Slide rule: making mobile touch screens accessible to blind people using multi-touch interaction techniques.

Shaun K. Kane, Jeffrey P. Bigham, and Jacob O. Wobbrock.


In October 2008 at ASSETS, Shaun Kane, Jeff Bigham, and Jacob Wobbrock described their work on an experimental screen reader system called Slide Rule. The paper took a risk, studying a technology, touchscreen devices, that seemed inherently inaccessible to blind users and demonstrated convincingly that they could be made accessible. Many of the ideas in Slide Rule appear in Apple’s built-in screen reader, VoiceOver, and VoiceOver has been a transformative technology for blind people.

In the paper, Kane, Bigham, and Wobbrock describe a system of touchscreen gestures to interact with an app and the app would respond in speech to support the interaction. Beyond the invention, they executed a user study with 10 blind individuals on three accessible touchscreen apps for phone, e-mail, and music player, comparing with similar apps for the Pocket PC with the Mobile Speak Pocket screen reader. The user study confirmed that Slide Rule worked; it was useful.

Before the introduction of VoiceOver, this paper publicly demonstrated that touchscreen devices could be made to be accessible to blind users. Remarkably, the touchscreen gestures explored in the paper are among those that are used in VoiceOver. They are very natural, after all. Whether or not the Slide Rule paper influenced the design of VoiceOver, we don’t know. The impact of this paper is evidenced by the number of citations it has, 356 (as of July 11, 2019), as found on Google Scholar. According to the ACM Digital Library record of the paper, it has been cited 128 times (as of July 11, 2019) in ACM sponsored journals and conferences. This includes 25 ASSETS, 10 CHI, and 4 TACCESS citations. The paper has been downloaded 3,418 times (as of July 11, 2019). According to Semantic Scholar the paper has 30 Highly Influential Citations (HIC), more than any other paper ever published at ASSETS.

 Shaun K. Kane (left), Jacob O. Wobbrock (middle) and Jeffrey P. Bigham (right) accepting the 2019 SIGACCESS ASSETS Impact Award (Image Source:
Shaun K. Kane (left), Jacob O. Wobbrock (middle) and Jeffrey P. Bigham (right) accepting the 2019 SIGACCESS ASSETS Impact Award (Image Source:

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Recent advances in touch screen technology have increased the prevalence of touch screens and have prompted a wave of new touch screen-based devices. However, touch screens are still largely inaccessible to blind users, who must adopt error-prone compensatory strategies to use them or find accessible alternatives. This inaccessibility is due to interaction techniques that require the user to visually locate objects on the screen. To address this problem, we introduce Slide Rule, a set of audio-based multi-touch interaction techniques that enable blind users to access touch screen applications. We describe the design of Slide Rule, our interaction techniques, and a user study in which 10 blind people used Slide Rule and a button-based Pocket PC screen reader. Results show that Slide Rule was significantly faster than the button-based system, and was preferred by 7 of 10 users. However, users made more errors when using Slide Rule than when using the more familiar button-based system.

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