R. Wasinger and A. Krüger. Modality preference – learning from users. In Proceedings of the User Experience Design for Pervasive Computing workshop, Munich, Germany, 11 May 2005. [PDF]
This paper describes a qualitative comparison of input modalities for mobile applications. The author conducted a user study with about 50 users that were asked to fill questionnaires on a PDA. The questions targeted products that the users could find in a shop and therefore had to be answered while on the place. The users were divided in different groups and each group was exposed to different input modality: speech, handwriting, intra- and extra-gestures.
Interestingly, speech was reported as being the most comfortable modality to use in comparison with handwriting but also the modality that could mostly expose privacy. Users reported being uncomfortable speaking sensible information to their devices. Handwriting was see as conflicting with other manual activities that needed to be carried out while shopping.