Category Archives: Published Papers

Paper: Experimental Study of Stroke Shortcuts for a Touchscreen Keyboard with Gesture-Redundant Keys Removed

Text Entry on Touchscreen Keyboards: Less is More?

When we go from mechanical keyboards to touchscreens we inevitably lose something in the translation. Yet the proliferation of tablets has led to widespread use of graphical keyboards.

You can’t blame people for demanding more efficient text entry techniques. This is the 21st century, after all, and intuitively it seems like we should be able to do better.

While we can’t reproduce that distinctive smell of hot metal from mechanical keys clacking away at a typewriter ribbon, the presence of the touchscreen lets keyboard designers play lots of tricks in pursuit of faster typing performance. Since everything is just pixels on a display it’s easy to introduce non-standard key layouts. You can even slide your finger over the keys to shape-write entire words in a single swipe, as pioneered by Per Ola Kristensson and Shumin Zhai (their SHARK keyboard was the predecessor for Swype and related techniques).

While these type of tricks can yield substantial performance advantages, they also often demand a substantial investment in skill acquisition from the user before significant gains can be realized. In practice, this limits how many people will stick with a new technique long enough to realize such gains. The Dvorak keyboard offers a classic example of this: the balance of evidence suggests it’s slightly faster than QWERTY, but the high cost of switching to and learning the new layout just isn’t worth it.

In this work, we explored the performance impact of an alternative approach that builds on people’s existing touch-typing skills with the standard QWERTY layout.

And we do this in a manner that is so transparent, most people don’t even realize that anything is different at first glance.

Can you spot the difference?

Snap quiz time


What’s wrong with this keyboard?  Give it a quick once-over. It looks familiar, with the standard QWERTY layout, but do you notice anything unusual? Anything out of place?

Sure, the keys are arranged in a grid rather than the usual staggered key pattern, but that’s not the “key” difference (so to speak). That’s just an artifact of our quick ‘n’ dirty design of this research-prototype keyboard for touchscreen tablets.

Got it figured out?

All right. Pencils down.

Time to check your score. Give yourself:

  • One point if you noticed that there’s no space bar.
  • Two points if you noticed that there’s no Enter key, either.
  • Three points if the lack of a Backspace key gave you palpitations.
  • Four points and a feather in your cap if you caught the Shift key going AWOL as well.

Now, what if I also told you removing four essential keys from this keyboard–rather than harming performance–actually helps you type faster?


All we ask of people coming to our touchscreen keyboard is to learn one new trick. After all, we have to make up for the summary removal of Space, Backspace, Shift, and Enter somehow. We accomplish this by augmenting the graphical touchscreen keyboard with stroke shortcuts, i.e. short straight-line finger swipes, as follows:marking-menu-overlay-5

  • Swipe right, starting anywhere on the keyboard, to enter a Space.
  • Swipe left to Backspace.
  • Swipe upwards from any key to enter the corresponding shift-symbol. Swiping up on the a key, for example, enters an uppercase A; stroking up on the 1 key enters the ! symbol; and so on.
  • Swipe diagonally down and to the left for Enter.



In addition to possible time-motion efficiencies of the stroke shortcuts themselves, the introduction of these four gestures–and the elimination of the corresponding keys made redundant by the gestures–yields a graphical keyboard with number of interesting properties:

  • Allowing the user to input stroke gestures for Space, Backspace, and Enter anywhere on the keyboard eliminates fine targeting motions as well as any round-trips necessary for a finger to acquire the corresponding keys.
  • Instead of requiring two separate keystrokes—one to tap Shift and another to tap the key to be shifted—the Shift gesture combines these into a single action: the starting point selects a key, while the stroke direction selects the Shift function itself.
  • Removing these four keys frees an entire row on the keyboard.
  • Almost all of the numeric, punctuation, and special symbols typically relegated to the secondary and tertiary graphical keyboards can then be fit in a logical manner into the freed-up space.
  • Hence, the full set of characters can fit on one keyboard while holding the key size, number of keys, and footprint constant.
  • By having only a primary keyboard, this approach affords an economy of design that simplifies the interface, while offering further potential performance gains via the elimination of keyboard switching costs—and the extra key layouts to learn.
  • Although the strokes might reduce round-trip costs, we expect articulating the stroke gesture itself to take longer than a tap. Thus, we need to test these tradeoffs empirically.


Our studies demonstrated that overall the removal of four keys—rather than coming at a cost—offers a net benefit.

Specifically, our experiments showed that a stroke keyboard with the gesture-redundant keys removed yielded a 16% performance advantage for input phrases containing mixed-case alphanumeric text and special symbols, without sacrificing error rate. We observed these performance advantages from the first block of trials onward.

Even in the case of entirely lowercase text—that is, in a context where we would not expect to observe a performance benefit because only the Space gesture offers any potential advantage—we found that our new design still performed as well as a standard graphical keyboard. Moreover, people learned the design with remarkable ease: 90% wanted to keep using the method, and 80% believed they typed faster than on their current touchscreen tablet keyboard.

Notably, our studies also revealed that it is necessary to remove the keys to achieve these benefits from the gestural stroke shortcuts. If both the stroke shortcuts and the keys remain in place, user hesitancy about which method to use undermines any potential benefit. Users, of course, also learn to use the gestural shortcuts much more quickly when they offer the only means of achieving a function.

Thus, in this context, less is definitely more in achieving faster performance for touchscreen QWERTY keyboard typing.

The full results are available in the technical paper linked below. The paper contributes a careful study of stroke-augmented keyboards, filling an important gap in the literature as well as demonstrating the efficacy of a specific design; shows that removing the gesture-redundant keys is a critical design choice; and that stroke shortcuts can be effective in the context of multi-touch typing with both hands, even though previous studies with single-point stylus input had cast doubt on this approach.

Although our studies focus on the immediate end of the usability spectrum (as opposed to longitudinal studies over many input sessions), we believe the rapid returns demonstrated by our results illustrate the potential of this approach to improve touchscreen keyboard performance immediately, while also serving to complement other text-entry techniques such as shape-writing in the future.

Stroke-Keyboard-GI-2014-thumbArif, A. S., Pahud, M., Hinckley, K., and Buxton, B.,  Experimental Study of Stroke Shortcuts for a Touchscreen Keyboard with Gesture-Redundant Keys Removed In Proc. Graphics Interface 2014 (GI’14).  Canadian Information Processing Society, Toronto, Ont., CanadaMontreal, Quebec, Canada, May 7-9, 2014. Received the Michael A. J. Sweeney Award for Best Student Paper.  [PDF] [Talk Slides (.pptx)] [Video .MP4] [Video .WMV]

Watch A Touchscreen Keyboard with Gesture-Redundant Keys Removed video on YouTube

Paper: Writing Handwritten Messages on a Small Touchscreen

Here’s the final of our three papers at MobileHCI 2013 conference. This was a particularly fun project, spearheaded by my colleague Wolf Kienzle, looking at a clever way to do handwriting input on a touchscreen using just your finger.

In general I’m a fan of using an actual stylus for handwriting, but in the context of mobile there are many “micro” note-taking tasks, akin to scrawling a note to yourself on a post-it, that wouldn’t justify unsheathing a pen even if your device had one.

The very cool thing about this approach is that it allows you to enter overlapping multi-stroke characters using the whole screen, and without resorting to something like Palm’s old Graffiti writing or full-on handwriting recognition.


The interface also incorporates some nice fluid gestures for entering spaces between words, backspacing to delete previous strokes, or transitioning to a freeform drawing mode for inserting little sketches or smiley-faces into your instant messages, as seen above.

This paper also had the distinction of receiving an Honorable Mention Award for best paper at MobileHCI 2013. We’re glad the review committee liked our paper and saw its contributions as noteworthy, as it were (pun definitely intended).

Writing-Small-Touchscreen-thumbKienzle, W., Hinckley, K., Writing Handwritten Messages on a Small Touchscreen. In ACM 15th International Conference on Human-Computer Interaction with Mobile Devices and Services, (MobileHCI 2013), Munich, Germany, Aug. 27-30, 2013, pp. 179-182. Honorable Mention Award (Awarded to top 5% of all papers). [PDF] [video MP4] [Watch on YouTube - coming soon.]

Paper: A Tap and Gesture Hybrid Method for Authenticating Smartphone Users

Tap-Gesture-Authentication-thumbArif, A., Pahud, M., Hinckley, K., Buxton, W., A Tap and Gesture Hybrid Method for Authenticating Smartphone Users (Poster). In ACM 15th International Conference on Human-Computer Interaction with Mobile Devices and Services(MobileHCI 2013), Munich, Germany, Aug. 27-30, 2013, pp. 486-491. [Paper PDF] [Poster Presentation PDF] [Video .WMV] [Video .MP4]

Paper: Toward Compound Navigation Tasks on Mobiles via Spatial Manipulation

I have three papers coming out this week at MobileHCI 2013, the 15th International Conference on Human-Computer Interaction with Mobile Devices and Services, which convenes this week in Munich. It’s one of the great small conferences that focuses exclusively on mobile interaction, which of course is a long-standing interest of mine.

This post focuses on the first of those papers, and right behind it will be short posts on the other two projects that my co-authors are presenting this week.

I’ve explored many directions for viewing and moving through information on small screens, often motivated by novel hardware sensors as well as basic insights about human motor and cognitive capabilities. And I also have a long history in three-dimensional (spatial) interaction, virtual environments, and the like. But despite doing this stuff for decades, every once in a while I still get surprised by experimental results.

That’s just part of what keeps this whole research gig fun and interesting. If the all answers were simple and obvious, there would be no point in doing the studies.

In this particular paper, my co-authors and I took a closer look at a long-standing spatial, or through-the-lens, metaphor for interaction– akin to navigating documents (or other information spaces) by looking through your mobile as if it were a camera viewfinder– and subjected it to experimental scrutiny.

While this basic idea of using your mobile as a viewport onto a larger virtual space has been around for a long time, the idea hasn’t been subjected to careful scrutiny in the context of moving a mobile device’s small screen as a way to view virtually larger documents. And the potential advantages of the approach have not been fully articulated and realized either.

This style of navigation (panning and zooming control) on mobile devices has great promise because it allows you to offload the navigation task itself to your nonpreferred hand, leaving your preferred hand free to do other things like carry bags of grocieries — or perform additional tasks such as annotation, selection, and tapping commands — on top of the resulting views.

But, as our study also shows, it is an approach not without its challenges; sensing the spatial position of the device, and devising an appropriate input mapping, are both difficult challenges that will need more progress to fully take advantage of this way of moving through information on a mobile device. For the time being, at least, the traditional touch gestures of pinch-to-zoom and drag-to-pan still appear to offer the most efficient solution for general-purpose navigation tasks.

Compound-Navigation-Mobiles-thumbPahud, M., Hinckley, K., Iqbal, S., Sellen, A., and Buxton, B., Toward Compound Navigation Tasks on Mobiles via Spatial Manipulation. In ACM 15th International Conference on Human-Computer Interaction with Mobile Devices and Services, (MobileHCI 2013), Munich, Germany, Aug. 27-30, 2013, pp. 113-122. [PDF] [video - MP4]

Toward Compound Navigation on Mobiles via Spatial Manipulation on YouTube

Paper: Motion and Context Sensing Techniques for Pen Computing

I continue to believe that stylus input — annotations, sketches, mark-up, and gestures — will be an important aspect of interaction with slate computers in the future, particularly when used effectively and convincingly with multi-modal pen+touch input. It also seems that every couple of years I stumble across an interesting new use or set of techniques for motion sensors, and this year proved to be no exception.

Thus, it should come as no surprise that my latest project has continued to push in this direction, exploring the possibilities for pen interaction when the physical stylus itself is augmented with inertial sensors including three-axis accelerometers, gyros, and magnetometers.


In recent years such sensors have become integrated with all manner of gadgets, including smart phones and tablets, and it is increasingly common for microprocessors to include such sensors directly on the die. Hence in my view of the world, we are just at the cusp of sensor-rich stylus devices becoming  commercially feasible, so it is only natural to consider how such sensors afford new interactions, gestures, or context-sensing techniques when integrated directly with an active (powered) stylus on pen-operated devices.

In collaboration with Xiang ‘Anthony’ Chen and Hrvoje Benko I recently published a paper exploring motion-sensing capabilities for electronic styluses, which takes a first look at some techniques for such a device. With some timely help from Tom Blank’s brilliant devices team at Microsoft Research, we built a custom stylus — fully wireless and powered by an AAAA battery — that integrates these sensors.

These range from very simple but clever things such as reminding the user if they have left behind the pen — a common problem that users encounter with pen-based devices — to fun new techniques that emulate physical media, such as the gesture of striking a loaded brush on one’s finger in water media.


Check out the video below for an overview of these and some of the other techniques we have come up with so far, or read more about it in the technical paper linked below.

We are continuing to work in this area, and have lots more ideas that go beyond what we were able to accomplish in this first stage of the project, so stay tuned for future developments along these lines.

Motion-Context-Pen-thumbHinckley, K., Chen, X., and Benko, H., Motion and Context Sensing Techniques for Pen
In Proc. Graphics Interface 2013 (GI’13).  Canadian Information Processing Society, Toronto, Ont., CanadaRegina, Saskatchewan, Canada, May 29-31, 2013. [PDF] [video - MP4].

Watch Motion and Context Sensing Techniques for Pen Computing video on YouTube

Paper: Implicit Bookmarking: Improving Support for Revisitation in Within-Document Reading Tasks

The March 2013 issue of the International Journal of Human-Computer Studies features a clever new technique for automatically (implicitly) bookmarking recently-visited locations in documents, which (as our paper reveals) eliminates 66% of all long-distance scrolling actions for users in active reading scenarios.

The technique, devised by Chun Yu (Tsinghua University Department of Computer Science and Technology, Beijing, China) in collaboration with  Ravin Balakrishnan, myself, Tomer Moscovish, and Yuanchun Shi, requires only minimal modification of existing scrolling behavior in document readers — in fact, our prototype works by implementing a simple layer on top of the standard Adobe PDF Reader.

The technique would be particularly valuable for students or information workers whose activities necessitate deep engagements with texts such as technical documentation, non-fiction books on e-readers, or– of course, my favorite pastime– scientific papers.

Implicit Bookmarking prototype and studyYu, C., Balakrishnan, R., Hinckley, K., Moscovich, T.,  Shi, Y., Implicit bookmarking: Improving support for revisitation in within-document reading tasks. International Journal of Human-Computer Studies, Vol. 71, Issue 3, March 2013, pp. 303-320. [Definitive Version] [Author's draft PDF -- may contain discrepancies]

Paper: Gradual Engagement between Digital Devices as a Function of Proximity: From Awareness to Progressive Reveal to Information Transfer

I collaborated on a nifty project with the fine folks from Saul Greenberg’s group at the University of Calgary exploring the emerging possibilities for devices to sense and respond to their digital ecology. When devices have fine-grained sensing of their spatial relationships to one another, as well as to the people in that space, it brings about new ways for users to interact with the resulting system of cooperating devices and displays.

This fine-grained sensing approach makes for an interesting contrast to what Nic Marquardt and I explored in GroupTogether, which intentionally took a more conservative approach towards the sensing infrastructure — with the idea in mind that sometimes, one can still do a lot with very little (sensing).

Taken together, the two papers nicely bracket some possibilities for the future of cross-device interactions and intelligent environments.

This work really underscores that we are still largely in the dark ages with regard to such possibilities for digital ecologies. As new sensors and sensing systems make this kind of rich awareness of the surround of devices and users possible, our devices, operating systems, and user experiences will grow to encompass the expanded horizons of these new possibilities as well.

The full citation and the link to our scientific paper are as follows:

Gradual Engagement with devices via proximity sensingMarquardt, N., Ballendat, T., Boring, S., Greenberg, S. and Hinckley, K., Gradual Engagement between Digital Devices as a Function of Proximity: From Awareness to Progressive Reveal to Information Transfer. In Proceedings of ACM Interactive Tabletops & Surfaces (ITS 2012). Boston, MA, USA, November 11-14. 10pp. [PDF] [video - MP4].

Watch the Gradual Engagement via Proximity video on YouTube

Paper: Cross-Device Interaction via Micro-mobility and F-formations (“GroupTogether”)

GroupTogetherMarquardt, N., Hinckley, K., and Greenberg, S., Cross-Device Interaction via Micro-mobility and F-formations.  In ACM UIST 2012 Symposium on User Interface Software and Technology (UIST ’12). ACM, New York, NY, USA,  Cambridge, MA, Oct. 7-10, 2012, pp. (TBA). [PDF] [video - WMV]. Known as the GroupTogether system.

See also my post with some further perspective on the GroupTogether project.

Watch the GroupTogether video on YouTube

Paper: Informal Information Gathering Techniques for Active Reading

This is my latest project, which I will present tomorrow (May 9th) at the CHI 2012 Conference on Human Factors in Computing Systems.

I’ll have a longer post up about this project after I return from the conference, but for now enjoy the video. I also link to the PDF of our short paper below which has a nice discussion of the motivation and design rationale for this work.

Above all else, I hope this work makes clear that there is still tons of room for innovation in how we interact with the e-readers and tablet computers of the future– as well as in terms of how we consume and manipulate content to produce new creative works.

Informal Information Gathering Techniques for Active ReadingHinckley, K., Bi, X., Pahud, M., Buxton, B., Informal Information Gathering Techniques for Active Reading. 4pp Note. In Proc. CHI 2012  Conf. on Human Factors in Computing Systems, Austin, TX, May 5-10, 2012. [PDF]

[Watch Informal Information Gathering Techniques for Active Reading on YouTube]

Paper: CodeSpace: Touch + Air Gesture Hybrid Interactions for Supporting Developer Meetings

CodeSpace systemBragdon, A., DeLine, R., Hinckley, K., and Morris, M. R., Code space: Touch + Air Gesture Hybrid Interactions for Supporting Developer Meetings.  In Proc. ACM International Conference on Interactive Tabletops and Surfaces (ITS ’11). ACM, New York, NY, USA,  Kobe, Japan, November 13-16, 2011, pp. 212-221. [PDF] [video - WMV]. As featured on Engadget and many other online forums.

Watch CodeSpace video on YouTube