When fielding satisfaction questions, survey platforms offer the option to randomly reverse the response options. In this paper, we provide evidence that the use of this option leads to biased results. In Study 1, we show that reversing vertically oriented response options leads to significantly lower satisfaction ratings – from 90 to 82 percent in our case. Study 2 had survey respondents verify their response and found that on a reversed scale, the very-dissatisfied option was selected unintentionally in about half of the cases. The cause, shown by Study 3, is that survey respondents expect the positive option at the top and do not always pay sufficient attention to the question, combined with the similar spelling of satisfied and dissatisfied. To prevent unintentional responses from biasing the results, we recommend keeping the positive option at the top in vertically-oriented scales with visually-similar endpoint labels.

Traditionally, the efficiency and effectiveness of search systems have both been of great interest to the information retrieval community. However, an in-depth analysis of the interaction between the response latency and users' subjective search experience in the mobile setting has been missing so far. To address this gap, we conduct a controlled study that aims to reveal how response latency affects mobile web search. Our preliminary results indicate that mobile web search users are four times more tolerant to response latency reported for desktop web search users. However, when exceeding a certain threshold of 7-10 sec, the delays have a sizeable impact and users report feeling significantly more tensed, tired, terrible, frustrated and sluggish, all which contribute to a worse subjective user experience.

Not all smartphone owners use their device in the same way. In this work, we uncover broad, latent patterns of mobile phone use behavior. We conducted a study where, via a dedicated logging app, we collected daily mobile phone activity data from a sample of 340 participants for a period of four weeks. Through an unsupervised learning approach and a methodologically rigorous analysis, we reveal five generic phone use profiles which describe at least 10% of the participants each: limited use, business use, power use, and personality- & externally induced problematic use. We provide evidence that intense mobile phone use alone does not predict negative well-being. Instead, our approach automatically revealed two groups with tendencies for lower well-being, which are characterized by nightly phone use sessions.

We analyzed 794,525 notifications from 278 mobile phone users and how they were handled. Our study advances prior analyses in two ways: first, we systematically split notifications into five categories, including a novel separation of messages into individual- and group messages. Second, we conduct a comprehensive analysis of the behaviors involved in attending the notifications. Our participants received a median number of 56 notifications per day, which does not indicate that the number of notifications has increased over the past years. We further show that messaging apps create most of the notifications, and that other types of notifications rarely lead to a conversion (rates between ca. 15 and 25%). A surprisingly large fraction of notifications is received while the phone is unlocked or the corresponding app is in foreground, hinting at possibility to optimize for this scenario. Finally, we show that the main difference in handling notifications is how long users leave them unattended if they will ultimately not consume them.

Learning a foreign language is a daunting and time-consuming task. People often lack the time or motivation to sit down and engage with learning content on a regular basis. We present an investigation of microlearning sessions on mobile phones, in which we focus on session triggers, presentation methods, and user context. Therefore, we built an Android app that prompts users to review foreign language vocabulary directly through notifications or through app usage across the day. We present results from a controlled and an in-the-wild study, in which we explore engagement and user context. In-app sessions lasted longer, but notifications added a significant number of "quick" learning sessions. 37.6% of sessions were completed in transit, hence learning-on-the-go was well received. Neither the use of boredom as trigger nor the presentation (flashcard and multiple-choice) had a significant effect. We conclude with implications for the design of mobile microlearning applications with context-awareness.

Push notifications are increasingly being used to engage users with app content. In the present research, we propose that users' current affect (i.e., how they are feeling) should be a critical---yet underexplored---factor in user engagement. Participants (N = 337) downloaded a custom-developed app that delivered notifications. After attending to a notification (N = 32,704), participants reported how they felt and chose whether to engage with further content; they could choose between mentally demanding or simple/diverting tasks. When feeling good, people were less likely to engage with mentally demanding tasks. When feeling calm, people were more likely to engage with diverting tasks. When feeling energetic, people were less likely to respond to distractions altogether. These findings provide a tantalizing first glimpse into how affect predicts the kind of content users choose to engage with, paving the way for the use of affect in the design of notification systems.

We report from the Do Not Disturb Challenge where 30 volunteers disabled notification alerts for 24 hours across all devices. The effect of the absence of notifications on the participants was isolated through an experimental study design: we compared self-reported feedback from the day without notifications against a baseline day. The evidence indicates that notifications have locked us in a dilemma: without notifications, participants felt less distracted and more productive. But, they also felt no longer able to be as responsive as expected, which made some participants anxious. And, they felt less connected with one's social group. In contrast to previous reports, about two third of the participants expressed the intention to change how they manage notifications. Two years later, half of the participants are still following through with their plans.

We report from an eye-tracking experiment with 104 participants who performed reading tasks on the most popular text-heavy website of the Web: Wikipedia. Using a hybrid-measures design, we compared objective and subjective readability and comprehension of the articles for font sizes ranging from 10 to 26 points, and line spacings ranging from 0.8 to 1.8 (font: Arial). Our findings provide evidence that readability, measured via mean fixation duration, increased significantly with font size. Further, comprehension questions had significantly more correct responses for font sizes 18 and 26. For line spacing, we found marginal effects, suggesting that the two tested extremes (0.8 and 1.8) impair readability. These findings provide evidence that text-heavy websites should use fonts of size 18 or larger and use default line spacing when the goal is to make a web page easy to read and comprehend. Our results significantly differ from previous recommendations, presumably, because this is the first work to cover font sizes beyond 14 points.

Mobile technology is becoming a loyal companion in our lives. It is used for increasing amounts of time during the day and night, enabling the development of intelligent user interfaces that characterize their users' traits and adapt to them. In this paper, we show how an individual's tendency to experience boredom, i.e. the personal trait called boredom proneness, affects the use of technology -- specifically a smartphone. We develop machine learning models to automatically classify individuals into high/low boredom proneness from their typical daily patterns of smartphone use. We thus propose boredom proneness as a trait with high potential to enable the design of personalized mobile services that are more meaningful to their users.

Boredom is a common human emotion which may lead to an active search for stimulation. People often turn to their mobile phones to seek that stimulation. In this paper, we tackle the challenge of automatically inferring boredom from mobile phone usage. In a two-week in-the-wild study, we collected over 40,000,000 usage logs and 4398 boredom self-reports of 54 mobile phone users. We show that a user-independent machine-learning model of boredom --leveraging features related to recency of communication, usage intensity, time of day, and demographics-- can infer boredom with an accuracy (AUCROC) of up to 82.9%. Results from a second field study with 16 participants suggest that people are more likely to engage with recommended content when they are bored, as inferred by our boredom-detection model. These findings enable boredom-triggered proactive recommender systems that attune their users' level of attention and need for stimulation.

Social norm has it that people are expected to respond to mobile phone messages quickly. We investigate how attentive people really are and how timely they actually check and triage new messages throughout the day. By collecting more than 55,000 messages from 42 mobile phone users over the course of two weeks, we were able to predict people's attentiveness through their mobile phone usage with close to 80% accuracy. We found that people were attentive to messages 12.1 hours a day, i.e. 84.8 hours per week, and provide statistical evidence how very short people's inattentiveness lasts: in 75% of the cases mobile phone users return to their attentive state within 5 minutes. In this paper, we present a comprehensive analysis of attentiveness throughout each hour of the day and show that intelligent notification delivery services, such as bounded deferral, can assume that inattentiveness will be rare and subside quickly.

In this paper we present a method which aims to improve the spelling of children with dyslexia through playful and targeted exercises. In contrast to previous approaches, our method does not use correct words or positive examples to follow, but presents the child a misspelled word as an exercise to solve. We created these training exercises on the basis of the linguistic knowledge extracted from the errors found in texts written by children with dyslexia. To test the effectiveness of this method in Spanish, we integrated the exercises in a game for iPad, DysEggxia (Piruletras in Spanish), and carried out a within-subject experiment. During eight weeks, 48 children played either DysEggxia or Word Search, which is another word game. We conducted tests and questionnaires at the beginning of the study, after four weeks when the games were switched, and at the end of the study. The children who played DysEggxia for four weeks in a row had significantly less writing errors in the tests that after playing Word Search for the same time. This provides evidence that error-based exercises presented in a tablet help children with dyslexia improve their spelling skills.

Mobile instant messaging (e.g., via SMS or WhatsApp) often goes along with an expectation of high attentiveness, i.e., that the receiver will notice and read the message within a few minutes. Hence, existing instant messaging services for mobile phones share indicators of availability, such as the last time the user has been online. However, in this paper we not only provide evidence that these cues create social pressure, but that they are also weak predictors of attentiveness. As remedy, we propose to share a machine-computed prediction of whether the user will view a message within the next few minutes or not. For two weeks, we collected behavioral data from 24 users of mobile instant messaging services. By the means of machine-learning techniques, we identified that simple features extracted from the phone, such as the user's interaction with the notification center, the screen activity, the proximity sensor, and the ringer mode, are strong predictors of how quickly the user will attend to the messages. With seven automatically selected features our model predicts whether a phone user will view a message within a few minutes with 70.6% accuracy and a precision for fast attendance of 81.2%

Notifications are a core feature of mobile phones. They inform users about a variety of events. Users may take immediate action or ignore them depending on the importance of a notification as well as their current context. The nature of notifications is manifold, applications use them both sparsely and frequently. In this paper we present the first large-scale analysis of mobile notifications with a focus on users' subjective perceptions. We derive a holistic picture of notifications on mobile phones by collecting close to 200 million notifications from more than 40,000 users. Using a data-driven approach, we break down what users like and dislike about notifications. Our results reveal differences in importance of notifications and how users value notifications from messaging apps as well as notifications that include information about people and events. Based on these results we derive a number of findings about the nature of notifications and guidelines to effectively use them.

We contribute evidence to which extent sensor- and contextual information available on mobile phones allow to predict whether a user would pick up a call or not. Using an app publicly available for Android phones, we logged anonymous data from 31311 calls of 418 different users. The data shows that information easily available in mobile phones, such as the time since the last call, the time since the last ringer mode change, or the device posture, can predict call availability with an accuracy of 83.2% (Kappa = .646). Personalized models can increase the accuracy to 87% on average. Features related to when the user was last active turned out to be strong predictors. This shows that simple contextual cues approximating user activity are worthwhile investigating when designing context-aware ubiquitous communication systems.

Notifications on mobile phones alert users about new messages, emails, social network updates, and other events. However, little is understood about the nature and effect of such notifications on the daily lives of mobile users. We report from a one-week, in-situ study involving 15 mobile phones users, where we collected real-world notifications through a smartphone logging application alongside subjective perceptions of those notifications through an online diary. We found that our participants had to deal with 63.5 notifications on average per day, mostly from messengers and email. Whether the phone is in silent mode or not, notifications were typically viewed within minutes. Social pressure in personal communication was amongst the main reasons given. While an increasing number of notifications was associated with an increase in negative emotions, receiving more messages and social network updates also made our participants feel more connected with others. Our findings imply that avoiding interruptions from notifications may be viable for professional communication, while in personal communication, approaches should focus on managing expectations.

We report from a study exploring the boundaries of the peripheral perception of vibro-tactile stimuli. For three days, we exposed 15 subjects to a continual vibration pattern that was created by a mobile device worn in their trouser pocket. In order to guarantee that the stimuli would not require the subjects' focal attention, the vibration pattern was tested and refined to minimise its obtrusiveness, and during the study, the participants adjusted its intensity to just above their personal detection threshold. At random times, the vibration stopped and participants had to acknowledge these events as soon as they noticed them. Only 6.5% of the events were acknowledged fast enough to assume that the cue had been on the focus of the participants' attention. The majority of events were answered between 1 and 10 minutes, which indicates that the participants were aware of the cue without focussing on it. In addition, participants reported not to be annoyed by the signal in 94.4% of the events. These results provide evidence that vibration patterns can form non-annoying, lightweight information displays, which can be consumed at the periphery of a user's attention.

Travelers sometimes need to reach a destination in a given amount of time. However, today's navigation systems try to route users to the destination as fast as possible. In this paper, we present the concept of time-based pedestrian navigation. We use a map on a smartphone that highlights streets depending on whether they will lead to a destination in time. Our map also allows the users to choose between route alternatives during the walk.

In this paper, we report about a large-scale in-situ study of tactile feedback for pedestrian navigation systems. Recent advances in smartphone technology have enabled a number of interaction techniques for smartphone that use tactile feedback to deliver navigation information. The aim is to enable eyes-free usage and avoid distracting the user from the environment. Field studies where participants had to fulfill given navigation tasks, have found these techniques to be efficient and beneficial in terms of distraction. But it is not yet clear whether these findings will replicate in in-situ usage. We, therefore, developed a Google Maps-like navigation application that incorporates interaction techniques proposed in previous work. The application was published for free on the Android Market and so people were able to use it as a navigation system in their everyday life. The data collected through anonymous monitoring suggests that tactile feedback is successfully adopted in one third of all trips and has positive effects on the user's level of distraction.

We present PocketMenu, a menu optimized for non-visual, in-pocket interaction with menus on handheld devices with touch screens. By laying out menu items along the border of the touch screen its tactile features guide the interaction. Additional vibro-tactile feedback and speech allows identifying the individual menu items non-visually. In an experiment, we compared PocketMenu with iPhone's VoiceOver. Participants had to control an MP3 player while walking down a road with the device in the pocket. The results provide evidence that in the above context the PocketMenu outperforms VoiceOver in terms of completion time, selection errors, usability. Hence, it enables usage of touch screen apps in mobile contexts (e.g. walking, hiking, or skiing) and limited interaction spaces (e.g. device resting in a pocket).

Going on excursions to explore unfamiliar environments by bike is a popular activity in many places in this world. To investigate the nature of exploratory bicycle trips, we studied tourists on their excursions on a famous vacation island. We found that existing navigation systems are either not helpful or discourage exploration. We therefore propose Tacticycle, a conceptual prototype of a user interface for a bicycle navigation system. Relying on a minimal set of navigation cues, it helps staying oriented while supporting spontaneous navigation and exploration at the same time. In cooperation with a bike rental, we rented the Tacticycle prototype to tourists who took it on their actual excursions. The results show that they always felt oriented and encouraged to playfully explore the island, providing a rich, yet relaxed travel experience. On the basis of these findings, we argue that exploratory trips can be very well supported by providing minimal navigation cues only.

One of the bottlenecks in today's pedestrian navigation system is to communicate the navigation instructions in an efficient but non-distracting way. Previous work has suggested tactile feedback as solution, but it is not yet clear how it should be integrated into handheld navigation systems to improve efficiency and reduce distraction. In this paper we investigate augmenting and replacing a state of the art pedestrian navigation system with tactile navigation instructions. In a field study in a lively city centre 21 participants had to reach given destinations by the means of tactile, visual or multimodal navigation instructions. In the tactile and multimodal conditions, the handheld device created vibration patterns indicating the direction of the next waypoint. Like a sixth sense it constantly gave the user an idea of how the route continues. The results provide evidence that combining both modalities leads to more efficient navigation performance while using tactile feedback only reduces the user's distraction.

This article reports on a preliminary study, which investigates if vibration and speech feedback can be used in order to make a digital map on a touch screen device more accessible. We test if vibration feedback combined with speech, triggered as the finger moves over relevant map objects, works to make sense of the map content. The study results indicate that it is indeed possible to get a basic overview of the map layout even if a person does not have access to the visual presentation. In the conclusions the interaction problems are indentified and suggestions for future improvements are given.

A group of friends visiting a crowded and noisy music festival is an example of a situation where knowing the location of other people is important, but where external factors, such as darkness or noise, can limit the ability to keep track of the others. By combining theories about situation awareness and cognitive processing we inferred that communicating information via the sense of touch is a promising approach in such situations. We therefore investigated how to present the location of several people using a tactile torso display. In particular we focused on encoding spatial distances in the tactile signals. We experimentally compared encoding spatial distances in the rhythm, duration, and intensity of a tactile signal. Our findings show that all parameters are suited to encode distances. None of it was clearly outperformed. We then embedded our tactile location encoding into a fast-paced 3D multiplayer game. In this game, team play and the awareness of the team members' locations are crucial for the success in the game. The results provides evidence that the locations of the team members could be processed effectively despite the game's high cognitive demands. In addition, the team equipped with the tactile display showed a better team play and a higher situation awareness.

The goal of this full-day workshop is to initiate a discussion on the design and presentation of audio and haptic spatial information on mobile devices. We would like to invite researchers working in the fields of human-computer interaction, computer science, cognitive sciences, psychology, psychophysics, and mechatronics to submit a position paper and/or a demo presentation dealing with topics such as methodologies for representing multisensory spatial information on mobile devices, new interaction techniques, specific evaluation methods.

Pedestrian navigation systems are becoming popular but the currently dominant audio-visual interaction can have drawbacks. Tactile feedback is studied as a solution, but currently only available as research prototypes. With the PocketNavigator we propose a demonstrator that adds tactile feedback to a simple but robust map-based navigation system that runs on any Android Smartphone. Users can leave the device in the pocket, while being guided non-visually through vibration cues. Like a compass we "point at" the next waypoint by encoding its direction and distance in vibration patterns. As an advantage over previous approaches it allows giving continuous feedback instead of isolated turning instructions and it can be realized without custom-built tactile displays. Preliminary results from a field study show that pedestrian can effectively use this Tactile Compass to reach a destination without turn-by-turn instructions. Integrated into the PocketNavigator we can now deploy it at the Android Market to evaluate the Tactile Compass with a wide range of users.

Music is a fundamental part of most cultures. Controlling music playback has commonly been used to demonstrate new interaction techniques and algorithm. In particular, controlling music playback has been used to demonstrate and evaluate gesture recognition algorithms. Previous work, however, used gestures that have been defined based on intuition, the developers' preferences, and the respective algorithm's capabilities. In this paper we propose a refined process for deriving gestures from constant user feedback. Along this process a set of free-hand gestures for controlling music playback is developed. The situational context is analyzed to shape the usage scenario and derive an initial set of necessary functions. In a successive user study the set of functions is validated. Furthermore, proposals for gestures are collected from the participants for each function. Two gesture sets containing static and dynamic gestures are derived and analyzed in a comparative evaluation. The evaluation shows that we developed an appropriate set of free-hand gestures for music playback. Our results indicate that the proposed process, that includes validation of each design decision, improves the final results.

This paper describes a novel tool for eliciting user requirements early in the design process of mobile applications. The "Mobile Oracle", as we have called it, is intended to help developers and designers obtain a better understanding of what the user wants at different points in space and time. It is an extension of a lo-fi version of the well-established Wizard of Oz technique, but it adds an "on demand" component to force users to explicitly request the information they need. The technique has been tested in an investigation involving 15 users (sighted, visually impaired, and elderly). Our preliminary results show it to generate valuable information concerning the ways people ask about directions and distances, as well as the services they would like to have in future mobile applications.

Paper maps are a proven means for navigating in unfamiliar environments, however, they do not prevent people from getting lost or taking unwanted detours. A well-known issue is interpreting the map's geocentric content, which is known to become prone to errors when the map is not aligned to the environment. In this paper we report our investigation of providing a cue about the destination's location from an egocentric perspective in order to improve the interpretation of the map. We used a vibrotactile belt to continuously indicate a destination's direction relative to the user's orientation. In an outdoor field study we compared the performance of map-based navigation with and without the added tactile cue. We found evidence that people take shorter routes, consult the map less often, and were less often disoriented with the tactile cue. Furthermore, females found the tactile cue more useful and used it more often.

Cycling is a common leisure time sports in touristic regions. For us it was the question how tourists actually find their paths in the area and what kind of navigation aids might be helpful to them. In a requirements study on a touristic island we learned that tourists rather explore the environment spontaneously than efficiently navigating from on place to another such as the beach or the light house, and just cycle on without much map or navigation aid. While exploring the area, the cyclists however, sometimes lose their orientation which they compensate for by accepting detours. We designed and developed an orientation aid, Tacticycle that does not influence the cycling experience but improve the orientation and awareness of the overall direction. In order to ensure the cyclists' safety two vibrotactile actuators are used to indicate directions and announce the presence of interesting places. In two field studies we showed that despite the accuracy of the indicated direction being rather coarse, the tactile user interface allows cyclists to reach a presented destination easily. The visitor of the demo can experience a virtual cycling tour supported by the Tacticycle demonstrator.