Watching online videos on mobile devices has been massively present in people's daily activities. However, different users can watch the same video for different purposes, and hence develop different expectations for their experience. Understanding people's motivations for watching videos on mobile can help address this problem by giving designers the information needed to craft the whole watching journey better adapting to user's expectations. To obtain this understanding, a comprehensive framework of viewer motivations is necessary. We present research that provides several contributions to understanding mobile video watchers: a thorough framework of user motivations to watch videos on mobile devices, a detailed procedure for collecting and categorizing these motivations, a set of challenges that viewers experience to address each motivation, insights on usage of mobile and non-mobile devices, and design recommendations for video sharing systems.

In order to better understand social aspects of the short-form video watching experience, we investigated the journey to co-watching, from searching and discovering content, to choosing and experiencing videos with others. After identifying, through a large-scale survey, some of the most typical situations that bring people to YouTube, we deployed a one week-long diary study with 12 participants in which they performed a set of frequent video tasks at their leisure, half by themselves, and half with someone else. Following the diary study, we had participants reenact the diary study tasks remotely with the experimenter. We observed that users face multiple challenges on the journey to co-watching a video. They must share a device designed for an individual, use different methods for selecting videos than when by themselves, negotiate or turn-take in order to make a decision, and potentially watch a video that they do not enjoy. Along this journey, users must engage in impression management to consider how their choices might make them appear to others. We present design recommendations for remote and collocated co-watching to improve the social video watching experience.

We explore how the problem of uncertainty and imprecision in natural language generation (NLG) could be addressed through the use of fuzzy sets. We propose bringing together standard empirical procedures for knowledge acquisition in NLG and computing with words/perceptions related techniques (with a special focus on linguistic description of data) to address an open challenge in NLG: the generation of geographical referring expressions. Following this methodology, we present an exploratory experiment which provides some insights about how human subjects refer to geographical expressions and discuss how the obtained results might relate to the use of fuzzy sets.

This paper discusses the importance of computing relative properties and not just retrieving absolute properties when generating geographic referring expressions such as "northern France".We describe an algorithm that computes spatial properties at run-time by means of spatial operations such as intersecting and analyzing parts of wholes.The evaluation of the algorithm suggests that part-whole relations are key in geographic expressions.

We present findings of a study with 62 subjects who had 796 of their outgoing mobile phone calls recorded and transcribed for their later annotation—by highlighting important information shared during calls. We found that patterns in these calls (numbers, names, interrogative adverbs), as well as some contextual parameters, are better indicators of annotation needs than the callers' profile or call quality. Callers highlight information in both parties' turns (caller and callee) more often than highlighting solely information provided by the callee, which is mostly due to annotating questions with contextual information for the highlights in the callee's turns. We discuss how this behavior changes according to call purpose. Finally, we found that annotation needs change over time: whereas some annotations might not be considered relevant after weeks, others originally considered irrelevant might become important archival notes. We present implications of these findings for the design of mobile phone annotation tools.

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%

In the context of a myriad of mobile apps which collect personally identifiable information (PII) and a prospective market place of personal data, we investigate a user-centric monetary valuation of mobile PII. During a 6-week long user study in a living lab deployment with 60 participants, we collected their daily valuations of 4 categories of mobile PII (communication, e.g. phonecalls made/received, applications, e.g. time spent on different apps, location and media, e.g. photos taken) at three levels of complexity (individual data points, aggregated statistics and processed, i.e. meaningful interpretations of the data). In order to obtain honest valuations, we employ a reverse second price auction mechanism. Our findings show that the most sensitive and valued category of personal information is location. We report statistically significant associations between actual mobile usage, personal dispositions, and bidding behavior. Finally, we outline key implications for the design of mobile services and future markets of personal data.

This paper describes the ongoing imple-mentation and the current coverage of SimpleNLG-BP, an adaptation of Simple-NLG-EnFr (Vaudry and Lapalme, 2013) for Brazilian Portuguese. 1

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.

With the advent of instant mobile messaging applications, traditional SMS is in danger of loosing it's reign as the king of mobile messaging. Applications like WhatsApp allow mobile users to send real-time text messages to individuals or groups of friends at no cost. While there is a vast body of research on traditional text messaging practices, little is understood about how and why people have adopted and appropriated instant mobile messaging applications. The goal of this work is to provide a deeper understanding of the motives and perceptions of a popular mobile messaging application called WhatsApp and to learn more about what this service offers above and beyond traditional SMS. To this end, we present insights from two studies an interview study and a large-scale survey highlighting that while WhatsApp offers benefits such as cost, sense of community and immediacy, SMS is still considered a more reliable, privacy preserving technology for mobile communication.

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.

Most online service providers offer free services to users and in part, these services collect and monetize personally identifiable information (PII), primarily via targeted advertisements. Against this backdrop of economic exploitation of PII, it is vital to understand the value that users put to their own PII. Although studies have tried to discover how users value their privacy, little is known about how users value their PII while browsing, or the exploitation of their PII. Extracting valuations of PII from users is non-trivial - surveys cannot be relied on as they do not gather information of the context where PII is being released, thus reducing validity of answers. In this work, we rely on refined Experience Sampling - a data collection method that probes users to valuate their PII at the time and place where it was generated in order to minimize retrospective recall and hence increase measurement validity. For obtaining an honest valuation of PII, we use a reverse second price auction. We developed a web browser plugin and had 168 users - living in Spain - install and use this plugin for 2 weeks in order to extract valuations of PII in different contexts.

We propose a conceptual model that explains the relationship between the users' personality profile and their satisfaction with basic mobile phone services (calls, messages, and simple GPRS/3G services). The model captures direct and indirect effects on satisfaction by means of two variables: actual mobile phone usage and perceived usability of the related services. We empirically validate the model with data gathered from 603 customers of a telecommunication operator, and find that: (1) extroversion , conscientiousness , and intellect have a significant impact on customer satisfaction—positively for the first two traits and negatively for the latter; (2) extroversion positively influences mobile phone usage; and (3) extroversion and conscientiousness positively influence the users' perceived usability of mobile services. Interestingly, usability has the strongest positive impact on satisfaction, whereas mobile phone usage has a negative impact on satisfaction. We discuss key findings of this model and propose several implications for the design of mobile phone services.

Note-taking has been largely studied in contexts of work meetings. However, often people need to remember information exchanged in informal situations, such as during mobile phone conversations. In this paper we present a study conducted with 59 subjects who had their phone calls semi-automatically transcribed for later annotation. Analysis of the 621 calls and the subjects' annotation behavior revealed that phone recall is indeed a relevant user need. Furthermore, identifying patterns in phone calls such as numbers and names provide better indicators of annotation than variables related to the callers' profile, context of calls, or quality of service. Our findings suggest implications for the design of mobile phone annotation tools.

This paper presents ethnographic observations, a diary study and a large-scale quantitative questionnaire (n=395) designed to study the reasons for adoption and refusal of context-aware mobile applications. Through a qualitative study we identify 24 user needs that these applications fulfill and 9 barriers for adoption. We found that for many of the identified needs the end-goal is not that of receiving information, thus complementing work on mobile information needs. Also, this work offers an actionable list of obstacles that prevent contextual services to reach a larger audience. Finally, our findings suggest the opportunity to develop novel mobile applications that fulfill needs in the activity and personal contextual dimensions, and that of developing an application store for feature phones.

People share pictures online to increase their social presence. However, recent studies have shown that most of the content shared in social networks is not looked at by peers. Proper metadata can be generated and used to improve the retrieval of this content. In spite of this, we still lack solutions for collecting valid descriptors of content that can be used effectively in the context of social information navigation. In this paper, we propose a mechanism based on persuasive techniques to support peers in providing metadata for multimedia content that can be used for a person's self-promotion. Through an iterative design and experimentation process, we demonstrate how this methodology can be used effectively to increase one's social presence thus building more enjoyable, rich, and creative content that is shared in the social network. In addition, we highlight implications that inform the design of social games with a purpose.

Medication compliance is a critical component in the success of any medical treatment. However, only 50% of patients correctly adhere to their prescription regimens. Mobile and ubiquitous technologies have been proposed to tackle this challenge, mainly in the form of memory aid solutions that remind patients to take their pills. However, most of these methods do not engage patients in shifting their behavior towards better compliance. In this paper, we propose and evaluate a mobile phone-based game called MoviPill that persuades patients to be more adherent to their medication prescription by means of social competition. In a 6-week user study conducted with 18 elders, the use of MoviPill improved both their compliance to take the daily medication and also the accuracy of the drug intake time according to the prescribed time. Moreover, the improvement in the latter increased from 43% to 56% when we considered only participants that had any interest in games, which reveals the importance of applying persuasive techniques in a personalized manner. We conclude with a set of implications for the design of persuasive mobile solutions in this domain.

Information overload is one of today's major concerns. As high-resolution digital cameras become increasingly pervasive, unprecedented amounts of social media are being uploaded to online social networks on a daily basis. In order to support users on selecting the best photos to create an online photo album, attention has been devoted to the development of automatic approaches for photo storytelling. In this paper, we present a novel photo collection summarization system that learns some of the users' social context by analyzing their online photo albums, and includes storytelling principles and face and image aesthetic ranking in order to assist users in creating new photo albums to be shared online. In an in-depth user study conducted with 12 subjects, the proposed system was validated as a first step in the photo album creation process, helping users reduce workload to accomplish such a task. Our findings suggest that a human audio/video professional with cinematographic skills does not perform better than our proposed system.

Popular content in video sharing websites (e.g., YouTube) is usually replicated via identical copies or near-duplicates. These duplicates are usually studied because they pose a threat to site owners in terms of wasted disk space, or privacy infringements. Furthermore, this content might potentially hinder the users' experience in these websites. The research presented in this article focuses around the central argument that there is no agreement on the technical definition of what these near-duplicates are, and, more importantly, there is no strong evidence that users of video sharing websites would like this content to be removed. Most scholars define near-duplicate video clips (NDVC) by means of non-semantic features (e.g., different image/audio quality), while a few also include semantic features (i.e., different videos of similar content). However, it is unclear what features contribute to the human perception of near-duplicate videos. The findings of four large scale online surveys that were carried out in the context of our research confirm the relevance of both types of features. Some of our findings confirm the adopted definitions of NDVC whereas other findings are surprising: Near-duplicate videos with different image quality, audio quality, or with/without overlays were perceived as NDVC. However, the same could not be verified when videos differed by more than one of these features at the same time. With respect to semantics, it is yet unclear the exact role that it plays in relation to the features that make videos alike. From a user's perspective, participants preferred in most cases to see only one of the NDVC in the search results of a video search query and they were more tolerant to changes in the audio than in the video tracks. Based on all these findings, we propose a new user-centric NDVC definition and present implications for how duplicate content should be dealt with by video sharing Web sites.

Speech and typed text are two common input modalities for mobile phones. However, little research has compared them in their ability to support annotation and retrieval of digital pictures on mobile devices. In this paper, we report the results of a month-long field study in which participants took pictures with their camera phones and had the choice of adding annotations using speech, typed text, or both. Subsequently, the same subjects participated in a controlled experiment where they were asked to retrieve images based on annotations as well as retrieve annotations based on images in order to study the ability of each modality to effectively support users' recall of the previously captured pictures. Results demonstrate that each modality has advantages and shortcomings for the production of tags and retrieval of pictures. Several guidelines are suggested when designing tagging applications for portable devices.

Popular content in video sharing web sites (e.g., YouTube) is usually duplicated. Most scholars define near-duplicate video clips (NDVC) based on non-semantic features (e.g., different image/audio quality), while a few also include semantic features (different videos of similar content). However, it is unclear what features contribute to the human perception of similar videos. Findings of two large scale online surveys (N = 1003) confirm the relevance of both types of features. While some of our findings confirm the adopted definitions of NDVC, other findings are surprising. For example, videos that vary in visual content - by overlaying or inserting additional information - may not be perceived as near-duplicate versions of the original videos. Conversely, two different videos with distinct sounds, people, and scenarios were considered to be NDVC because they shared the same semantics (none of the pairs had additional information). Furthermore, the exact role played by semantics in relation to the features that make videos alike is still an open question. In most cases, participants preferred to see only one of the NDVC in the search results of a video search query and they were more tolerant to changes in the audio than in the video tracks. Finally, we propose a user-centric NDVC definition and present implications for how duplicate content should be dealt with by video sharing websites.

We present TripleBeat, a mobile phone based system that assists runners in achieving predefined exercise goals via musical feedback and two persuasive techniques: a glanceable interface for increased personal awareness and a virtual competition. TripleBeat is based on a previous system named MPTrain. First, we describe TripleBeat's hardware and software, emphasizing how it differs from its predecessor MPTrain. Then, we present the results of a runner study with 10 runners. The study compared the runners efficacy and enjoyment in achieving predefined workout goals when running with MPTrain and TripleBeat. The conclusions from the study include: (1) significantly higher efficacy and enjoyment with TripleBeat, and (2) a unanimous preference for TripleBeat over MPTrain. The glanceable interface and the virtual competition are the two main reasons for the improvements in the running experience. We believe that systems like TripleBeat will play an important role in enhancing the exercise experience and in assisting users towards more active lifestyles.

This paper clarifies theoretical assumptions about the conceptual multi-device design and presents a practical implementation for e-learning applications. Interfaces are generated automatically for handhelds (smartphone, Pocket PC, etc.) maintaining the desktop look and feel with the same actions flow for a given task. First prototypes were better evaluated than a successful commercial approach. Usability evaluations will be conducted to investigate the advantages of this proposal for the distance learning.