Paper Reading #5: Weight-shifting mobiles: two-dimensional gravitational displays in mobile phones

Comments
Cindy Skack
Joshua Penick



Reference Information
Title: Weight-shifting mobiles: two-dimensional gravitational
        displays in mobile phones

Authors: Fabian Hemmert, Deutsche Telekom Laboratories, Berlin,  Germany
              Josefine Zeipelt, Deutsche Telekom Laboratories, Berlin,  Germany
              Susann Hamann, Deutsche Telekom Laboratories, Berlin,  Germany
              Gesche Joost, Deutsche Telekom Laboratories, Berlin,  Germany
              Matthias Lowe, Deutsche Telekom Laboratories, Berlin,  Germany
Presentation Venue: CHI 2010: 28th ACM Conference on Human Factors in Computing Systems;
Date: April 10-15, 2010;
Location: Atlanta, GA, USA

Summary

This is the second paper that I have read from  the authors cited above. .The organization of the paper is similar to the earlier one titled: "Shape-changing mobiles: tapering in two-dimensional deformational displays in mobile phones". While the first paper studied shape-changing mobiles, this one studies weight-shifting mobiles. It is another novel type of haptic feedback, that changes the gravitational properties of the phone by shifting an internal weight along two axes. To evaluate its utility, the authors conducted performance studies with the help of users, as well as qualitative studies. Three domains of application are suggested for this system: Augmenting digital content with physical mass, ambient displays, and haptically augmented wayfinding.

As mentioned earlier, the organization of the paper is similar to the previous one I read.

The authors start out with background information on current works that have been done relating to this application. They mention :

• Force-feedback Displays which offer sensomotory feedback but are not mobile
• Vibrotactile Actuation, which is widely used like for tactile-feedback with mobile touch-screen applications  
• Mass-Based Displays that is more novel and less researched. It studies mainly inertia-based displays.

Three types of applications were proposed for this system: GUI augmentation, ambient display, and haptic pointing. In GUI augmentation, the contents of the device's screen are physically augmented with mass. Ambient display tries to provide an alternatice to the traditional vibrating mechanism, with a weight-shifting solution. Haptic pointing explores allowing the user to point towards things that are outside of the device and get feedback via weight.

For their studies 12 users participated to assess how precise and quickly users could assess the position of the weight in the mobile. The authors report that users were able to determine the position of the weight inside the device with an average erorr of 28.9 mm on the device's X axis, and 21.0 mm on the Y axis. The average time for this task took 6.31s. The qualititative results reveal users prefer the shape-shifting solution as opposed to a weight-shifting solution. In the paper, the authors provide other useful results, and statistics, and suggest that weight-shifting could be a usefule haptic feedback solution but that shape-shifting is more popular amongst users.

They do however point out two things to explain why users may have preferred their shape-shifting solution:

• The weight-shifting mobile is bulky, and oversized as opposed to the shape-shifting mobile
• When doing the experiments, users were not allowed to hold the mobile while it was changing weight.

Discussion

As mentioned before, I had heard of the authors' research before, and had watched one of their presentations they did at the TED conference. This paper confirms the results from the previous one on shape-shifting mobiles: People fancy a shape-shifting solution as opposed to a weight-shifting mobile.
I could see how that could be the case. Feeling an object in one's hand, rather than feeling the weight, provides more useful information to the user in my opinion.