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TU Berlin

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Stefan Schaffer


Research Field


Research Topics

• Multimodal Human-Computer Interaction
• Model-based Usability Evaluation
• User Modeling


Stefan Schaffer studied Communication Science and Computer Science at the Technical University Berlin. In 2009 he completed his degree and received the Willumeit prize for his Magister thesis. He has joined the research training group prometei and is currently working towards his PhD thesis in the domain of model-based usability evaluation of multimodal systems.


Technische Universität Berlin
Zentrum Mensch-Maschine-Systeme
Graduiertenkolleg prometei
Sekretariat FR 2-6
Franklinstr. 28/29
D-10587 Berlin

Tel: +49 (30) 314 - 29637
Fax: +49 (30) 314 - 25996



Modeling Input Modality Choice in Mobile Graphical and Speech Interfaces
Citation key schaffer2015a
Author Schaffer, Stefan and Schleicher, Robert and Möller, Sebastian
Pages 21–34
Year 2015
ISSN 1071-5819
DOI 10.1016/j.ijhcs.2014.11.004
Journal Int. Journal of Human-Computer Studies
Volume 73
Number 3
Month mar
Note print/online
Abstract In this paper, we review three experiments with a mobile application that integrates graphical input with a touch-screen and a speech interface and develop a model for input modality choice in multimodal interaction. The model aims to enable simulation of multimodal human–computer interaction for automatic usability evaluation. The experimental results indicate that modality efficiency and input performance are important moderators of modality choice. Accordingly, we establish a utility-driven model that provides probability estimations of modality usage, based on the parameters of modality efficiency and input performance. Four variants of the model that differ in training data are fitted by means of Sequential Least Squares Programming. The analysis reveals a considerable fit regarding averaged modality usage. When applied to individual modality usage profiles, the accuracy decreases significantly. In an application example it is shown how the modality choice mechanism can be deployed for simulating interaction in the field of automatic usability evaluation. Results and possible limitations are discussed.
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