Haptic recognition of shapes at different scales: A comparison of two methods of interaction Mounia Ziat * , Olivier Gapenne, John Stewart, Charles Lenay Pierre Guillaumat Research Center – UTC, Dep. TSH – K102, 60203, Compiegne cedex, France Received 21 February 2006; received in revised form 23 July 2006; accepted 23 July 2006 Available online 8 September 2006 Abstract In order to design a ‘‘haptic zoom’’, in this fundamental study, we compare two scaling methods by focusing on the strategies adopted by subjects who are using a sensory substitution device. Method 1 consists of a reduction of the sensor size and of its displacement speed. Speed reduction is obtained by a ‘‘human’’ movement adjustment (hand speed reduction). Method 2 consists of a straightforward increase in the dimensions of the image. The experimental device used couples a pen on a graphics tablet with tactile sensory stimulators. These are activated when the sensor impinges on the outline of the figure on the computer screen. This virtual sensor (a square matrix composed of 16 elementary fields) moves when the pen, guided by human hand movements, moves on the graphics tablet. The results show that the recognition rate is closely dependent on the size of the figure, and that the strategies used by the subjects are more suitable for method 2 than for method 1. In fact, half of the subjects found that method 1 inhibited their movements, and the majority of them did not feel the scaling effect, whereas this was clearly felt in method 2. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Sensory substitution; Zooming interfaces; Personal Digital Assistants (PDA); Haptic perception 1. Introduction Today, mobile technologies and in particular cellular phones and PDAs (Personal Digital Assistants) occupy an important place in everyday life. Belonging to the cate- gory of ‘‘handheld appliances’’, PDAs are increasingly used for the multiple services that they offer. Note-taking, spreadsheets, agendas, address books, e-mail, web naviga- tion, multimedia players and the consultation of geograph- ical maps are all applications which one can find on a PDA and also in some cellular phones. However the main draw- backs of these systems include processor speed, storage capacity and the size and the resolution of the screen. These disadvantages limit the amount of information that can be stored and visualized on a PDA. In addition to the limitations of the traditional WIMP (Windows, Icons, Menus, and Pointing) model, limitations which also afflict nomadic interfaces, the visualization of information on these devices is even more restricted because of their small displays. Visualization models that differ from this traditional model (Beaudouin-Lafon, 2000) would, however, appear to be a solution to this prob- lem. New paradigms of interaction and visualization using a zoom function, such as zoomable user interfaces (ZUIs), have proved to be very relevant for navigation in sign spac- es (semantic zoom) and graphical objects (geometrical zoom). Much theoretical, ergonomic and computer science programming research has been carried out regarding the possibility of multi-scale navigation (Bederson et al., 2000; Pook et al., 2000). Several pieces of research (Bederson et al., 2002; Jern et al., 2003; Kwang and Grice, 2003) have already intro- duced ZUIs into PDAs, while trying to propose efficient solutions for interaction. People using a zoomable user interface were better at navigating than those using a 0953-5438/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.intcom.2006.07.004 * Corresponding author. Tel.: +33 3 44 23 44 23/post: 5146. E-mail address: mounia.ziat@utc.fr (M. Ziat). URL: http://www3c.utc.fr/~ziatmoun (M. Ziat). www.elsevier.com/locate/intcom Interacting with Computers 19 (2007) 121–132