Kamran Sedighian, Faculty of Information and Media
Studies and Department of Computer Science, Middlesex College,
Rm. 355, The University of Western Ontario, London, Ontario, N6A
Tel: (519) 661-2111, ext. 86612
Fax: (519) 661-3515
Maria Klawe, Dean of Science
Rm. 1505, Biological Sciences, 6270 University Blvd., The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
Tel: (604) 822-3337
Fax: (604) 822-0677
Marvin Westrom, Faculty of Education
The University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
Tel: (604) 822-5314
Fax: (604) 822-4714
Software tools are frequently designed using an object-manipulation metaphor. The user manipulates screen objects to indicate the desired operations he or she desires. The better the interface, the more naturally the metaphorthe causal link between screen object and controlled objectis maintained; the user feels that he or she has both control and understanding of the underlying process. Designers strive to make the manipulation process as easy as possible.
The objective of educational software is different. Instead of controlling objects, the user manipulates embedded educational concepts, but these applications can still use the same object-manipulation metaphor.
This study compares three types of object-manipulation interfaces in a program designed to support learning of transformation geometry. Students must arrange seven geometric shapes to complete a tangram puzzle using three standard operations: translation, rotation, or reflection.
The Direct Object Manipulation (DOM) interface enabled students to directly control shapes on the screen. Students could "'grab"' a shape with the mouse and then translate, rotate, or reflect it.
The Direct Concept Manipulation (DCM) interface enabled the user to interact with and manipulate the concepts behind moving the shapes on the screen. Instead of moving the shapes directly, students used a transformation tool. For example, the student selected a shape and the rotation tool. The tool showed a center of rotation, angle of rotation, and a ghost image of the shape in its resultant position. The student manipulated the tool to move the ghost image into the desired position. Pressing "GO" caused the shape to advance smoothly along the tool trajectory to its new location. Figure 1 shows a screen shot of the DCM approach.
The Reflective Direct Concept Manipulation (RDCM) interface required the students to manipulate the concepts in three scaffolded stages. The first step is similar to the DCM described earlier. In the second step, the ghost image is removed, making it necessary for the student to visualize this image and rely more fully on his understanding of the concept. In the third step, the transformation path is also removed, requiring the student to interact with a more abstract representation of the concept in order to achieve the desired transformation. Figure 2 shows the process of concept scaffolding.
A statistically significant effect was observed in our study. Interviews established that the DOM interface presented the least cognitive load; students could quickly use it effectively to work on the tangram puzzles. However, it produced the least amount of learning. The DCM interface was a little more cognitively demanding to use, but resulted in a slightly better understanding of the underlying concepts. The RDCM interface, the most cognitively demanding, resulted in significantly improved learning of transformation geometry.
Some implications of this research for the design of educational interfaces include the following:
- Ease of use of the interface is not the most important criterion.
- Learners would benefit from direct interaction with explicit representations of underlying concepts.
- Learners would benefit from interaction that promotes reflective thought.
- Learners should progressively interact with different layers of meaning embedded in the interface representation.
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