Category Archives: multi-touch

Book Chapter: Input/Output Devices and Interaction Techniques, Third Edition

Thumbnail for Computing Handbook (3rd Edition)Hinckley, K., Jacob, R., Ware, C. Wobbrock, J., and Wigdor, D., Input/Output Devices and Interaction Techniques. Appears as Chapter 21 in The Computing Handbook, Third Edition: Two-Volume Set, ed. by Tucker, A., Gonzalez, T., Topi, H., and Diaz-Herrera, J. Published by Chapman and Hall/CRC (Taylor & Francis), May 13, 2014.  [PDF – Author’s Draft – may contain discrepancies]

Invited Talk: WIPTTE 2015 Presentation of Sensing Techniques for Tablets, Pen, and Touch

The organizers of WIPTTE 2015, the Workshop on the Impact of Pen and Touch Technology on Education, kindly invited me to speak about my recent work on sensing techniques for stylus + tablet interaction.

One of the key points that I emphasized:

To design technology to fully take advantage of human skills, it is critical to observe what people do with their hands when they are engaged in manual activites such as handwriting.

Notice my deliberate the use of the plural, hands, as in both of ’em, in a division of labor that is a perfect example of cooperative bimanual action.

The power of crayon and touch.

My six-year-old daughter demonstrates the power of crayon and touch technology.

And of course I had my usual array of stupid sensor tricks to illustrate the many ways that sensing systems of the future embedded in tablets and pens could take advantage of such observations. Some of these possible uses for sensors probably seem fanciful, in this antiquated era of circa 2015.

But in eerily similar fashion, some of the earliest work that I did on sensors embedded in handheld devices also felt completely out-of-step with the times when I published it back in the year 2000. A time so backwards it already belongs to the last millennium for goodness sakes!

Now aspects of that work are embedded in practically every mobile device on the planet.

It was a fun talk, with an engaged audience of educators who are eager to see pen and tablet technology advance to better serve the educational needs of students all over the world. I have three kids of school age now so this stuff matters to me. And I love speaking to this audience because they always get so excited to see the pen and touch interaction concepts I have explored over the years, as well as the new technologies emerging from the dim fog that surrounds the leading frontiers of research.

Harold and the Purple Crayon book coverI am a strong believer in the dictum that the best way to predict the future is to invent it.

And the pen may be the single greatest tool ever invented to harness the immense creative power of the human mind, and thereby to scrawl out–perhaps even in the just-in-time fashion of the famous book Harold and the Purple Crayon–the uncertain path that leads us forward.

If you are an educator seeing impacts of pen, tablet, and touch technology in the classroom, then I strongly encourage you to start organizing and writing up your observations for next year’s workshop. The 2016 edition of the series will be held at Brown University in Providence, Rhode Island, and chaired by none other than the esteemed Andries Van Dam, who is my academic grandfather (i.e. my Ph.D. advisor’s mentor) and of course widely respected in computing circles throughout the world.

Thumbnail - WIPTTE 2015 invited TalkHinckley, K., WIPTTE 2015 Invited Talk: Sensing Techniques for Tablet + Stylus Interaction. Workshop on the Impact of Pen and Touch Technology on Education, Redmond, WA, April 28th, 2015. [Slides (.pptx)] [Slides PDF]

Project: Bimanual In-Place Commands

Here’s another interesting loose end, this one from 2012, which describes a user interface known as “In-Place Commands” that Michel Pahud, myself, and Bill Buxton developed for a range of direct-touch form factors, including everything from tablets and tabletops all the way up to electronic whiteboards a la the modern Microsoft Surface Hub devices of 2015.

Microsoft is currently running a Request for Proposals for Surface Hub research, by the way, so check it out if that sort of thing is at all up your alley. If your proposal is selected you’ll get a spiffy new Surface Hub and $25,000 to go along with it.

We’ve never written up a formal paper on our In-Place Commands work, in part because there is still much to do and we intend to pursue it further when the time is right. But in the meantime the following post and video documenting the work may be of interest to aficionados of efficient interaction on such devices. This also relates closely to the Finger Shadow and Accordion Menu explored in our Pen +Touch work, documented here and here, which collectively form a class of such techniques.

While we wouldn’t claim that any one of these represent the ultimate approach to command and control for direct input, in sum they illustrate many of the underlying issues, the rich set of capabilities we strive to support, and possible directions for future embellishments as well.

Thumbnail for In-Place CommandsKnies, R. In-Place: Interacting with Large Displays. Reporting on research by Pahud, M., Hinckley, K., and Buxton, B. TechNet Inside Microsoft Research Blog Post, Oct 4th, 2012. [Author’s cached copy of post as PDF] [Video MP4] [Watch on YouTube]

In-Place Commands Screen Shot

The user can call up commands in-place, directly where he is working, by touching both fingers down and fanning out the available tool palettes. Many of the functions thus revealed act as click-through tools, where the user may simultaneously select and apply the selected tool — as the user is about to do for the line-drawing tool in the image above.

Watch Bimanual In-Place Commands video on YouTube

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: 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

GroupTogether — Exploring the Future of a Society of Devices

My latest paper discussing the GroupTogether system just appeared at the 2012 ACM Symposium on User Interface Software & Technology in Cambridge, MA.

GroupTogether video available on YouTube

I’m excited about this work — it really looks hard at what some of the next steps in sensing systems might be, particularly when one starts considering how users can most effectively interact with one another in the context of the rapidly proliferating Society of Devices we are currently witnessing.

I think our paper on the GroupTogether system, in particular, does a really nice job of exploring this with strong theoretical foundations drawn from the sociological literature.

F-formations are small groups of people engaged in a joint activity.

F-formations are the various type of small groups that people form when engaged in a joint activity.

GroupTogether starts by considering the natural small-group behaviors adopted by people who come together to accomplish some joint activity.  These small groups can take a variety of distinctive forms, and are known collectively in the sociological literature as f-formations. Think of those distinctive circles of people that form spontaneously at parties: typically they are limited to a maximum of about 5 people, the orientation of the partipants clearly defines an area inside the group that is distinct from the rest of the environment outside the group, and there are fairly well established social protocols for people entering and leaving the group.

A small group of two users as sensed by GroupTogether's overhead Kinect depth-cameras

A small group of two users as sensed via GroupTogether’s overhead Kinect depth-cameras.

GroupTogether also senses the subtle orientation cues of how users handle and posture their tablet computers. These cues are known as micro-mobility, a communicative strategy that people often employ with physical paper documents, such as when a sales representative orients a document towards to to direct your attention and indicate that it is your turn to sign, for example.

Our system, then, is the first to put small-group f-formations, sensed via overhead Kinect depth-camera tracking, in play simultaneously with the micro-mobility of slate computers, sensed via embedded accelerometers and gyros.

The GroupTogether prototype sensing environment and set-up

GroupTogether uses f-formations to give meaning to the micro-mobility of slate computers. It understands which users have come together in a small group, and which users have not. So you can just tilt your tablet towards a couple of friends standing near you to share content, whereas another person who may be nearby but facing the other way — and thus clearly outside of the social circle of the small group — would not be privy to the transaction. Thus, the techniques lower the barriers to sharing information in small-group settings.

Check out the video to see what these techniques look like in action, as well as to see how the system also considers groupings of people close to situated displays such as electronic whiteboards.

The full text of our scientific paper on GroupTogether and the citation is also available.

My co-author Nic Marquardt was the first author and delivered the talk. Saul Greenberg of the University of Calgary also contributed many great insights to the paper.

Image credits: Nic Marquardt

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