Systems’ latency – the time between user input and system response – slows down the human-computer interaction loop. Several studies revealed negative objective and subjective effects of high latency, typically treating latency as a constant delay. Because latency varies significantly in practice, recent work also assessed the effects of large and sudden latency changes. In practice, however, latency variations are small but frequent. As the effects of such variations are unclear, we investigate how small latency variations (± 50 ms) affect users’ performance and perceived task load for 2D target selection tasks with static and moving targets. For static targets, we found that latency variation causes significantly higher completion times and less efficient trajectories, however with small effect sizes. In contrast, we found no significant effects on any performance measure for moving targets. Our findings indicate that the effect of latency variation is generally very small and quickly disappears for non-trivial tasks.

Touch-sensitive surfaces offer an intuitive and flexible form of interaction, for example through gesture input. Despite being the primary input modality for mobile devices, they hardly find application in desktop settings. At the same time, the computer mouse is still the most efficient and accurate input device for pointing. Consequently, keeping the unmatched functionality of a mouse but extending it with new input options via a touch-sensitive surface, is a promising approach. While research prototypes and niche products for multi-touch mice exist, the concept has not yet become established. In this work, we follow a user-centered approach towards touch interaction on computer mice. In a user study (n=12), we identified which areas on the mouse are suitable for touch input. Further, we explored potential usage scenarios in a diary study (n=11) and intuitive gestures in an elicitation study (n=10). We compile our findings into a gesture set which future research can build upon to implement touch interaction on computer mice.

Tables are focus points for social interactions and support everyday activities, such as learning, crafting, or dining. These physical interactions on and around the table may be augmented with digital information and tools projected onto the tabletop. For interaction with such projected information, touch input suffers from technical and interactional limitations. Pen input is a more robust alternative that does not suffer from Midas-touch problems. We developed a system for tracking the position of an IR-emitting pen tip on a planar surface with sub-millimeter resolution and an end-to-end latency of less than 30 ms. Distinguishing between drawing and hovering states is done by combining a stereoscopic camera setup and a machine-learning classifier. We demonstrate practical performance, uses and limitations through multiple studies and examples.

The latency of a text editor describes how long it takes from pressing a key to the corresponding letter appearing on the screen. It is well known that high latency affects how quickly authors can write and edit texts. In order to quantify the effects of latency on users’ performance and task load, we conducted a study in which 31 participants had to re-type or correct provided texts with a physical keyboard. Each participant completed each task once with a low latency of 20 ms and once with a high latency of 200 ms. We found that latency had no significant effect on users’ performance during the copy task, but correcting texts was affected significantly by high latency. Additionally, our results suggest that fast typers are more likely to notice latency than slow typers. Our findings regarding the effects of text input latency on users’ performance contributes to the existing body of research on latency in interactive systems.

In interactive systems high latency affects user performance and experience. This is especially problematic in video games. A large number of studies on this topic investigated the effects of constant, high latency. However, in practice, latency is never constant but varies by up to 100 ms due to variations in processing time and delays added by polling between system components. In a large majority of studies, these variations in latency are neither controlled for nor reported. Thus, it is unclear to which degree small, continuous variations in latency affect user performance. If these unreported variations had a significant impact, this might cast into doubt the findings of some studies. To investigate how latency variation affects player performance and experience in games, we conducted an experiment with 28 participants playing a first-person shooter. Participants played with two levels of base latency (50 ms vs. 150 ms) and variation (0 ms vs. 50 ms). As expected, high base latency significantly reduces player performance and experience. However, we found strong evidence that small variations in latency in the order of 50 ms, do not affect player performance significantly. Thus, our findings mitigate concerns that previous latency studies might have systematically ignored a confounding effect.

Tangibles are small, graspable objects that act as input devices or physical representations of digital data. Oftentimes, it is desirable to track the position of tangibles on a surface and their relation to each other. However, outside-in tracking techniques - such as capacitive touchscreens or cameras - require setting up elaborate infrastructure and are prone to occlusion or interference. We propose Dothraki, an inside-out tracking technique for tangibles on flat surfaces. An optical mouse sensor embedded in the tangible captures a small (36×36 pixel / 1×1 mm), unique section of a black-and-white De-Bruijn dot pattern printed on the surface. Our system efficiently searches the pattern space in order to determine the precise location of the tangible with sub-millimeter accuracy. Our proof-of-concept implementation offers a recognition rate of up to 95%, robust error detection, an update rate of 14 Hz, and a low-latency relative tracking mode.

We propose a method for accurately and precisely measuring the intrinsic latency of input devices and document measurements for 36 keyboards, mice and gamepads connected via USB. Our research shows that devices differ not only in average latency, but also in the distribution of their latencies, and that forced polling at 1000 Hz decreases latency for some but not all devices. Existing practices - measuring end-to-end latency as a proxy of input latency and reporting only mean values and standard deviations - hide these characteristic latency distributions caused by device intrinsics and polling rates. A probabilistic model of input device latency demonstrates these issues and matches our measurements. Thus, our work offers guidance for researchers, engineers, and hobbyists who want to measure the latency of input devices or select devices with low latency.

In the field of pedestrian navigation some systems use prominent identifying features, so called landmarks. Attributes of high-quality landmarks are recognizability, actuality, uniqueness and noticeability. One of the challenges of this kind of navigation systems is to collect and evaluate landmarks with consistent quality. The system we developed solves these struggles with a crowdsourcing approach. We combine this with gamification elements in order to reach many users and to assure long-term motivation. Our system shows images of existing landmarks to the player, which he is afterwards asked to assign to a map of the university. Depending on the distance of his guess to the real position the player earns points. The application strives to encourage users to upload and rate pictures of existing landmarks. A multiplayer mode which allows challenging other users keeps them involved. In contrast to other products, our system does not rely on localization via GPS. Another goal was to implement a self-running system with a minimal amount of dedicated administration needed. Therefore the users with the highest scores are rating the submitted content.