The inferred mode protocol uses contextual reasoning and local mediators to eliminate the need to access specific modes to perform draw, select, move and delete operations in a sketch interface. In this paper, we describe an observational experiment to understand the learnability, user preference and frequency of use of mode inferencing in a sketch application. The experiment demonstrated that those participants instructed in the interface features liked the fluid transitions between modes. As well, interaction techniques were not self-revealing: Participants who were not instructed in interaction techniques took longer to learn about inferred mode features and were more negative about the interaction techniques. Over multiple sketching sessions, as users develop expertise with the system, we find that they combine inferred mode techniques to speed interaction, and frequently make use of scratch space on the display to retrain themselves and to tune their behaviors. Our results inform the design of sketch interface techniques that incorporate noncommand features.

Matei Negulescu, Jaime Ruiz, and Edward Lank. 2010. Exploring usability and learnability of mode inferencing in pen/tablet interfaces. In Proceedings of the Seventh Sketch-Based Interfaces and Modeling Symposium (SBIM '10). Eurographics Association, Aire-la-Ville, Switzerland, Switzerland, 87-94

@inproceedings{Negulescu:2010:EUL:1923363.1923379,
 author = {Negulescu, M. and Ruiz, J. and Lank, E.},
 title = {Exploring usability and learnability of mode inferencing in pen/tablet interfaces},
 booktitle = {Proceedings of the Seventh Sketch-Based Interfaces and Modeling Symposium},
 series = {SBIM '10},
 year = {2010},
 isbn = {978-3-905674-25-5},
 location = {Annecy, France},
 pages = {87--94},
 numpages = {8},
 url = {http://dl.acm.org/citation.cfm?id=1923363.1923379},
 acmid = {1923379},
 publisher = {Eurographics Association},
 address = {Aire-la-Ville, Switzerland, Switzerland},
}