Face of Sascha Beckers

Sascha Beckers

Diploma Thesis Student

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My theses was supervised by Jonathan Diehl and Prof. Habel from the Department of Psychiatry and Psychotherapy at Aachen University Hospital.

Time-Based Decision Trees in Interaction Design

This thesis describes the design of the Presentation Visual Editor, a new user interface for the stimulus delivery and experimental control software system Presentation. The Visual Editor is a graphical development environment for the creation of psychological experiments. It allows the visual creation of experiment structures and direct layout of visual stimuli.

The design is based on time-based decision trees which are used to model time structures in interactions. Time-based decision trees are graph representations of hierarchical decision rule systems that include time conditions.

Before starting the development of the system, I conducted a Contextual Inquiry to get an understanding of the psychological domain and to learn about the users’ working methods and problems in the operation of Presentation. The users were observed in the field while implementing experiments.

The design was evolved in three cycles of an iterative user-centered design process. In the first iteration, a paper prototype was designed to test the users' understanding of the concept and to collect fundamental feedback about the interactions of the interface. This paper prototype was then refined and evaluated again in the next iteration. Finally, I have implemented a working interactive prototype in Java to test the interface in more detail.

A final evaluation compared the Presentation Visual Editor with Presentation’s original interface and measured the performance of the design. This study showed that time-based decision trees are beneficial for the design of psychological experiments. The thesis closes with a discussion of the significance of the results for general interaction design.

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  • Sascha Beckers. Time-Based Decision Trees in Interaction Design. Master's Thesis, RWTH Aachen University, Aachen, Germany, July 2008.
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