C D Hulshof
email: c.d.hulshof@utwente.nl

T De Jong

Using just-in-time information to support discovery learning about geometrical optics in a computer-based simulation

Using just-in-time information to support scientific discovery learning about geometrical optics in a computer-based simulation

Casper Hulshof, Ton de Jong

Introduction

While computers continue to advance into virtually all aspects of our culture, their effective use in education is still surrounded by controversy [START_REF] Stoll | High Tech Heretic. Why Computers Don't Belong in the Classroom and Other Reflections by a Computer Contrarian[END_REF]. Although considerable progress has been made in understanding of the opportunities and potential that computers offer for educational practice, some aspects remain problematic. A review by [START_REF] Angrist | New evidence on classroom computers and pupil learning[END_REF] of the Israeli Tomorrow-98 programme, a billion-dollar venture aimed at creating an environment supportive of integrating information technologies in the classroom, has shown very little beneficial short-term effects of increased computer use. This has led the authors to conclude that 'money spent on CAI [Computer Aided Instruction] in Israel would have been better spent on other inputs (p. 761)'. These findings show that, viewed on a large scale, there exist many factors that impede successful implementation of computers in educational situations. On a smaller scale, much research has been devoted to studying the specific circumstances under which computers can be effective learning tools. This is usually done by comparing various types of computer-based instruction to more traditional forms of learning. One type of instruction that fully exploits the potential of computer-regulated learning is known as discovery learning [START_REF] De | Scientific discovery learning with computer simulations of conceptual domains[END_REF]. Discovery learning means that the content of a domain is not explicitly stated to learners. Instead, learners have to 'discover' the material for themselves using techniques that can be compared to the behavior of a scientist who explores a domain. A technique that has proven useful in eliciting discovery learning processes is by the use of computer simulations [START_REF] De | Learning and instruction with computer simulations[END_REF][START_REF] De | Scientific discovery learning with computer simulations of conceptual domains[END_REF]. A computer simulation provides students with a virtual environment in which they can design and perform different types of experiments, and observe the effect of manipulating variables in various ways. When used as an instructional tool, students' task is to induce the relations between variables in the simulated domain through exploration, experimenting, and discovery. A central characteristic of discovery learning is that information is not delivered to students in a piecemeal fashion. Instead, the process is a relatively demanding one: students are required to gather evidence themselves and accordingly construct, shape, and modify personal hypotheses. It is supposed that during learning, through various 'acts of discovery', experimental evidence is transformed in such a way that new information can be induced [START_REF] Bruner | The act of discovery[END_REF]. The complete process of experimenting and inducing rules should gradually lead to understanding of the model that underlies behavior of the simulated system. In an information-processing description of the discovery learning process, two main cognitive processes can be distinguished: transformative and regulative processes [START_REF] Njoo | Exploratory learning with a computer simulation for control theory: Learning processes and instructional support[END_REF]. Transformative processes include all the reasoning and decision making that guide manipulating a computer simulation and extracting information from it. These involve orientation, hypothesis generation, hypothesis testing, and drawing conclusions. The goal of transformative processes is to produce new information. Regulative processes are meant to control the discovery learning process on a metacognitive level. This involves monitoring one's own behavior, keeping track of progress, and planning in advance what steps to undertake.

Since discovery learning involves so many different processes that need to occur simultaneously on different levels of cognition, it is perhaps not surprising that it has been difficult to prove its effectiveness. The problems that students encounter in discovery learning can be classified into four components: hypothesis generation, design of experiments, interpretation of data, and regulation of learning [START_REF] De | Scientific discovery learning with computer simulations of conceptual domains[END_REF]. Proper performance of all the component tasks that make up the learning process requires both (partial) knowledge, and skills necessary to execute and complete each task. Research on discovery learning has identified at least four factors that influence the learning process, and determine its effectiveness: prior domain-specific knowledge, generic knowledge of quantitative and qualitative relations between variables, discovery skill, and metacognition (De Jong, Beishuizen, Hulshof, Prins, van Rijn, van Someren, Veenman & Wilhelm, in press). Domain-specific knowledge and generic (domain-general) knowledge are partially independent entities. Discovery skill refers to a specfic ability, ie. student's aptitude for performing and interpreting experiments. Metacognition refers to the generic ability to regulate discovery learning processes. Knowledge and skills contribute differently to the process of transformation and regulation. Here, a short description is given of the way knowledge and skill influence discovery learning.

Knowledge plays an important role in determining the steps that learners undertake in the process of experimenting with a simulation and discovering information. Even transformative processes that yield knowledge themselves require at least some prior knowledge to function. For example, lack of prior domain-specific knowledge makes the process of orientation difficult, since learners who lack knowledge will have trouble separating relevant from irrelevant variables, which will cause them to overlook potentially interesting relations between variables [START_REF] Veermans | Intelligent support for discovery learning: Using opportunistic learner modeling and heuristics to support simulation based discovery learning[END_REF]. The determining role that prior knowledge plays in setting up a context for discovery learning is reflected in the SDDS framework (Scientific Discovery as Dual-space Search) by [START_REF] Klahr | Dual space search during scientific reasoning[END_REF]. Klahr & Dunbar likened the process of discovery of a rule (that is, discovery of the relation between an input and output variable) to problem solving. SDDS extends the problem solving model by [START_REF] Newell | Human Problem Solving[END_REF], which describes it as a search through a problem space. In SDDS, two ('dual') search spaces are postulated: hypothesis space and experiment space. In this view, the process of discovery entails traversing both search spaces, so that the end result is a set of rules that correctly describe the observed behavior of variables. During learning, searching each of the problem spaces requires different decisions. [START_REF] Van Joolingen | An extended dual search space model of scientific discovery learning[END_REF] have given an overview of the decisions that guide the search through the two spaces. For example, in experiment space search is guided by the choice of variables to manipulate and the values to assign to these. In hypothesis space, search is guided by manipulations that operate on one of more of the set of hypotheses a learner has in mind (e.g., change a hypothesis about a qualitative relation between two variables into a quantitative). When behavior during rule discovery is studied, a a broad distinction can be observed between students who follow a hypothesis-oriented approach and students who follow an experimentoriented approach. Students can be broadly classified as being either 'theorists' or 'experimenters', based on the manner in which they discover a rule. Klahr has stated that the distinction between an experimenter and theorist approach to rule discovery stems from differences in prior knowledge (Klahr, 2000, p. 77). From this description it becomes clear that knowledge not only should help students in making sense of a learning situation, but should also influence the discovery learning process itself. Although the claim that prior knowledge affects rule discovery to a large extent is supported by empirical data, it is uncertain if this notion can be extrapolated to include discovery learning in the type of complex learning environment that a computer simulation entails. In previous studies that we conducted [START_REF] Hulshof | Discovery of ideas and ideas about discovery: The influence of prior knowledge on scientific discovery learning in computer-based simulations[END_REF][START_REF] Hulshof | Prior knowledge and scientific discovery learning[END_REF], only limited effects of prior knowledge on discovery learning were found. Moreover, it was found that prior domainspecific knowledge about the simulated domain (geometrical optics) was poor in general. Learning results showed that students did not improve from pretest to posttest, and even tended to get worse. The implication of these findings is that discovery learning with a computer simulation can be severely hampered by students' lack of prior knowledge.

In addition to knowledge, students' level of discovery skills is assumed to influence the type of experiments a student performs in a simulation, especially the sequence in which experiments are performed. For discovery learning to be successful, experiments should be performed in such a way that enough cognitive resources needed to make inferences from observation of the experiment data are available. However, many students show shortcomings in their approach to experimenting. As [START_REF] Tschirgi | Sensible reasoning: A hypothesis about hypotheses[END_REF] has observed, students tend to change more than one variable from experiment to experiment, which in most cases is a suboptimal strategy. In a study by [START_REF] Klahr | The equivalence of learning paths in early science instruction: effects of direct instruction and discovery learning[END_REF], the effect of direct instruction on learning about the 'control of variables strategy' (CVS; also known as the VOTAT-strategy, cf. [START_REF] Tschirgi | Sensible reasoning: A hypothesis about hypotheses[END_REF] was compared with that of discovery learning about the strategy. The results were in favor of direct instruction: not only did more children in the 'direct instruction' condition learn about the strategy, they also were better able to make better scientific judgements. As Klahr and Nibam point out, the main difference between direct instruction and discovery learning in their experiment lay in the information and feedback that was given to students: whereas students in the direct instruction condition received ample feedback and information, students in the discovery learning condition were shown no examples or given any explanations.

Given the findings that many students appear to lack the knowledge and skills that are required for successful discovery learning, the implication seems to be clear: discovery learning can not be as effective as direct instruction because many students lack either or both the knowledge or the skills necessary to guide transformative and regulative learning processes. However, there are a number of ways in which the situation can be remedied.

Students can be supported during discovery learning in various ways. Regulative processes can be supported by structuring a computer simulation, for example by starting with a simple simulation and gradually moving on to more complex situations. Transformative processes (Orientation, hypothesis generation and testing, and drawing conclusions) can be fostered by adding 'support tools' to a computer simulation. However, support is not always effective. It can even have the effect of degrading, or hampering, performance [START_REF] Pieters | When support hampers: Constructivism and minimalism in supporting knowledge acquisition[END_REF]. For example, Van Joolingen (1993) used a structured hypothesis scratchpad to help students in making hypotheses explicit. It was expected that students who had this scratchpad at their disposal would come up with more and better hypotheses than students who did not. The actual result was that students who had the hypothesis scratchpad available conducted fewer experiments and stated fewer hypotheses than students who did not. Addition of a hypothesis scratchpad to a computer simulation did not help students in conducting experiments and generating hypotheses. The problem may have been that the addition of a tool to an already complex learning situation provided an extra task to learners, which they found difficult to cope with given the relatively short time for the experiment. [START_REF] Shute | A comparison of learning environments: All that glitters…[END_REF] has argued that tools that aim at supporting discovery learning can interfere with the learning process itself. This interference disrupts compilation of knowledge and can have an adverse effect on learning. Although support tools may help in the process of hypothesis testing, they do not provide the information that is needed for orientation. [START_REF] Shute | A comparison of learning environments: All that glitters…[END_REF] found that the availability of an on-line hypertext containing definitions and explanations had a positive effect on discovery learning. [START_REF] Leutner | Guided discovery learning with computer-based simulation games: effects of adaptive and non-adaptive instructional support[END_REF] emphasizes that providing information to students should be carefully timed, since providing it before a learning session does not seem to help students in making sense of a learning situation. [START_REF] Berry | Explanation and verbalization in a computerassisted search task[END_REF] argue that the effect of providing information is much higher if it is made available to students as soon as they need it, on a 'just-in-time'-base. A potential problem in offering support in the form of tools or on-line information is that it may influence the discovery learning process. This may detract from the potential advantages that this type of learning has over direct instruction. Therefore, to preserve the characteristics of discover learning, support should have minimal influences on the learning process itself. Students should be free to explore a simulation environment, and to design their own experiments.

Based on the discussion above, it was hypothesized that an effective type of support for discovery learning, which does not disrupt the learning process, should conform to the following three principles: support should be 1) unobtrusive, 2) minimal, and 3) available on a just-in-time base. The support should be unobtrusive in the sense that it should not be necessary for all students to use the support as part of the learning process. The optimal situation is one in which students should be able to get by with a minimum access to the support measure. Support should be minimal because otherwise it will interfere with the learning process, which may have detrimental effects. Also, support is meant to scaffold the discovery learning of students, not replace it. Finally, support should be available at the moment that students require it. This means that support should not be provided too early (in which case students may be confused by it) or too late (in which case the support has lost its relevancy).

The question that the present research attempts to answer is twofold. First, is it possible to provide the type of just-in-time support to students in the context of discovery learning with a computer simulation? Secondly, is such support effective, compared to a situation in which it is not available? To answer these questions, a special type of 'knowledge tips' support was created. This support consisted of a number of short blocks of text that contained domainspecific and general information. An attempts was made to deliver these information blocks in such a way so that they were available to students on a just-in-time base. The support was made to be unobtrusive in the sense that students were not required to access the information at any time during learning. The information blocks were minimal in the sense that the information that was given was short and succinct. The context in which the support measure was evaluated was a computer simulation (called 'Optics') on the topic of geometrical optics. The simulation was set up in such a way that there was a lot of room for exploration of the relations underlying the behavior of light through a lens.

It is expected that access to knowledge tips fosters discovery learning with the Optics simulation. Students who can access knowledge tips during learning should show a higher learning gain than students who work freely with a computer simulation. Further, it is expected that if the support measure succeeds in being unobtrusive, it should not interfere too much with the learning process itself. Therefore, only minimal differences between students who use knowledge tips and students who do not are expected with respect to interaction behavior with a computer simulation. Finally, it is expected that there will be variation in the number of tips that students access. Students with poor domain-specific prior knowledge are expected to make less use of knowledge tips than students with high domain-specific knowledge. This expectation is in accordance with a finding by [START_REF] Hasselerharm | The relation between instructional control strategies and performance and attitudes in computer-based in-struction[END_REF], who found that students with little prior domain-specific knowledge made less use of an optional support tool than students with high ability.

Method

Participants

Thirty-two subjects participated in the experiment. All subjects were students who were following technical vocational education, The mean age of the subjects was 19 years. Subjects came from two school classes, both in the same year of study. All had followed a physics course as part of the curriculum. Subjects received a financial compensation of €23 for their participation in both experimental sessions.

Design

A two-group pre-posttest design was used for the experiment. Two conditions were used, an experiment condition and a control condition. Subjects were randomly assigned to one condition. Computers were positioned in such a way that subjects in different conditions were not seated next to each other. In both conditions, subjects worked with the Optics simulation environment. In the experiment condition, subjects were informed about the ability to access so-called 'knowledge tips'. In the control condition, subjects did not have access to these tips.

Learning environment

The learning environment that was used in the experiment was the Optics computer simulation (De Jong et al., in press). The simulated domain was basic geometrical optics. The simulation allowed subjects to experiment with a virtual optical workbench, in which the properties of light and different kinds of lenses could be explored. In Figure 1, an example of the simulation is shown.

- -------------------------- ---------------------------The figure shows a complex, but not untypical, situation that subject could create. The simulation can be divided into two areas. At the top, a row of icons indicates the operations subjects could select to perform in the simulation. The bottom part, called the 'working area', is where subjects could manipulate objects, such as different types of lamps and lenses. In the figure, a large lamp on the left is sending light in all directions. Light passes through a surface filled with holes. Together, the holes form an L-shape. Divergent light rays that originate from the holes in the surface pass through a lens (marked 'C'). Because the surface is within the focal length of the lens, no image is projected on the screen at the right. Instead, a virtual image is formed. This virtual image can be made visible by the use of the 'eye'-tool (positioned at the right). The virtual image is marked by a blue circle. It was possible to measure properties of the virtual image, as if it were a normal projected image. In the figure, the top row shows on the left three different lenses that were available to experiment with (the lenses had different focal distances). Next to the large lamp (which is positioned on the left of the working area, and can not be moved), a lamp with one light beam, a lamp with three divergent light beams, and a lamp with three parallel light beams were available. Both horizontal and vertical distances could be measured, and also the angle with which a light beam entered or exited the lens. Light beams could also be rotated a specific number of degrees. As an extra aid, light beams could be extended in any direction by adding one or more help lines. Subjects were allowed to make notes while they worked with the simulation. For this they were handed paper; there was no need to enter notes in the simulation itself.

Knowledge tips

In the experiment condition, nine knowledge tips were available to subjects. Figure 2 shows two examples of tips that were used in the experiment.

- -------------------------- ---------------------------As can be seen from the table, tips could consist of multiple parts. The first part of each tip contained domain-specific information on some concept of geometrical optics. The second part contained general advice on how experiments could be used in the Optics simulation to observe the information given in the first part. Also, relevant objects that could be used to perform appropriate experiments were listed. Finally, some tips gave a clue about the expected outcome of experiments. Knowledge tips could be accessed at any time by subjects, but they were not required to access any. In the experiment condition, the bottom line of the Optics simulation contained a set of nine small icons, one for each tip. Clicking on an icon would open a small popup-window in the simulation. Tips were not accessible immediately. Instead, new tips were made available every three minutes. The first tip was available after three minutes, the second after six, and so on until the last tip. After 27 minutes, all nine tips were available. When a tip became available, its corresponding icon changed color; it could then be accessed. Once a tip had become available, it could be accessed and closed as many times as subjects preferred.

Tests

Three pretests were administered: a test for domain-specific knowledge about geometrical optics, a test for generic knowledge about mathematical relations, and a test for experimentation skills in the context of a discovery task. At the end of the experiment, a domain-specific knowledge posttest was administered.

Two example items from the generic knowledge test about mathematical relations are shown in Figure 3. The test was a paper-and-pencil test, consisting of 32 items in total. Of these, 29 were multiple-choice items. The other items required a short written explanation, such as a formula.

- -------------------------- ---------------------------The test for domain-specific knowledge about geometrical optics was a paper-and-pencil multiple-choice test consisting of 30 items in total. Two example items are shown in Figure 4. The test contained items that asked for conceptual knowledge about geometrical optics, and items that required subjects to predict how changes in a situation would affect light propagation through a lens. In the test, pictures that represented situations similar to those in the Optics simulation were used to present situations about which multiple questions were asked.

- -------------------------- ---------------------------The test for discovery skills used a combination of a computer task and a paper-and-pencil test. The computer task was an adapted version of the FILE task (described in detail in [START_REF] Hulshof | FILE: A Tool for the Study of Inquiry Learning[END_REF]; also see Wilhelm, Beishuizen & van Rijn, 2004). The maximum time subjects were allowed to work with the computer task was 30 minutes. After subjects had indicated that they knew the effect of the five variables in the FILE task, a paper-and-pencil test was administered, which consisted of 6 short questions. Test items required subjects to state the effect of each of the five variables in the FILE task on the outcome. Based on the answers, subjects were classified in one of 4 different levels. Subjects were classified as level 1 if they did not find correct main effects, and no interaction effect; as level 2 if they did find correct main effects but no interaction effect; as level 3 if they found correct main effects and the correct interaction effect, but also one or more incorrect effects; finally, as level 4 if they found correct main effects and the correct interaction effect, and no other effects. The category a subject is classified in can be used as a measure for the level of discovery skills, with level 1 being the lowest, and level 4 the highest level of discovery skills. While answering the test, subjects were allowed to examine the experiments they had carried out and any notes they had made on paper, but they were not allowed to create any new experiments in FILE.

Process measures

All operations that subjects performed in the Optics computer simulation were automatically registered by the computer they were working on. This made it possible to analyze the activity subjects showed while they worked with the simulation.

Procedure

The experiment was divided over two sessions, about one week after another. The sessions lasted about 80 minutes. In both conditions the same procedure was followed. In the first session the pretests were administered. The tests were administered one by one in the following sequence: first the generic knowledge test, which took about 25 minutes to complete, next the domain-specific knowledge test which took about 15 minutes, and finally the discovery skills test. To log in on the computer for the discovery skills FILE task, each subject was given a login code. Subjects worked on the FILE task for about 30 minutes, after which a short paper-and-pencil test was administered. The second session was spent on working with the Optics computer simulation. Subjects were informed at the start of the session that they would receive a knowledge test afterwards. All subjects were given an instruction sheet which contained an explanation of buttons and tools in the Optics computer simulation. This sheet remained available to subjects during the session. Both conditions received similar instructions. However, subjects in the experiment condition received added instruction on the use of knowledge tips. In both conditions, subjects were given the assignment to perform experiments with Optics, and to use the tools they had at their disposal in the virtual environment of the simulation. The instruction encouraged subjects to make use of the clues that were given by the simulation, and to make notes on paper. During the session, subjects who got stuck were always referred to the assignment and the instruction sheet. No further instructions were given. All subjects started experimenting with the Optics simulation at the same time. Subjects worked with the simulation for approximately 50 minutes, after which the program was ended and the domain-specific knowledge posttest was handed out. The posttest was administered the same way as the pretest, and took subjects approximately 15 minutes to complete.

Results

Two types of results are relevant for the present experiment: performance on the three pretests and the posttest, and the process data. Analysis showed no difference between the two school classes that participated in the experiment, so only results for the complete group are described in this section. Test results are described first, followed by process results.

Test measures

Reliability for the test for generic knowledge of mathematical relations (as measured by Cronbach's α) was 0.71. Test scores ranged from 11 to 28 (out of 32 test items), with a mean score of 21.1 (standard deviation 4.2).

Reliability for the domain-specific knowledge pretest was 0.51, and for the posttest 0.66. The mean pretest score was 15.3 out of 30 test items (standard deviation 3.7), mean posttest score was 14.9 (standard deviation 4.2). Test scores ranged for the pretest from 9 to 25, and for the posttest from 4 to 21. Overall, no difference between pretest and posttest scores was found. Figure 5 shows in a graph the test results split for the experiment and control condition.

- ---------------------------Figure 5 about here ----------------------------As can be seen from the graph, there is a curious result: subjects in the control condition performed relatively well on the pretest. However, for this condition performance on the posttest was lower than on the pretest. In contrast, in the experiment condition mean performance increased. A one-tailed t-test of independent samples shows that the difference between improvement from pretest to posttest in the two conditions is statistically significant; (F 1,24 =3.21; p<.05).

Dependent on the results of the test for discovery skills, subjects were classified into one of four different levels. Of the 32 subjects, 8 were classified on level 1 (the lowest level), 17 as level 2, 3 as level 3, and 4 as level 4 (the highest level). One implication of this result is that 78 Percent of the subject group was not able to discover an interaction effect in data from the FILE task.

In Table 1, correlations between the four knowledge measures are shown (generic knowledge, domain-specfic prior and posttest knowledge, and discovery skills). As can be seen, all between-test correlations are close to zero. In addition, for both conditions in the experiment correlations between pretest and posttest domain-specific knowledge test scores were computed. For the control condition, the result shows a correlation of 0.52, a moderately high pretest-posttest correlation. For the experiment condition, the correlation is -0.47, moderately negative. These results replicate earlier findings [START_REF] Hulshof | Prior knowledge and scientific discovery learning[END_REF].

Process measures

In the session in which subjects worked with the Optics simulation, 27 subjects participated, 15 in the control condition and 12 in the experiment condition. In the experiment condition, one subject did not access any tips at all. Because the reason for this is unclear (which makes it difficult to assign the results to any of the two conditions), it was decided to discard the process results for this subject from the analysis. All operations subjects performed in the simulation were registered and available for further analysis. For the present study, two results are especially relevant: differences between the experimental conditions with regard to interaction with Optics, and the use of knowledge tips by subjects in the experiment condition.

Interaction with Optics. The analysis of interaction with Optics focused on a subset of all possible operations: the 'basic operations'. Basic operations are those that are central to the process of experimentation. Together, the basic operations constitute more than three quarters of all operations that subjects performed in the simulation. Three different operations were examined: addition of objects to the working area in the simulation, removal of objects from the working area, and movement of objects in the working area. On average, subjects in the control condition performed 70.3 (SD=43.4), and in the experiment condition 60.1 basic operations (SD=37.5). This difference is not statistically significant. In Figure 6, a comparison between the experimental conditions is shown for each of the basic operations.

- -------------------------- ---------------------------As can be seen from the figure, there are small but consistent differences between subjects in the two conditions for all three basic operations. Subjects in the control condition performed more basic operations than subjects in the experiment condition. This finding can be explained by the availability of knowledge tips in the experiment condition: the fact that accessing and reading knowledge tips takes time influenced subjects' level of activity.

Because most subjects in both conditions scored close to the mean on the different knowledge tests, a comparison of subjects with low or high knowledge or skill could only be carried out on a small number of cases. Only subjects who scored more than one standard deviation below or above the mean were included in the analysis. For generic knowledge, this meant that two groups were formed of subjects who scored below 17 (n=4) or above 25 (n=4). The results are shown in Figure 7.

----------------------------Figure 7 about here ----------------------------As can be seen in the figure, subjects with high generic knowledge were more active in working with the Optics simulation than subjects with poor generic knowledge. For domainspecific knowledge, the groups were formed of subjects who scored below 12 (n=6) or above 19 (n=5). Results are shown in Figure 8.

----------------------------Figure 8 about here ----------------------------The results are similar to the findings for generic knowledge: subjects with more knowledge about optics showed more activity for all basic operations. For discovery skills, the groups were formed of subjects who were classified at the lowest level (n=6) or at the highest level (n=3). Results are shown in Figure 9.

----------------------------Figure 9 about here ----------------------------

The results differ from the other comparisons. Both groups performed a similar amount of Add and Delete operations, but subjects with high discovery skills performed much more Move operations than subjects with low discovery skills.

Use of tips. In the experiment condition, subjects could access knowledge tips if they wished to do so. The minimum number of tips that was viewed was 1, the maximum all 9 tips. The average number of accessed tips was 6 (standard deviation 2.6). Table 2 shows correlations between performance on the different test measures and the number of tips accessed by subjects.

- --------------------------- ----------------------------As can be seen from the table, there is a statistically significant correlation between domainspecific prior knowledge and the number of tips accessed in the simulation: more competent subjects accessed more knowledge tips than others. Although not statistically significant, it can be observed that there is also a positive relation between the level of generic knowledge and the number of accessed tips.

Discussion

This study examined the effect of facilitating access to domain-specific and generic information during scientific discovery learning with a computer simulation called 'Optics'. The study compared the interaction behavior with Optics and knowledge acquisition of two randomly created groups of students: one group who worked with Optics without support (the control condition), and one group who were supported while they worked with Optics (the experiment condition). The type of support used in the experiment condition was the use of a small set of 'knowledge tips', hints containing general information on the topic of the simulation: geometrical optics. A distinguishing feature of these tips is that they were not used to guide students while they explored and experimented with the discovery learning environment. Instead, students could decide for themselves whether or not they wanted to make use of the available tips. Information was available to students on a 'just in time'-base, which means that it could be voluntarily accessed during learning. As a result of the relatively small difference between the conditions that were used in the experiment, the interaction behavior with Optics was similar for subjects in both the control and the experiment condition. Subjects in the control condition were only a little more active than subjects in the experiment condition. The differences can be explained by the time taken by subjects in the experiment condition to access and read the knowledge tips. Differences between the two conditions become more apparent when the results from the domain-specific knowledge tests are compared. Subjects in the experiment condition showed a significant learning gain from pretest to posttest, in contrast to subjects in the control condition who even showed a small decline in knowledge. This finding suggests that subjects in the experiment condition benefited from the availability of tips. It should be pointed out that the questions that were used to test for domain knowledge did not ask for information that was contained within the knowledge tips. Who benefits most? In the control condition, a positive correlation was found between performance on the pretest and posttest. In the experiment condition, a negative correlation was found. The positive correlation in the control condition indicates that the effect of working with Optics was similar for all subjects in this condition. Further analysis shows that the negative correlation in the experiment condition can be explained by the performance of a number of subjects who did poorly on the pretest but showed a large increase from pretest to posttest. It can be concluded that the subjects who benefited most from the availability of tips were those subjects who showed a low understanding of the domain prior to the experiment. It is interesting to note that the positive correlation between the number of tips that subjects accessed during the experiment and domain-specific prior knowledge indicates that subjects with low prior knowledge accessed fewer knowledge tips than subjects with higher prior knowledge. This means that in some cases, accessing only a few knowledge tips resulted in a large increase in performance on the posttest.

The other tests that were administered in the experiment show mixed results. Most subjects performed well on generic knowledge measures, which means that they had no trouble in understanding the type of qualitative and quantitave relations that occur between variables in the Optics simulation. The relatively high level of generic knowledge may have facilitated understanding of the knowledge tips in the experiment condition. In contrast to the good results on the generic knowledge test, on the test for discovery skills most subjects showed a relatively poor performance. Classification of subjects was based on the number and type of rules they were able to discover after working with the FILE task. This showed that 78% of the subjects did not mention the presence of an interaction effect. Given the fact that the FILE task was relatively simple because its experiment space is relatively small, the learning gain in the experiment condition after working with the complex Optics simulation is almost a surprising outcome. Optics should probably not be viewed as just a complex version of the FILE discovery task, since FILE deals with an artificial topic and Optics deals with geometrical optics, a real-world topic. This may explain the absence of a relation between performance on the discovery skills test and knowledge gain from working with Optics.

What this study shows is that computer simulations can be effective tools for learning, even when the process of discovery learning is applied to the complex domain of geometrical optics. The unobtrusive method of just-in-time support helps to improve the effectiveness of discovery learning.

Tables and Figures

  Figure 1 about here ----------------------------

  Figure 2 about here ----------------------------

  Figure 3 about here ----------------------------

  Figure 4 about here ----------------------------

  Figure 6 about here ----------------------------

Figure 1 .

 1 Figure 1. Example interface of the Optics simulation environment. Explanation given in text

Figure 2 .Figure 5 .Figure 6 .

 256 Figure 2. Two example tips (tip 1 and 6), used in the experiment condition

Figure 8 .Figure 9 .

 89 Figure 8. Comparison on basic operations for low and high domain-specific knowledge

Table 2 about here

 2

Table 1 .

 1 Correlations between prior knowledge test measures

	Knowledge measure Domain posttest	Generic Discovery skills
	Domain pretest	.13	.27	.13
	Domain posttest		.04	.05
	Generic			.25

Table 2 .

 2 Correlations between knowledge measures and the number of accessed tips

	Knowledge measure	Accessed tips
	Generic knowledge	.39
	Discovery skills	-.24
	Domain-specific prior knowledge	.66 *
	Domain-specific post knowledge	-.36

Acknowledgements

Development of the Optics simulation took place in the context of the Inductive Learning project, which was supported by a grant from the Dutch National Science Foundation (NWO 575-22.002). Optics was programmed by Jan Wielemaker (Department of Social Science Informatics, University of Amsterdam, the Netherlands) to whom the authors would like to express their gratitude. The authors would also like to thank Pascal Wilhelm, Frans Prins, Hedderik van Rijn, Marcel Veenman, Wouter van Joolingen, Maarten van Someren, Bert Bredeweg and Bob Wielinga for their useful comments.


Hans Van Der Meij
email: meij@edte.utwente.nl

E-mail was embedded in a project in design & technology education in elementary school. During four lessons children worked in groups on building a flying object. These groups communicated through e-mail with groups of children from another school. The analyses of the e-mails, as viewed from distributed cognition theory, focus on the exchange patterns and content.

Two characteristic exchange patterns are stacking and compounding. In stacking e-mails are sent out quickly enough to afford a 'just-in-time' exchange of information. In compounding the e-mails transcend lessons. An 'old' section of the e-mail reacts to the partner's e-mail about a previous lesson. A 'new' section deals with the current lesson.

Question-answer exchanges accounted for only about 15% of the communications. Connected discourse with explicit or implicit references to the partner's e-mail was likewise scarce. Groups mainly connected to each other through adoption, leading to shared scenarios of "We tell you our story -You tell us yours".

The conclusion discusses the impact of the task on the children's communication. Among others, a precise definition and teaming of the task is deemed necessary to favour embedded e-mail use. Because the genre of e-mail use in elementary school is yet to be defined the authors caution against imposing many constraints on what children write to each other.

Introduction

Mountaineers sometimes say that they climb mountains "because they are there". A similar statement appears to be true for computers in school. Teachers sometimes use computers in school because they are there. Just as in mountaineering, success in school does not come easily; there are many obstacles to overcome. Interestingly, most of these obstacles have little to do with the technology itself. [START_REF] Salomon | What does the design of effective CSCL require and how do we study its effects[END_REF], among others, indicates that the success or failure of using computers in school largely depends on the orchestration of the various actors and factors in the whole learning environment.

We report here about a project on e-mail use by children from the upper grades of elementary school. The project employed e-mail as a tool to communicate about the lesson topic rather than as an issue in itself; e-mail was used as a means rather than an end. The main reason for employing e-mail as a tool in a real problem solving task directly relates to our conviction that such an approach improves domain-related learning and also affords better personalisations of the tool by the children. This conviction is in line with constructivist approaches to education.

The larger part of the preparations for the project involved creating a series of four lessons and lesson materials in which e-mail use formed an integrated, domain-related activity of the children. Developed in close collaboration with teachers, the lessons evolved around the problem of creating a flying object. Each lesson contained a prescribed e-mail moment. A teacher manual that supported the participants, detailed each lesson and suggested topics for the e-mail exchanges.

A critical element in the lesson plans involved teamwork because collaborative learning was deemed to be especially relevant for the relatively complex problem that the children were asked to solve (see [START_REF] Cohen | Restructuring the classroom: Conditions for productive small groups[END_REF][START_REF] Dysthe | The multivoiced classroom Written[END_REF][START_REF] Mercer | Children's talk and the development of reasoning in the classroom[END_REF]. The children were teamed up in small groups. During the various phases of problem solving these teams were to communicate about the project as a group, as part of the whole classroom, and as a conversational partner of a group of children from another school who worked on the same project. To facilitate the latter aspect, the teacher manual contained information about setting up an e-mail project with another school.

The results from the project were examined with two notions from distributed cognition theory in mind, namely the idea that information & cognition is distributed and that learning objectives are (partly) defined by the learner (e.g., [START_REF] Cole | A cultural-historical approach to distributed cognition in Salomon G (ed) Distributed cognitions[END_REF][START_REF] Dysthe | The multivoiced classroom Written[END_REF][START_REF] Mason | Sharing cognition to construct scientific knowledge in school context: The role of oral and written discourse Instructional[END_REF][START_REF] Pea | Practices of distributed intelligence and designs for education in Salomon G (ed) Distributed cognitions. Psychological and educational considerations[END_REF].

The use of e-mail entails a distribution of information & cognition in which time and space play a prominent role. E-mail affords an a-synchronous communication, meaning that there is always a time-lag between sending a message and receiving a reaction. This time-lag inevitably affects the uses of the tool. On the positive side it may stimulate reflection as children have more time to think through their responses. On the negative side it may reduce the chances of realising a truly connective discourse (versus "knowledge telling", see [START_REF] Scardamalia | Technologies for knowledge-building discourse[END_REF] and getting a timely response to pressing questions. E-mail use also affords communicating groups to bridge their distribution in space. In schools the factors that affect the success of such an enterprise include: (a) the proper (e.g., synchronous) scheduling of the lessons and their e-mail moments in the teamed-up classrooms, (b) creating a common ground for communication (e.g., by groups introducing themselves), and (c) the choice of an appropriate means of responding to an e-mail (e.g., by annotating, repeating or paraphrasing a portion of the received e-mail). Some of these issues are discussed when we present the results from analysing the content of the children's e-mails. In addition, we detail the exchange patterns that emerged. These patterns illustrate how the e-mails actually were distributed during the project. E-mail is a lean medium. It is not much more than white space on a computer screen on which a message can be written. Apart from dictating a predominantly verbal form of communication, e-mail does not impose much structure on what gets communicated. In other words, e-mail gives children a great deal of freedom to personalise their communications. But there is no total freedom. The task is an important structuring factor and children are expected to communicate mainly about their design task. In addition, the teacher manual contained some suggestions for structuring the e-mails. Even so, it are the groups who determine how and what they communicate by and large. In other words, the objectives for the use of e-mail are defined by the children and the results thereof are illustrated with the findings of the analyses of the content of their communications.

Method

Participants

Sixteen elementary schools in the Netherlands participated in the project and data were gathered from 301 children with a mean age of 11 years. The children formed 87 groups that sent out a total of 214 e-mails. In preparing for the project, special attention was given to three top-5 obstacles to computer use in Dutch schools, namely: (a) lack of sufficient (and fast) computers, (b) insufficient knowledge and training support, and (c) lack of lesson materials containing an integrated computer component (Ten [START_REF] Brummelhuis | ICT-Monitor 1998-1999 basisonderwijs OCTO[END_REF]. The obstacle of computer access was handled by asking the participating schools to guarantee easy pupil access to the computer(s). The problem of technical know-how was circumvented by accepting only schools in which the participating teacher was a skilled e-mail user and by offering technical support upon request. The introduction already described how we handled the third obstacle.

Coding and scoring

An important aspect of the distributed nature of e-mail use transpires in the exchange patterns that emerge. These patterns are operationally defined as a mixture of the score for the exchange rate and participation rate for a group. The exchange rate measures the mean frequency of e-mails sent out by a group in a particular lesson. A rate of more than one e-mail is considered to be reasonably fast paced. The participation rate measures the continuity of the exchanges over the lesson series. A score of 75% indicates that a group has e-mailed its partner three out of the four lessons. Such a score also reflects a high level of participation.

Combining the low and high scores for exchange rate and participation rate yields four distinct exchange patterns. Figure 1 presents the criteria for these scores. Each distinct pattern is also given an appropriate name. For example, the exchange pattern of a group is characterized as incidental when the group sends out no more than one e-mail in a particular lesson and has e-mailed only during one or two of the four lessons. Chance alone favours the presence of the incidental and structural exchange pattern because of the interdependence of the exchange rate and participation rate.

- -------------------------------------INSERT FIGURE 1 HERE --------------------------------------Figure 1: The exchange patterns that emerge from combining the scores for continuity in sending out e-mails in the four lessons (participation rate) with the scores for frequency of e-mails sent within lessons (exchange rate)

Coding of the content of e-mails followed a two-step procedure with segmentation preceding categorization. In segmentation, each e-mail is divided into meaningful units such as a principle sentence or a (subordinate) clause. Adding all the segments in an e-mail gives an impression of the mean volume of an e-mail.

In categorization, each segment is classified on four dimensions: (1) linguistic expression, (2) topic, (3) motivation and (4) connectivity. These dimensions and their subcategories were derived bottom-up as well as from theory. With regard to the later, only a few useful ideas could be abstracted from studies on e-mail exchanges (e.g., [START_REF] Atkinson-Christie | Using e-mail within a classroom based feminine pedagogy[END_REF][START_REF] Duin | Collaboration via e-mail and internet relay chat: Understanding time and technology[END_REF][START_REF] Mckeon | The nature of children's e-mails in one classroom[END_REF][START_REF] Williams | On-line communication patterns of novice internet users Computers in the[END_REF]. Our main source of inspiration was the work of [START_REF] Mercer | The quality of talk in children's collaborative activity in the classroom Learning and Instruction[END_REF] on analysing face to face communications between children. A codebook was created to support the categorization by independent observers. Interobserver agreements yielded a satisfactory score of 0.66 (Cohen kappa) and higher for these codes.

Figure 2 illustrates the coding of two segments from an e-mail. Note that the Topic dimension is the only dimension in which the main categories are not mutually exclusive. Only here some segments can belong to two categories instead of just one. For example, the segment "We have a tip for you concerning the design of your aircraft" scores into the category Communication and in Domain Talk.

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------------------------------------- INSERT FIGURE 2 HERE --------------------------------------

Figure 2: An illustration of a segmented and categorized e-mail

In scoring, the mean results for all groups were first calculated for individual lessons. These scores were later combined to create an overall picture of the content of the e-mails sent during the whole project. The tables that are presented in the next section now portray the 'average' e-mail for the average lesson.

Results & Discussion

Exchange patterns

The incidental pattern dominated. On a total of 87 recorded e-mail groups, 56 groups (64.4%) had more or less haphazard exchanges. The exchanges of yet another 17 groups followed a structural pattern. In this pattern the e-mails are relatively plentiful. An impressive 94% of these groups came from schools in which the children already regularly used e-mail before participating in the project.

The exchanges of 11 groups (12.6%) fitted perfectly within a compound pattern. In this pattern each e-mail ideally consists of an 'old' section, in which the group reacts to a previous e-mail, and a 'new' section that provides the stimulus for its e-mail partner (see Figure 3).

- -------------------------------------INSERT FIGURE 3 HERE ------------------------------------- In a stacking pattern groups interact more than once between lessons. Information is now given and received 'just-in-time' because the children react quickly to the issues brought up by the e-mail partner. The exchanges of 3 groups (3.4%) fitted this pattern (see Figure 4).

- --------------------------------------INSERT FIGURE 4 HERE ---------------------------------------Figure 4: In stacking, e-mails are exchanged swiftly enough for groups to share views on current issues (i.e., the same lesson)

There was a statistically significant correlation between participation rate and exchange rate on the one hand, and e-mail volume on the other (respectively τ = 0.40, p < 0.001, and τ = 0.69, p < 0.001). Partial correlations with the effect of participation rate filtered out still showed a positive and statistically significant relationship between exchange rate and volume (τ xy.z = 0.56, p < 0.001). In other words, groups who sent out more e-mails also tended to make these e-mails longer. Perhaps this signals that e-mail functionality carries its own rewards.

The reasoning could be like this: longer e-mails → are likely to carry more substance → which make the interaction more valuable → which help keep up participation.

The content of the e-mails Dimension 1. Linguistic expression. The analyses in this dimension concentrated on three basic types of linguistic means: Statements, Questions and Responses. Statements are operationally defined as expressions that, unlike Questions, do not explicitly invite a reaction and that are also not clearly a reaction to a Question or a Statement from the partner. Reactions to a Question or Statement are classified as Responses. 1 shows that the e-mails consisted mainly of Statements. Almost 9 of the 11 segments in the average email are Statements. The presence of Questions and Responses is about balanced and seems to suggest that groups discuss their partner's question(s) in their response. A detailed inspection of the data shows otherwise, however. Only 59% of the Questions led to a Response. The remainder of the Responses were reactions to a Statement.

In speculating about the meaning of this finding some intriguing ideas can be advanced: (1) the reaction-inviting nature of questions (the 'illocuting force') is not as strong as people sometimes expect, (2) just as in face to face communications, it is not always necessary to ask a question to evoke a reaction, (3) it may not be wise to constrain the use of e-mail to an exchange of questions and answers. The latter idea addresses the rather widespread conception among lay people that e-mail is optimally suited for a swift exchange of questions and answers. The data indicate that this would have cut-off 85% of the communications if teachers would have allowed only for this type of exchange, all other things being equal. Perhaps more importantly, it would have deprived the groups from engaging in valuable social talk. Such talk about personally relevant issues helps build a relationship with the partner and contributes to creating a common ground (see [START_REF] Anderson | Principles of communication and emotion in social interaction in Anderson P A and Guerrero L K[END_REF][START_REF] Baker | The role of grounding in collaborative learning tasks in Dillenbourg P (ed) Collaborative learning[END_REF].

Dimension 2. Topic. The topic dimension includes the categories of Communication, Social Talk and Domain Talk. Communication covers all segments in which the children say something about the process of communication. For example, a group may ask whether the other group has the ability to provide an answer to their question ("Do you know it?"), or it may express a desire to receive an answer ("We hope that you write back soon"). The category also contains expressions of an introductory nature such as "We have a question".

Social Talk includes 'chatter' about pop music, sports and the like. Within this category we also classified expressions about the children's preferences, knowledge and skills for school work (e.g., "I am good with computers").

Domain Talk covers all expressions about the domain of design & technology. If e-mail is to serve its role as an important means for reflection, articulation and evaluation about the task at hand, the main body of an e-mail should probably fall within this category. The subcategories here are: context, goal or objective, result or evaluation, materials & tools, planning and design principles. From lesson two onwards there was much less Social Talk; the proportion of Social Talk for lesson 2, 3 and 4 was respectively 26%, 23% and 32%. The proportion of Domain Talk increased rapidly after the first lesson and then remained stable and fairly high. For lesson 1, 2, 3 and 4 the scores were 17%, 46%, 53% and 44%. In short, these findings reveal that there is a good deal of social talk but that this talk does not dominate the children's emails. In most e-mails the children are writing about task related matters.

Almost a third of the expressions deal with Communication. This seems to be just about the right amount. As in writing a letter, the children should follow certain formal rules of conduct, or 'netiquette' as these are called in email jargon. Like in any other form of communication there should also be room for such talk in e-mail exchanges.

Dimension 3. Motivation. This dimension consists of the categories Evaluation and Problem & Trouble.

Evaluation refers to all expressions containing a judgement or assessment. Judgements may relate to a situation, a product, or a personal characteristic. For example, a group might write "our group is cozy", or label an event as "funny". Evaluations could also involve the flying object, as in "Our plane did not go very far". Examples of Evaluation as an assessment of personal qualities or capacities are expressions such as "I am pretty good in many things in school" and "I know a lot about computers". Table 3 shows that Evaluations are found in 19% of the average e-mail and Problem & Trouble in 11% of the cases. Apart from their apparent function as an outlet for certain emotions, both types of motivational expressions may be important for improving commitment. Expressed emotions such as feeling unsure or having a row, now become distributed and possibly shared. Thereby they may fortify the bond within and between groups.

Dimension 4. Connectivity. This dimension contains all expressions of interactivity or connected discourse. We distinguish three types: Connected Reactions, Unconnected Reactions, and Adoption. In a Connected Reaction the children explicitly refer to, or repeat, (part of) their partner's question or statement before reacting. A typical example is "The gas you asked about is called helium". E-mail programs have a reply feature to facilitate this type of connectivity, but none of the groups used this feature. All groups created their e-mails from scratch.

In an Unconnected Reaction groups respond to an expression without making this known explicitly. An example is the expression "The answer is four" which can be understood only within the context of an ongoing exchange.

For the coding by the researchers this meant that the context had to be (re)constructed by consulting the e-mail of the corresponding group. For the receiving group of children an Unconnected Reaction is likewise incomprehensible unless the children consult the original e-mail, or remember the statement or question that triggered the response.

Adoption is an important and unique subcategory. It refers to expressions that are connected to each other by type similarity. In Adoption a group or child imitates a particular style or typology from another group or child. Among others, Adoption is found in introductory e-mails when group members use the same format for presenting themselves (e.g., "I am … and my hobbies are …"). To our knowledge, this format was spontaneously adopted by the other children in a group after being introduced by one of them. Adoption occurs within groups as well as across groups. About one segment (9%) of the average e-mail connects directly or indirectly to the e-mail topic of the partner group. The paucity of this aspect of connected discourse is compensated for by the presence of Adoption.

Adoptions makes up 39% of the average e-mail. The score for Adoption varies considerable for the four lessons.

There is a preponderance in the first lesson with a 70% score, then a drop to 21% and 16% in the second and third lesson and an increase to 45% for the final lesson. When Adoption is used it typically leads to a series of emails that can be characterised as "We tell you our story -You tell us yours".

Conclusion

The important role of the task is stressed in several key notions from distributed cognition theory (e.g., [START_REF] Cole | A cultural-historical approach to distributed cognition in Salomon G (ed) Distributed cognitions[END_REF]. Not surprisingly then, the task played a key role in the project. As indicated in the introduction, we chose to have children use e-mail as a tool as opposed to training them in the skills acquisition for e-mail use as an end in itself. For some children and groups this clearly led to some tension between the need to learn to use and the need to use. Often this problem was solved by mixing skilled and non-skilled children in a group so that the more experienced children could support the less experienced ones during their turn to work with e-mail. In this fashion e-mail was used in the way in which we think children are most likely to benefit from the experience, namely by embedding its use in solving a real task.

Distributed cognition theory also points to a strong impact of the task on teamwork. Among others, the task gives groups and group members a shared goal and perspective. The presence of a structural exchange pattern and findings on the topic of the e-mails and e-mail connectivity suggest that some of our efforts to create a shared (e.g., connected) discourse were successful. But looking back we think that the definition of the task for teaming up groups from different schools was not precise enough. That is, the project departed from the simple notion that the goal of creating a flying object would yield a sufficiently shared interest for the exchanges. It worked because, say, a balloon building group could communicate about general issues of design with an airplane building group. It would have been better, however, if we had teamed up groups who set out to create the same flying object. Then issues such as problem definition, choice of materials, and construction problems are even more likely to be really shared between groups.

Task factors also emerged in the differences that existed between the findings for the average e-mail, and the emails sent out during a particular lesson. Both the broader picture of the first and the detailed view of the latter were affected by task features. For example, what some teachers feared did not happen. The children did not use e-mail predominantly to chat about Madonna, soaps or hobbies. E-mail was used predominantly for task and domain-related purposes. In a similar vein, we think that not reducing e-mail usage to an exchange of questions and answers has had a positive effect on the communications. The link between a specific lesson, and hence task, and what gets communicated, most clearly transpires in the findings on the topic dimension. Among others the to-be-expected spike for social talk in the first communication is illustrative.

In conclusion, e-mail in school is not yet the integrated communication tool that it is in business settings. There is yet much to be studied and understood. There is yet a long way to go. We see the project as a first step towards defining the genre of e-mail use in elementary school (see [START_REF] Baron | Letters by phone or speech by other means: the linguistics of e-mail Language & Communication[END_REF]. But, just as in mountaineering, with the right equipment, motivation and endurance there are good chances for success. (8) || This is what we did. (9) || We used wood, a dirt bag, staples, some rope and a small pebble (10) || We got the wood from a store with home improvement materials. (11) || First we placed the three pieces of wood in a triangle and then we glued these together. (12) || … || We hope it will fly. (17) || … Hi Airways and Stunt Flyers, Thank your for your message. It was nice to hear that so many of you are playing volleyball. We too find Donald Duck a nice magazine.

Participation rate

Our design: You have a bicycle pump and you place a cork on it with a coke bottle.

-Figure 3 :

 3 Figure 3: In compounding, an e-mail ideally consists of two parts. One part deals with the last email from the partner group. In this Reaction the group reacts to issues from an earlier lesson. The second part is what the group would like to tell about their current situation. This Stimulus presents topics from the current lesson

Figure 2 .

 2 Figure 2. An illustration of a segmented and categorized e-mail.

Table 1 :

 1 The mean appearance of a linguistic expression in an e-mail

	Mean	Standard deviation

Table 2

 2 Table2indicates that Social talk and Domain Talk are found in about even proportions in the average e-mail. Compared to the total mean of 11 segments per e-mail, each comes close to a 50%-score. Detailed examinations of the data revealed that the finding for Social Talk is inflated by a dominating presence in the first lesson. In this first e-mail groups introduced themselves, as one would expect. Because groups added very little other information, 74% of the segments in the first e-mail moment consisted of Social Talk.

	: The mean appearance of a topical expression in an e-mail
		Mean	Standard deviation
	Communication	3.43	2.54
	Social Talk	5.44	4.40
	Domain Talk	5.58	1.61

Table 3 :

 3 The mean appearance of a motivational expression in an e-mail

	Mean	Standard deviation

Table 4 :

 4 The mean appearance of connective discourse in an e-mail

	Mean	Standard deviation

  ||We think your airplane looks great. (2) ||… Today we succeeded completing our airplane.

			Low (25%-50%)	High (75%-100%)
		Low (0-1)	incidental	compounding
	Exchange rate
		High(>1)	stacking	structural
	Figure 1: The exchange patterns that emerge from combining the scores for continuity in
	sending out e-mails in the four lessons (participation rate) with the scores for frequency of
	e-mails sent within lessons (exchange rate)
	From:	j.vink@francis1.edith.antenna.nl
	...
	Subject:	Flying Flintstones to KLM'ers
	Hello KLM-ers, (1)

  Then you shoot the pump away. It was Gerjo's idea. According to Gerjo it will fly 50 meters. Yeah. Right. So, in a way it will be launched. … We hope that it will work and that the Flying Bottle will stay airborne for a long time. Perhaps you can use this. In compounding, an e-mail ideally consists of two parts. One part deals with the last e-mail from the partner group. In this Reaction the group reacts to issues from an earlier lesson. The second part is what the group would like to tell about their current situation. This Stimulus presents topics from the current lessonYet get from us an answer to the question. You can best use a plastic bag. Attach strings to it and then fix the bag to the basket that you inflate. We hope that it works.We have some questions for you too. We think our airplane might become too heavy. Do you think we should use other, lighter materials? And do you know where we might get these? Bye -bye the Daedalus In stacking, e-mails are exchanged swiftly enough for groups to share views on current issues (i.e., the same lesson)

	Hello Space Invaders,
	Reaction
	Stimulus
	Hi Daedalus,
	Bye Interfly Use We get it from John's father. Space Invaders Figure 3: Segment # 2 Reaction Stimulus expression -statement topic -design & technology motivation -evaluation connectivity -unconnected reaction Segment # 10 expression -statement topic -design & technology motivation -none connectivity -none Reaction Figure 4: