpret pictorial diagrams.

Grade 8 Low Benchmark

Students recognize some basic facts from the life and physical sciences. They have some knowledge of the human body and heredity, and demonstrate familiarity with some everyday physical phenomena. Students can interpret some pictorial diagrams and apply knowledge of simple physical concepts to practical situations.

Grade 4 Advanced Benchmark

Students can apply knowledge and understanding in beginning scientific inquiry. Students demonstrate some understanding of Earth’s features and processes and the solar system. They can communicate their understanding of structure, function, and life processes in organisms and classify organisms according to major physical and behavioral features. They demonstrate some understanding of physical phenomena and properties of common materials. Students demonstrate beginning scientific inquiry knowledge and skills.

Grade 4 High Benchmark

Students can apply knowledge and understanding to explain everyday phenomena. Students demonstrate some knowledge of Earth structure and processes and the solar system and some understanding of plant structure, life processes, and human biology. They demonstrate some knowledge of physical states, common physical phenomena, and chemical changes. They provide brief descriptions and explanations of some everyday phenomena and compare, contrast, and draw conclusions.

Grade 4 Intermediate Benchmark

Students can apply basic knowledge and understanding to practical situations in the sciences. Students demonstrate knowledge of some basic facts about Earth’s features and processes and the solar system. They recognize some basic information about human biology and health and show some understanding of development and life cycles of organisms. They know some basic facts about familiar physical phenomena, states, and changes. They apply factual knowledge to practical situations, interpret pictorial diagrams, and combine information to draw conclusions.

Grade 4 Low Benchmark

Students have some elementary knowledge of the earth, life, and physical sciences. Students recognize simple facts presented in everyday language and context about Earth’s physical features, the seasons, the solar system, human biology, and the development and characteristics of animals and plants. They recognize facts about a range of familiar physical phenomena — rainbows, magnets, electricity, boiling, floating, and dissolving. They interpret labeled pictures and simple pictorial diagrams and provide short written responses to questions requiring factual information.

from http://timss.bc.edu/PDF/t03_download/T03_S_Chap2.pdf

2003 Performance

In 2003, the international averages were:

Benchmark	Grade 4	Grade 8
advanced	7%	6%
high	30%	25%
intermediate	63%	54%
low	82%	78%

There is, again, wide variation around these means. Singapore is again head and shoulders above everyone. The only countries that come close are also Asian: Chinese Taipei, Hong Kong, Japan, and the Republic of Korea (for Grade 8; grade 4 figures weren't available). The highest of the remaining countries at grade 8 was Hungary at 11% advanced, 41% high, 75% intermediate, 95% low, and at grade 4 England at 14% advanced, 43% high, 75% intermediate, 93% low — a substantial difference in results! But still a vast improvement over those at the bottom of the table. Here's 2 tables roughly grouping countries, using the top performing country in each group as a benchmark:

Grade 8	advanced	high	intermediate	low
highest performing countries (Singapore)	33%	66%	85%	95%
Singapore, Chinese Taipei
above average countries (Republic of Korea)	17%	57%	88%	98%
Republic of Korea, Japan, Hungary, England, Hong Kong, Estonia
slightly above average countries (United States)	11%	41%	75%	93%
United States, Australia, Sweden, New Zealand, Slovak Republic, Netherlands, Lithuania, Slovenia, Russian Federation, Scotland
slightly below average countries (Israel)	5%	24%	57%	85%
Israel, Latvia, Malaysia, Italy, Bulgaria, Romania, Belgium, Jordan, Norway
below average countries (Serbia)	2%	16%	48%	79%
Serbia, Macedonia, Moldova, Armenia, Palestinian National Authority, Egypt, Iran
really below average countries (Chile)	1%	5%	24%	56%
Chile, South Africa, Cyprus, Bahrain, Indonesia, Lebanon, Philippines, Saudi Arabia, Morocco, Tunisia, Botswana, Ghana

again the range at the bottom end is still very large; although many of the countries in the last category at least got over 50% to the low benchmark, 7 did not -- the worst only got 13% through.

Grade 4	advanced	high	intermediate	low
highest performing countries (Singapore)	25%	61%	86%	95%
Singapore, England, Chinese Taipei, United States, Japan
above average countries (Russian Federation)	11%	39%	74%	93%
Russian Federation, Hungary, Australia, New Zealand, Italy, Latvia, Hong Kong
slightly below average countries (Scotland)	5%	27%	66%	90%
Scotland, Moldova, Netherlands, Lithuania, Slovenia, Belgium
really below average countries (Cyprus)	2%	17%	55%	86%
Cyprus, Norway, Armenia
really below average countries (Philippines)	2%	6%	19%	34%
Philippines, Iran, Tunisia, Morocco

note that there are substantially fewer countries' results available at grade 4

You can find out more about international comparisons of achievements in mathematics, science and reading at the official website for TIMSS (Trends in International Mathematics and Science Study) & PIRLS (Progress in International Reading Literacy Study): http://timss.bc.edu/

The full 2003 Science Report can be downloaded at: http://timss.bc.edu/timss2003i/scienceD.html

PIRLS

PIRLS is an international study of reading literacy involving 35 countries. It began in 2001, and is intended to take place every five years. It assesses performance at year 4 (around 10 years of age), although in a few cases the students are in their 3rd or 5th year of formal schooling. The PIRLS 2001 assessment was based on eight different texts of 400 to 700 words in length – four literary and four informational. Test items were designed to measure four major processes of reading comprehension:

• Focus on and Retrieve Explicitly Stated Information.
  The student needed to recognize the relevance of the information or ideas presented in the text in relation to the information sought, but looking for specific information or ideas typically involved locating a sentence or phrase (approximately 20% of the assessment).
• Make Straightforward Inferences.
  Based mostly on information contained in the texts, usually these types of questions required students to connect two ideas presented in adjacent sentences and fill in a “gap” in meaning. Skilled readers often make these kinds of inferences automatically, recognizing the relationship even though it is not stated in the text (approximately 40%).
• Interpret and Integrate Ideas and Information.
  For these questions, students needed to process the text beyond the phrase or sentence level. Sometimes they were asked to make connections that were not only implicit, but needed to draw on their own knowledge and experiences (approximately 25%).
• Examine and Evaluate Content, Language, and Textual Elements.
  These questions required students to draw on their knowledge of text genre and structure, as well as their understanding of language conventions and devices (approximately 15%).

23 of the 35 countries had average reading scores significantly above the international average of 500; the range was large, with the highest scoring country (Sweden) scoring 561, compared to the lowest scoring 327 (Belize). I've grouped them into five categories according to performance. As with the TIMSS results, the highest performing country in the group is the one whose average score is given:

	average	range1
highest performing countries (Sweden)	561
Sweden, Netherlands, England, Bulgaria, Latvia, Canada, Lithuania, Hungary, United States, Italy, Germany, Czech Republic		542-561
above average countries (New Zealand)	529
New Zealand, Scotland, Singapore, Russian Federation, Hong Kong, France, Greece		524-529
average countries (Slovak Republic)	518
Slovak Republic, Iceland, Romania, Israel, Slovenia, Norway		499-518
below average countries (Cyprus)	494
Cyprus, Moldova, Turkey, Macedonia		442-494
really below average countries (Colombia)	422
Colombia, Argentina, Iran, Kuwait, Morocco, Belize		327-422

1. the difference between the country with the lowest average and the one with the highest average

It should be noted that the range of difference between the highest 5% and lowest 5% of students in most countries was 200 to 300 points -- similar to the range in average performance across countries.

In all countries, girls had significantly higher achievement than boys. Italy had the smallest difference, with an 8-point difference compared an 11-point or greater difference for all other countries. The international average was 20 points. Countries with a difference of 25 points or more included Moldova, New Zealand, Iran, Belize and Kuwait.

For more details on countries' performance, see http://timss.bc.edu/pirls2001i/pdf/P1_IR_Ch01.pdf

Although the PIRLS, like the TIMSS, used benchmarks, the performance on the benchmarks as a whole for each country doesn't seem to be available. However, you can read about benchmark items and countries' achievements on particular ones at http://timss.bc.edu/pirls2001i/pdf/P1_IR_Ch03.pdf

The full 2001 Literacy Report can be downloaded at: http://timss.bc.edu/pirls2001i/PIRLS2001_Pubs_IR.html

This is the last part in my series on understanding scientific text. In this part, as promised, I am going to talk about the difficulties novices have with scientific texts; what they or their teachers can do about it; and the problems with introductory textbooks.

The big problem for novices is of course that their lack of knowledge doesn’t allow them to make the inferences they need to repair the coherence gaps typically found in such texts. This obviously makes it difficult to construct an adequate situation model. Remember, too, that to achieve integration of two bits of information, you need to have both bits active in working memory at the same time. This, clearly, is more difficult for those for whom all the information is unfamiliar (remember what I said about long-term working memory last month).

But it’s not only a matter a matter of having knowledge of the topic itself. A good reader can compensate for their lack of relevant topic knowledge using their knowledge about the structure of the text genre. For this, the reader needs not only to have knowledge of the various kinds of expository structures, but also of the cues in the text that indicate what type of structure it is. (see my article on Reading scientific text for more on this).

One of the most effective ways of bringing different bits of information together is through the asking of appropriate questions. Searching a text in order to answer questions, for example, is an effective means of improving learning. Answering questions is also an effective means of improving comprehension monitoring (remember that one of the big problems with reading scientific texts is that students tend to be poor at judging how well they have understood what was said).

One of the reasons why children typically have pronounced deficits in their comprehension monitoring skills when dealing with expository texts, is that they have little awareness that expository texts require different explanations than narrative texts. However, these are trainable skills. One study, for example, found that children aged 10-12 could be successfully taught to use “memory questions” and “thinking questions” while studying expository texts (Elshout-Mohr & van Daalen-Kapteijns, 2002).

Moreover, the 1994 study found that when the students were trained to ask questions intended to access prior knowledge/experience and promote connections between the lesson and that knowledge, as well as questions designed to promote connections among the ideas in the lesson, their learning and understanding was better than if they were trained only in questions aimed at promoting connections between the lesson ideas only (or if they weren’t trained in asking questions at all!). In other words, making explicit connections to existing knowledge is really important! You shouldn’t just be content to consider a topic in isolation; it needs to be fitted into your existing framework.

College students, too, demonstrate limited comprehension monitoring, with little of their self-questioning going deeply into the material. So it may be helpful to note Baker’s 7 comprehension aspects that require monitoring:

1. Your understanding of the individual words
2. Your understanding of the syntax of groups of words
3. External consistency — how well the information in the text agrees with the knowledge you already have
4. Internal consistency — how well the information in the text agrees with the other information in the text
5. Propositional cohesiveness — making the connections between adjacent propositions
6. Structural cohesiveness —integrating all the propositions pertaining to the main theme
7. Information completeness — how clear and complete the information in the text is

Think of this as a checklist, for analyzing your (or your students’) understanding of the text.

But questions are not always the answer. The problem for undergraduates is that although introductory texts are presumably designed for novices, the students often have to deal not only with unfamiliar content, but also an approach that is unfamiliar. Such a situation may not be the best context for effective familiar strategies such as self-explanation.

It may be that self-explanation is best for texts that in the middle-range for the reader — neither having too little relevant knowledge, or too much.

Introductory texts also are likely to provide only partial explanations of concepts, a problem made worse by the fact that the novice student is unlikely to realize the extent of the incompleteness. Introductory texts also suffer from diffuse goals, an uneasy mix of establishing a basic grounding for more advanced study, and providing the material necessary to pass immediate exams.

A study of scientific text processing by university students in a natural situation found that the students didn’t show any deep processing, but rather two kinds of shallow processing, produced by either using their (limited knowledge of) expository structures, or by representing the information in the text more precisely.

So should beginning students be told to study texts more deeply? The researchers of this study didn’t think so. Because introductory texts suffer from these problems I’ve mentioned, in particular that of incomplete explanations, they don’t lend themselves to deep processing. The researchers suggest that what introductory texts are good for is in providing the extensive practice needed for building up knowledge of expository structures (and hopefully some necessary background knowledge of the topic! Especially technical language).

To that end, they suggest students should be advised to perform a variety of activities on the text that will help them develop their awareness of the balance between schema and textbase, with the aim of developing a large repertory of general and domain-specific schemata. Such activities / strategies include taking notes, rereading, using advance organizers, and generating study questions. This will all help with their later construction of good mental models, which are so crucial for proper understanding.

There are many memory strategies that can be effective in improving your recall of text. However, recent research shows that it is simplistic to think that you can improve your remembering by applying any of these strategies to any text. Different strategies are effective with different types of text.

One basic classification of text structure would distinguish between narrative text and expository text. We are all familiar with narrative text (story-telling), and are skilled in using this type of structure. Perhaps for this reason, narrative text tends to be much easier for us to understand and remember. Most study texts, however, are expository texts.

Unfortunately, many students (perhaps most) tend to be blind to the more subtle distinctions between different types of expository structure, and tend to treat all expository text as a list of facts. Building an effective mental model of the text (and thus improving your understanding and recall) is easier, however, if you understand the type of structure you're dealing with, and what strategy is best suited to deal with it.

Identifying structure

Five common types of structure used in scientific texts are:

• Generalization: the extension or clarification of main ideas through explanations or examples
• Enumeration: listing of facts
• Sequence: a connecting series of events or steps
• Classification: grouping items into classes
• Comparison / contrast: examining the relationships between two or more things

Let's look at these in a little more detail.

Generalization

In generalization, a paragraph always has a main idea. Other sentences in the paragraph either clarify the main idea by giving examples or illustrations, or extend the main idea by explaining it in more detail. Here's an example:

Enumeration

Enumeration passages may be a bulleted or numbered list, or a list of items in paragraph form, for example:

Sequence

A sequence describes a series of steps in a process. For example:

Classification

In classification, items are grouped into categories. For example:

Comparison / contrast

This type of text looks at relationships between items. In comparison, both similarities and differences are studied. In contrast, only the differences are noted. For example:

[examples taken from Cook & Mayer 1988]

A study [1] involving undergraduate students inexperienced in reading science texts (although skilled readers otherwise) found that even a small amount of training substantially improved the students' ability to classify the type of structure and use it appropriately.

Let's look briefly at the training procedures used:

Training for generalization

This involved the following steps:

• identify the main idea
• list and define the key words
• restate the main idea in your own words
• look for evidence to support the main idea
  • what kind of support is there for the main idea?
  • are there examples, illustrations?
  • do they extend or clarify the main idea?

Training for enumeration

This involved the following steps:

• name the topic
• identify the subtopics
• organize and list the details within each subtopic, in your own words

Training for sequence

This involved the following steps:

• identify the topic
• name each step and outline the details within each
• briefly discuss what's different from one step to another

[Only these three structures were covered in training]

Most effective text structures

Obviously, the type of structure is constrained by the material covered. We can, however, make the general statement that text that encourages the student to make connections is most helpful in terms of both understanding and memory.

In light of this, compare/contrast would seem to be the most helpful type of text. Another text structure that is clearly of a similar type has also been found to be particularly effective: refutational text. In a refutational text, a common misconception is directly addressed (and refuted). Obviously, this is only effective when there is a common misconception that stands in the way of the reader's understanding -- but it's surprising how often this is the case! Incompatible knowledge is at least as bad as a lack of knowledge in hindering the learning of new information, and it really does need to be directly addressed.

Refutational text is however, not usually enough on its own. While helpful, it is more effective if combined with other, supportive, strategies. One such strategy is elaborative interrogation, which involves (basically) the student asking herself why such a fact is true.

Unfortunately, however, text structures that encourage connection building are not the most common type of structure in scientific texts. Indeed, it has been argued that "the presentation of information in science textbooks is more likely to resemble that of a series of facts [and thus] presents an additional challenge that may thwart readers' efforts to organize text ideas relative to each other".

Most effective strategies

The fundamental rule (that memory and understanding are facilitated by any making of connections) also points to the strategies that are most effective.

As a general rule, strategies that involve elaborating the connections between concepts in a text are the most effective, but it is also true that the specifics of such strategies vary according to the text structure (and other variables, such as the level of difficulty).

Let's look at how such a linking strategy might be expressed in the context of our five structures.

Generalization

Restatement in your own words -- paraphrasing -- is a useful strategy not simply because it requires you to actively engage with the material, but also because it encourages you to connect the information to be learned with the information you already have in your head. We can, however, take this further in the last stage, when we look for the evidence supporting the main idea, if we don't simply restrict ourselves to the material before us, but actively search our minds for our own supporting evidence.

Enumeration

This text structure is probably the hardest to engage with. You may be able to find a connective thread running through the listed items, or be able to group the listed items in some manner, but this structure is the one most likely to require mnemonic assistance (see verbal mnemonics and list-learning mnemonics).

Sequence

With this text structure, items are listed, but there is a connecting thread — a very powerful one. Causal connections are ones we are particularly disposed to pay attention to and remember; they are the backbone of narrative text. So, sequence has a strong factor going for it.

Illustrations particularly lend themselves to this type of structure, and research has shown that memory and comprehension is greatly helped when pictures portraying a series of steps, in a cause-and-effect chain, are closely integrated with explanatory text. The closeness is vital — a study that used computerized instruction found dramatic improvement in memory when the narration was synchronous with the animation, for example, but there was no improvement when the narration was presented either before or after the text. If you are presented with an illustration that is provided with companion text, but is not closely integrated with it, you will probably find it helpful to integrate it with the text yourself.

Classification

Classification is frequently as simple as grouping items. However, while this is in itself a useful strategy that helps memory, it will be more effective if the connections between and within groups are strong and clear. Connections within groups generally emphasize similarities, while connections between groups emphasize both similarities (between closely connected groups) and differences. Ordering groups in a hierarchical system is probably the type of arrangement most familiar to students, but don't restrict yourself to it. Remember, the important thing is that the arrangement has meaning for you, and that the connections emphasize the similarities and differences.

Compare / contrast

This type of structure lends itself, of course, to making connections. Your main strategy is probably therefore to simply organize the material in such a way as to make those connections clear and explicit.

In the last part I talked about retrieval structures and their role in understanding what you’re reading. As promised, this month I’m going to focus on understanding scientific text in particular, and how it differs from narrative text.

First of all, a reminder about situation models. A situation, or mental, model is a retrieval structure you construct from a text, integrating the information in the text with your existing knowledge. Your understanding of a text depends on its coherence; it’s generally agreed that for a text to be coherent it must be possible for a single situation model to be constructed from it (which is not to say a text that is coherent is necessarily coherent for you —that will depend on whether or not you can construct a single mental model from it).

There are important differences in the situation models constructed for narrative and expository text. A situation model for a narrative is likely to refer to the characters in it and their emotional states, the setting, the action and sequence of events. A situation model for a scientific text, on the other hand, is likely to concentrate on the components of a system and their relationships, the events and processes that occur during the working of the system, and the uses of the system.

Moreover, scientific discourse is rooted in an understanding of cause-and-effect that differs from our everyday understanding. Our everyday understanding, which is reflected in narrative text, sees cause-and-effect in terms of goal structures. This is indeed the root of our superstitious behavior — we (not necessarily consciously) attribute purposefulness to almost everything! But this approach is something we have to learn not to apply to scientific problems (and it requires a lot of learning!).

This is worth emphasizing: science texts assume a different way of explaining events from the way we are accustomed to use — a way that must be learned.

In general, then, narrative text (and ‘ordinary’ thinking) is associated with goal structures, and scientific text with logical structures. However, it’s not quite as clear-cut a distinction as all that. While the physical sciences certainly focus on logical structure, both the biological sciences and technology often use goal structures to frame their discussions. Nevertheless, as a generalization we may say that logical thinking informs experts in these areas, while goal structures are what novices focus on.

This is consistent with another intriguing finding. In a comparison of two types of text —ones discussing human technology, and ones discussing forces of nature — it was found that technological texts were more easily processed and remembered. Indications were that different situation models were constructed — a goal-oriented representation for the technological text, and a causal chain representation for the force of nature text. The evidence also suggested that people found it much easier to make inferences (whether about agents or objects) when human agents were involved. Having objects as the grammatical subject was clearly more difficult to process.

Construction of the situation model is thus not solely determined by comprehension difficulty (which was the same for both types of text), but is also affected by genre and surface characteristics of the text.

There are several reasons why goal-oriented, human-focused discourse might be more easily processed (understood; remembered) than texts describing inanimate objects linked in a cause-effect chain, and they come down to the degree of similarity to narrative. As a rule of thumb, we may say that to the degree that scientific text resembles a story, the more easily it will be processed.

Whether that is solely a function of familiarity, or reflects something deeper, is still a matter of debate.

Inference making is crucial to comprehension and the construction of a situation, because a text never explains every single word and detail, every logical or causal connection. In the same way that narrative and expository text have different situation models, they also involve a different pattern of inference making. For example, narratives involve a lot of predictive inferences; expository texts typically involve a lot of backward inferences. The number of inferences required may also vary.

One study found that readers made nine times as many inferences in stories as they did in expository texts. This may be because there are more inferences required in narratives — narratives involve the richly complex world of human beings, as opposed to some rigidly specified aspect of it, described according to a strict protocol. But it may also reflect the fact that readers don’t make all (or indeed, anywhere near) the inferences needed in expository text. And indeed, the evidence indicates that students are poor at noticing coherence gaps (which require inferences).

In particular, readers frequently don’t notice that something they’re reading is inconsistent with something they already believe. Moreover, because of the limitations of working memory, only some of the text can be evaluated for coherence at one time (clearly, the greater the expertise in the topic, the more information that can be evaluated at one time — see the previous newsletter’s discussion of long-term working memory). Less skilled (and younger) readers in particular have trouble noticing inconsistencies within the text if they’re not very close to each other.

Let’s return for a moment to this idea of coherence gaps. Such gaps, it’s been theorized, stimulate readers to seek out the necessary connections and inferences. But clearly there’s a particular level that is effective for readers, if they often miss them. This relates to a counter-intuitive finding — that it’s not necessarily always good for the reader if the text is highly coherent. It appears that when the student has high knowledge, and when the task involves deep comprehension, then low coherence is actually better. It seems likely that knowledgeable students reading a highly coherent text will have an “illusion of competence” that keeps them from processing the text properly. This implies that there will be an optimal level of coherence gaps in a text, and this will vary depending on the skills and knowledge base of the reader.

Moreover, the comprehension strategy generally used with simple narratives focuses on referential and causal coherence, but lengthy scientific texts are likely to demand more elaborate strategies. Such strategies are often a problem for novices because they require more knowledge than can be contained in their working memory. Making notes (perhaps in the form of a concept map) while reading can help with this.

Next month I’ll continue this discussion, with more about the difficulties novices have with scientific texts and what they or their teachers can do about it, and the problems with introductory textbooks. In the meantime, the take-home message from this is:

Understanding scientific text is a skill that must be learned;

Scientific text is easier to understand the more closely it resembles narrative text, with a focus on goals and human agents;

How well the text is understood depends on the amount and extent of the coherence gaps in the text relative to the skills and domain knowledge of the reader.