Tinkering or Sketching: Apprentices’ Use of … or Sketching: Apprentices’ Use of Tangibles and Drawings 169 search and the application of well-known procedures. Problem-solvers

P. Dillenbourg and M. Specht (Eds.): EC-TEL 2008, LNCS 5192, pp. 167–178, 2008. © Springer-Verlag Berlin Heidelberg 2008

Tinkering or Sketching: Apprentices’ Use of Tangibles and Drawings to Solve Design Problems

Patrick Jermann, Guillaume Zufferey, and Pierre Dillenbourg

CRAFT, Ecole Polytechnique Fédérale de Lausanne, station 1, 1015 Lausanne, Switzerland

{Patrick.Jermann,Guillaume.Zufferey,Pierre.Dillenbourg}@epfl.ch

Abstract. The articulation of practice and theory is a central problematic in a dual apprenticeship system that combines working in a company and attending courses at school. Design problems are proposed by teachers as a way to ad-dress theoretical concepts in a practical context. The difficulties encountered by apprentices while creating paper based sketches motivated the development of a tabletop warehouse simulation providing apprentices with a Tangible User In-terface in the form of a small-scale model. We compare drawings and tangible representational modalities with regards to three phases of design problem solv-ing. Tinkering with tangibles is described as an easy way to engage into the problem. The physical properties of tangibles facilitate the extraction of features relevant for verification. The limited expressiveness of tangibles allows appren-tices to focus on the search for a solution rather than on the representation of the problem space.

Keywords: Tangible Computing, Problem- and Project-based Learning, Prac-tice Fields, Initial Vocational Training, Field Studies.

1 Introduction

Vocational training in Switzerland concerns 70% of the 15 year old people after obligatory schooling. Training is organized to a large extend following a dual ap-proach: apprentices spend four days per week working in a company and attend courses in a professional school on the fifth day. Compared to a model that implies vocational schools only, the dual model presents the advantage that businesses finan-cially profit from the apprentices' work [1] and apprentices practice their trade in an authentic setting. Professional schools propose general courses (e.g. foreign languages or commercial law) as well as trade-specific courses. In addition, practical training for specialized aspects of the profession is provided by professional associations four weeks in a year.

A field study conducted at the beginning of this research in the field of logistics showed that the distribution of the apprenticeship over two different locations poses the problem of the articulation of practical and conceptual knowledge. Schools attempt to teach generalities: despite the efforts teachers invest in explaining and contextualiz-ing textbook examples, apprentices are not able (or willing) to transfer generalities into

168 P. Jermann, G. Zufferey, and P. Dillenbourg

their practice. From the teachers’ point of view, the central problem posed by school-ing with logisticians comes from their limited abstraction, reading and comprehension capabilities. It is for instance difficult for apprentices to imagine the effect of everyday practice on the behavior of a global logistics chain. It is also difficult for them to rea-son about numerical relationships, for example between storage surfaces and monetary flows or between the weight of a pallet and the maximum height a forklift is allowed to lift it. School is described by apprenticeship masters (who are responsible for the ap-prentices in companies) as something irrelevant for the apprentice’s daily practice. At the best, they recognize that conceptual knowledge might be useful in the later career of the apprentice. At the workplace, apprentices don't have the opportunity to apply the general skills they are taught in school. Especially in the beginning of the apprentice-ship, apprentices are mostly involved in the manual aspects of the profession (e.g. moving boxes, packaging goods). Organizational decisions (e.g. about the layout of a new warehouse), which would require the application of theories taught in school, are taken by the employees already in place. In addition, intellectual work is sometimes negatively perceived in predominantly manual professions (e.g. car mechanics, logis-tics, woodworker, etc.). In short, the dual system is missing a place where reflection on practice is encouraged and supported. There are however occasions where school ac-tivities aim at bridging the “abstraction gap” between practice and theory. The ware-house layout exercise which we describe in this paper precisely aims at embedding conceptual knowledge into an ill-defined design problem.

The differing nature of in- and out-of-school learning is well described by Res-nick’s Presidential Address to the American Educational Research Association [2]. Out of school learning (including at the workplace) is situated, distributed over people and tools whereas schooling is conceived as individual “mentation” on symbolic representations which (are supposed to) transfer to a wide array of situations. Unfor-tunately, transfer doesn’t happen, what is learned in schools is not useable in the workplace. The remedies proposed by situated learning ([3], [4]) to the problems faced by traditional schooling are well articulated in the ideas of practice fields [5] and authentic learning environments (see synthesis in [6]). These approaches advo-cate in favor of learning situations which are similar to the situations where knowl-edge will be used, feature ill-defined activities, provide access to expert performance, provide multiple roles and perspectives, support collaborative construction of knowl-edge, promote reflection and articulation. During the past two years we have worked in close relationship with two teachers from a professional school to design a tabletop small-scale simulation for logistics. The design was guided by the principles outlined by the practice fields approach. The general objective of our intervention is to enable teachers to propose problem-solving activities to the apprentices which are as close as possible to the real context of a warehouse.

2 Research Question

Design problems are ill-defined problems [7]: they have multiple solutions which are not contained in the description of the problem and which may be evaluated by multi-ple criteria. Many real world problems faced by professionals belong to this category. Solving ill-defined problems is similar to a design process rather than a systematic

Tinkering or Sketching: Apprentices’ Use of Tangibles and Drawings 169

search and the application of well-known procedures. Problem-solvers have to define and frame the problem first and do epistemic monitoring which includes looking for a match between the current definition of the problem and idiosyncratic memories, per-sonal histories, emotional memories and problem-related memories. Design problems are particularly difficult to solve because the quality of a solution cannot be evaluated by standard criteria. Rather, the problem solvers have to define the nature of the prob-lem and deduce relevant evaluation criteria by themselves. Besides individual differ-ences with regards to the expertise in the domain, the problem representation is one of the factors which predict successful problem solving: “An important function of de-signing for problem solving is deciding how to represent the problem to novice learn-ers” ([7], p. 69). Decisions concern the fidelity of the problem representation (e.g. does it present the same complexity as its real-world counterpart) as well as the mo-dality and medium of the representations used.

The particular problem we are interested in is the design of a warehouse. Solving the problem consists of determining the shape, size and placement of different areas (loading docks, merchandise control, storage, administration, order preparation) by taking into account various constraints. The storage area has in turn to be organized as a spatial configuration of shelves and alleys. Paper and pencil is so far the preferred medium to tackle design problems during the logistics apprenticeship. However, teachers report that apprentices have difficulties in reading and constructing layouts on paper. The aim of our contribution is to illustrate the impact of a tangible external representation on how apprentices solve a warehouse design problem. Our hypothesis is that a small-scale model of the warehouse is better suited for apprentices because it supports the concrete, contextualized and enactive mode of reasoning they use in their daily professional life.

Three properties of tangible user interfaces ([8], [9]) are especially promising in a pedagogical context [10]. First, tangible user interfaces include physical action in the repertoire of learning activities with computers. Not surprisingly the added value of sensori-motor experience is often described in projects involving young children [11]. Children may learn through the manipulation of objects by what Piaget called empiri-cal abstraction [12], the idea that one accommodates behavioral schemes in response to resistance from the physical world. The greater “richness” of interaction in terms of perceptual modalities is also put forward as a potential benefit of tangible user inter-faces. The deep immersion into concrete physical experience and the full embodiment of representations might however be counter-productive if the goal of the activity is to foster reflection [13]. The problem might be that the learners get stuck in the action with the tool “ready-at-hand” rather than seeing the concept which it represents (the tool is “present-at-hand”). Similarly, research on manipulatives used in mathematical education has shown that focusing on the manipulative rather than on what it repre-sents is detrimental to learning [14]. Second, the coupling of tangible user interfaces with augmented reality (the system projects information on top of physical artifacts) allows for a very close mapping between tangible input and digital output, between the physicality of an object, the manipulations it affords, and the abstraction of visu-alization. Third, tangible user interfaces naturally support face to face collaborative activities, allowing multiple users to interact with the system at the same time.


3 Method

We follow the approach outlined by the Design-Based Research Collective [15] which consists in testing and building working theories to make sense of a field of investiga-tion through an iterative design and intervention cycle. Wang and Hannafin [16] sum-marize the key points of the approach as 1) it aims at refining both theory and practice 2) through interventions which are grounded in theories and take place in real-world settings 3) with an active participation of the participants in the design 4) through itera-tive cycles of analysis, design, implementation and redesign 5) by the use of an array of methods from field observations to controlled surveys 6) leading to results which are articulated to the specific context of the studies. Our investigation follows these princi-ples rather than a series of tightly controlled laboratory studies. Given the exploratory nature of our hypothesis we do not base our quest for answers on the statistical refuta-tion of hypotheses but rather on a systematic description of observational data.

3.1 Material

A tabletop small-scale warehouse model is built by placing wooden shelves on a 2 by 1.5 meter table, we called TinkerTable. Metallic pillars are used as architectural constraints and rectangular cardboard elements represent specialized areas of a ware-house, like offices and technical rooms. All objects are tagged with fiducial markers (similar to a 2 dimensional bar code) which enable a camera to track their position on the table [17]. The whole model is scaled at 1:16 which allows building the equivalent of a 32 by 24 meters warehouse. The physical warehouse is augmented through a video projector and a mirror placed above the table (see Fig. 1). A gallows carries the cam-era, the video projector and a mirror. The purpose of the mirror is to augment the dis-tance between the projector and the table, in order for the projection to cover the

Fig. 1. Left: The TinkerTable system with the table and the gallows. Wooden shelves are ar-ranged on the table. Right: Five apprentices discuss and draw a forklift’s path on the floor of the warehouse.


whole surface of the table. The table is covered with whiteboard material, which al-lows users to draw by using regular whiteboard markers.

Augmentation through the projector enables the system to draw on top and around the wooden shelves as they are moved on the table. The simplest augmentation con-sists of drawing the navigation path around each shelf. When two shelves are placed too close, the navigation path disappears and signals that a forklift can’t navigate be-tween the shelves. It is therefore possible for users to find the ideal spacing between shelves (i.e. the corridor width) by trial and error. Other features of the layout are rep-resented as well, for instance whether a given shelf is accessible from the loading dock or how long it takes for a forklift to reach the shelf.

3.2 Data Sources

The TinkerTable was tested with apprentices on six occasions which differ according to the location (at the professional school, at the university), the group of students and the teachers involved and the type of augmentations provided by the system. All ses-sions started with the layout of a warehouse by the apprentices. The warehouse was then used as a basis to address further topics in logistics (e.g. optimal placement of goods in the warehouse, optimal picking path for forklifts). The activities were video-taped and sound was recorded with ad hoc microphones. The warehouse layout exer-cise consists of accommodating as many shelves as possible in the given area by taking into account architectural constraints (pillars), placing and dimensioning an administrative area, and placing loading docks. The layout was evaluated by counting the number of accessible pallets and discussing the quality and usability of the ware-house (e.g. navigation, average path length to reach shelves, etc.). The layouts pro-duced by apprentices during these sessions were however not formally sanctioned by a mark.

To enable a comparison with the traditional version of the warehouse layout exer-cise, we conducted an observation during a problem solving session in a class from another school which never used the tabletop simulation. The observation included short interviews with five groups of apprentices and the collection of drawings pro-duced by the apprentices during the design task. This warehouse layout exercise was done in class during four one hour sessions. Groups of three to four apprentices were given the task to design the layout of a warehouse which accommodates a given num-ber of constraints (number of pallets, number of pallets in one shelf, dimension of a shelf, width of alleys, areas for administration and technical rooms, etc.). As an out-come, apprentices delivered a 2D plan of the warehouse, answered a set of arithmetic questions (e.g. how many people are needed to run the warehouse given the time re-quired to pick pallets and the number of movements per day) and had to justify their design. This small report was assessed by a mark.

3.3 Data Analysis

Although the two situations we described differ in a number of ways, we found that an analysis of the drawings produced on paper and the comments gathered during the interviews reveal the potential advantages and disadvantages of the tangible approach. To facilitate and systematize the comparison, we organize the description of each


situation into three sections which correspond to the phases of design problem solving described by Chandrasekaran [18]: Propose, Verify, Modify. Accordingly, the Pro-pose subtask consists of proposing potential solutions. The Verify subtask checks whether relevant design specifications are satisfied. If this is not the case, a diagnosis is performed and the Modify subtask is activated to change the design accordingly. These different phases do not take place in a strict sequential order during problem-solving, and apprentices usually move freely from one to the other, iterating between proposal and verification phases.

4 Results

We now report examples and observations which illustrate how the representational modality affects apprentice’s problem-solving process.

4.1 Paper Modality

Propose. The apprentices are given a set of constraints which can’t directly be mapped onto the problem space: their first task consists of computing the storage area required for the warehouse given the available constraints (store 1500 pallets on shelves with 6 levels of a given width). Once the initial computation is done, appren-tices can determine the scale of their drawing given the size of the paper or the size of the rectangle they chose to represent the warehouse. The problem then consists of segmenting the space by taking into account the relative surface and the arrangement of the areas (e.g. the order preparation zone should be connected with the loading docks). Coming up with a good solution satisfying these constraints seems to pose

Fig. 2. Spatial warehouse configuration which respects surface constraints but without integra-tion into a rectangular shape


great problems to the apprentices, who tend to reproduce the layout of the warehouse they work in at their company. Moreover, dealing with proportions seems to be diffi-cult for them: the typical and intuitive shape of a warehouse is a rectangle, with a ratio of two-third between its width and length, and apprentices naturally tend to (and should) create warehouses following this pattern. The challenge here comes from the fact that the instructions they have only describe the area of the different rooms, which means that their width and length have to be defined to get the given surface and fit altogether in a rectangle. Fig. 2 shows an example of a group of apprentices who had problems in arranging the rooms in rectangles of the correct surface and fi-nally simplified the problem by using only square rooms and thus creating a ware-house with an unpractical shape.

Verify. Evaluating a design drawn on paper implies that the apprentices imagine the work processes, simulating in their head the typical trajectory of a pallet in the ware-house, as well as its implications on the job of workers. It appears that apprentices have problems in doing this as they are often not able to identify clear weaknesses of their designs. The implementation phase gives a clear illustration of the difficulty

Fig. 3. An example of a completed warehouse layout with labeling inconsistencies. (A1) and (A2) are geometrically equal but have been given different values. (A3) and (A4) represent the outside dimensions of the warehouse: the labels define (A4) as being longer than (A3) which is geometrically clearly wrong.


faced by apprentices to handle the abstract representation of a warehouse on paper. Drawing a layout while respecting the relative proportions of the rooms and objects represented was a challenge for most of the groups we interviewed. A closer look to their productions reveals inconsistencies between the layout and a real warehouse. Fig. 3 is an example of a layout on which a group of apprentices we interviewed was working. Two observations are worth noting: the same distance is labeled with two different values, 6m and 51m, and the width (horizontal axis) is labeled as being smaller than the height (vertical axis). Beyond the spatial inconsistencies, the teachers report that apprentices often have difficulties evaluating the quality of their solution with regards to warehouse efficiency.

Modify. Sketching was observed only on few artifacts produced by the apprentices. By their blurriness and fuzziness, sketches signal openness for change and would al-low for exploration of the design space. However, it looks like apprentices try to draw the final plan during their first (and only) proposal. They use drawings as a way to communicate a solution rather than a way to build it. Accordingly, their drawings are done with much emphasis on precision (i.e. using a ruler to draw lines, following the grid on the paper). Drawing “perfect” warehouses leaves no room for modification. Revisions of the design, when they exist, are implemented by drawing a new version of the layout.

4.2 Tangible Modality

Propose. During the observations of apprentices designing a warehouse using the TinkerTable, we noticed that they tended to start implementing their solution almost immediately, without much discussion. Compared to the paper condition where they spend more time thinking about the global organization of the warehouse, the physical objects encourage them to act immediately. The proposal takes place at a more local level, based on the shelves already present on the table. Once the first few shelves are placed by one apprentice, the others simply extend the row of shelves by following the same direction. The implementation phase appeared to be facilitated by the use of physical objects and augmentations. Apprentices can use the shelves’ physical resis-tance as a help for alignment and spacing. Finally, it is worth noting that sometimes several apprentices simultaneously place shelves in different locations on the table.

Verify. Ensuring that the width of the alleys was large enough to allow forklifts to access the content of the shelves was achieved in various ways. In some cases, the system projected circles in front of each shelf. The color of the circles indicated whether the content of the shelf was accessible or not from the loading docks. In some other cases, no information was provided, and apprentices had to use either a pro-jected grid to estimate the distance between the shelves or use a small-scale model of a forklift as a measuring device. These techniques were used for fine-tuning (in order to minimize the space used by alleys), as apprentices were able to visually estimate the optimal width an alley while placing the shelves on the table.

Estimating proportions using physical objects was not a problem for apprentices. It seems that the concrete three-dimensional shape of the shelves helped apprentices to build a representation of the situation that could be easily linked to their experience. For example, on one occasion an apprentice critiqued the position of a shelf a peer


just added by saying: “It doesn’t work like that, if there are several forklifts working, it won’t be wide enough!” The instructions that were given to the apprentices were to design a warehouse with the biggest storage capacity, without worrying about work efficiency as an evaluation criterion. This comment was thus triggered from the ex-perience of this apprentice, who had the feeling that putting this shelf at that place would be a problem for the workers. This example illustrates how the concrete repre-sentation provided by the small-scale model allowed apprentices to think about the warehouse they were building as an authentic workplace.

Modify. As mentioned previously, apprentices were not taking a global approach for designing the layout of the warehouse but were mainly acting at a local level, adding one shelf at a time. The revision phase was thus spread over the whole activity, with apprentices often trying several possibilities before adding a shelf. One interesting property of the tangible approach is that it allowed them to quickly test whether a given position would be acceptable for a shelf. However, global revisions did not happen naturally and apprentices tended to stick to their initial design decisions. The teachers had an important role to play in discussing the production of the apprentices to point out different ways of considering the problem and thus orienting them to-wards another solution. This was made possible by the fact that the first design itera-tion was done rather quickly which saved time to try out other options and discuss them through debriefing sessions.

On one occasion, a teacher was discussing with a group of apprentices about the position where the reception and expedition docks should be placed. Each apprentice proposed and commented on different ideas, and one of them took his own company as an example, which triggered a ten minutes long exchange with the teacher. After watching the videotape of this example, the teachers were positively surprised as they felt that this apprentice would not have engaged in such a detailed description in a traditional classroom situation. It is also worth noting that these explanations took place around an empty table and that gesturing was used to “draw” an invisible warehouse.

5 Discussion

The observations and interviews allowed us to identify main differences between the tangible and paper-based problem representations that influence problem-solving activities.

The first difference concerns the extraction of information from the problem state for verification. The level of metaphor differs among the two forms of representation: the tangible objects give a concrete representation of a warehouse, in three dimen-sions, compared to the more abstract and two-dimensional representation offered by the drawings. The cognitive effort required from the apprentices to work on a paper-based representation of a warehouse is thus stronger, as this form of representation implies a transformation in dimension (from 3D to 2D) and scale compared to the tabletop environment which just implies a change of scale from a real warehouse. In the tabletop environment the scaling is facilitated because the wooden shelves serve as a measuring unit to estimate the size of the warehouse, the relative area of the of-fice, the width of the alleys. The three dimensional nature of shelves, plastic pallet


and miniature forklift allows to use familiar objects to estimate distances. On the con-trary, on paper, all objects are represented as rectangles without a perceptual property that allows differentiating among them. Labels placed on the rectangles allow disam-biguating the meaning of the representations, but do not afford the direct comparison of proportions. These examples illustrate the fact that a drawing of a warehouse lay-out on paper is a disembodied representation for apprentices, who do not seem able to relate it to a real situation.

The second difference concerns the production and modification of design propos-als. Apprentices are not at ease with sketching. One of them told us in a quippy comment: “we are not architects”. As a consequence they do not use sketching (i.e. making rudimentary drawings without paying much attention to details) as a way to explore variations of their current design. The ability to explore design options by sketching requires that designers apprehend the object without attending too much to details. This abstraction allows them to manipulate the essential features of the prob-lem. Buxton’s observation that “[…] it takes the same kind of learning to acquire the skills to converse fluently with a sketch as it takes to learn to speak in any other for-eign language” [19, p.118] concurs with the difficulties that we observed. Tangible shelves are a much less generic expression media compared to pencils. It is not possi-ble to express a design proposal with tangible shelves without actually implementing it in full detail. In other terms, tangible shelves present a minimal level of metaphor as they resemble very closely to their real counterpart [20]. The small scale model we use relies on a metaphor where the user doesn’t need to make an analogy between the virtual and physical world: the effects of moving a wooden shelf are similar in both cases. The metaphor has a positive impact on the ability of apprentices to tackle the design activity: they do not need to maintain the semantic link between the represen-tation and what is represented. Rather than proposing the “big picture”, they proceed in a bottom-up construction of the solution by incrementally adding shelves on the table.

The placement of a shelf is often accompanied by some tinkering, which allows the apprentice to test small variations on the current state of the solution. Especially when they reach a bottleneck (e.g. there is not enough room to place a shelf at the end of a row, a pillar is in the way), these variations trigger a bigger re-arrangement of the warehouse.

6 Conclusion

It appears from our observations that apprentices benefit in two ways from the realism of the small-scale model. First, the 3D representation facilitates the evaluation of the design because relevant spatial features are made salient. Second, the limited expres-siveness of the 3D representation, allows apprentices to concentrate on trying out so-lutions rather than on creating the artifact to represent the solution. We do not claim however that apprentices should stay confined in the concrete manipulation of tangi-bles. Rather, we think that tangibles act as a scaffold which allows apprentices to en-gage with the problem. The pitfalls of tangible interfaces pointed out by Marshall [13] still have to be avoided by appropriately supporting reflection. For instance, teachers perform epistemic monitoring and verify the design through discussions with the


apprentices. Those discussions are a privileged way to illustrate theoretical concepts, because they are embedded in the authentic context of a design problem.

Current extensions of the TinkerTable system include the ability for the system to recognize draw-erase pen annotations on and around wooden shelves. The goal is to enable apprentices to switch back and forth between tangible manipulation and pen-based sketching as well as formal calculations. We recently observed a combination of the two media in a small informal experiment that we conducted in a doctoral course for computer scientists. Students were asked to design a warehouse. Contrary to the apprentices, who built an entire warehouse before entering verification, the computer science students built a small shelf module with tangibles and then used pencil and paper to do calculations to check whether the module could be replicated across the warehouse. This fluid alternance between local and global problem-solving examplifies well the type of skills we try to help apprentices acquire.

Acknowledgments. This research was supported by a grant of the Swiss Federal Of-fice for Professional Education and Technology (OPET). We also thank teachers from the professional school for their readiness an enthusiasm to support our work.

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