Pressure as a non-dominant hand input modality for bimanual interaction techniques on touchscreen tablets

McLachlan, Ross David (2015) Pressure as a non-dominant hand input modality for bimanual interaction techniques on touchscreen tablets. PhD thesis, University of Glasgow.

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Touchscreen tablet devices present an interesting challenge to interaction designers: they are not quite handheld like their smartphone cousins, though their form factor affords usage away from the desktop and other surfaces, requires a user to support a larger weight and navigate more screen space. Thus, the repertoire of touch input techniques is often reduced to those performable with one hand. Previous studies have suggested there are bimanual interaction techniques that offer both manual and cognitive benefits over equivalent unimanual techniques and that pressure is useful as a primary input modality on mobile devices and as an augmentation to finger/stylus input on touchscreens. However, there has been no research on the use of pressure as a modality to expand the range of bimanual input techniques on tablet devices.

The first two experiments investigated bimanual scrolling on tablet devices, based on the premise that the control of scrolling speed and vertical scrolling direction could be thought of as separate tasks and that the current status quo of combining both into a single one- handed (unimanual) gesture on a touchscreen or on physical dial can be improved upon. Four bimanual scrolling techniques were compared to two status quo unimanual scrolling techniques in a controlled linear targeting task. The Dial and Slider bimanual technique was superior to the others in terms of Movement Time and the Dial and Pressure bimanual technique was superior in terms of Subjective Workload, suggesting that the bimanual scrolling techniques are better than the status quo unimanual techniques in terms of both performance and preference.

The same interaction techniques were then evaluated using a photo browsing task that was chosen to resemble the way people browse their music collections when they are unsure about what they are looking for. These studies demonstrated that pressure is a more effective auxiliary modality than a touch slider in the context of bimanual scrolling techniques. These studies also demonstrated that the bimanual techniques did not provide any concrete benefits over the Unimanual touch scrolling technique, which is the status quo scrolling technique on commercially available touchscreen tablets and smartphones, in the context of an image browsing task.

A novel investigation of pressure input was presented where it was characterised as a transient modality, one that has a natural inverse, bounce-back and a state that only persists during interaction. Two studies were carried out investigating the precision of applied pressure as part of a bimanual interaction, where the selection event is triggered by the dominant hand on the touchscreen (using existing touchscreen input gestures) with the goal of study- ing pressure as a functional primitive, without implying any particular application. Two aspects of pressure input were studied – pressure Targeting and Maintaining pressure over time. The results demonstrated that, using a combination of non-dominant hand pressure and dominant-hand touchscreen taps, overall pressure targeting accuracy was high (93.07%). For more complicated dominant-hand input techniques (swipe, pinch and rotate gestures), pressure targeting accuracy was still high (86%). The results demonstrated that participants were able to achieve high levels of pressure accuracy (90.3%) using DH swipe gestures (the simplest gesture in the study) suggesting that the ability to perform a simultaneous combination of pressure and touchscreen gesture input depends on the complexity of the dominant hand action involved.

This thesis provides the first detailed study of the use of non-dominant hand pressure input to enable bimanual interaction techniques for tablet devices. It explores the use of pressure as a modality that can expand the range of available bimanual input techniques while the user is seated and comfortably holding the device and offers designers guidelines for including pressure as a non-dominant hand input modality for bimanual interaction techniques, in a way that supplements existing dominant-hand action.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: HCI, pressure input, isometric force, touchscreen, touchscreen tablet, bimanual interaction, two-handed input, non-dominant hand, transience, touchscreen gestures, scrolling, browsing media collections, scrolling techniques, dial
Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Colleges/Schools: College of Science and Engineering > School of Computing Science
Supervisor's Name: Brewster, Professor Stephen
Date of Award: 2015
Depositing User: Ross D McLachlan
Unique ID: glathesis:2015-6960
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 22 Dec 2015 11:18
Last Modified: 08 Jan 2016 13:05

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