Simone Beets
email: simone.beets2@nmmu.ac.za

Janet Wesson
email: janet.wesson@nmmu.ac.za

Managing Personal Information across Multiple Devices: Challenges and Opportunities

Keywords: Personal Information Management, Multiple Devices, Interview Study

Due to the constantly increasing volume of personal information (PI) and the current trend towards mobile devices, there is a growing need to provide access to PI across multiple devices. It has become difficult for a user to manage his/her PI across these devices. The current hierarchical systems used to organize PI do not support accessing PI across multiple devices. The aim of this paper is to discuss the outcomes of an interview study that was conducted to determine how users currently manage PI across multiple devices and to identify what problems are experienced using these devices. Results showed that participants found it difficult to access PI across their devices and do not know beforehand what information they need to access. These problems could be solved by providing an information visualization tool installed on their devices which provides a single user interface to facilitate an overall view of their PI.

Introduction

Personal information management (PIM) involves the daily activities or tasks that users need to perform using a set of information items, such as documents, media and calendar events [START_REF] Jones | A Report on the NSF-Sponsored Workshop on Personal Information Management[END_REF]. A user's personal information (PI) increases constantly as information is currently being stored on a number of different devices, platforms and applications [START_REF] Aires | Personal Information Dashboard -Me, At a Glance[END_REF]. This has led to a high level of dispersion of PI, referred to as the information fragmentation problem, and an increased difficulty in managing, accessing and using this information. It has become difficult for a user to access to his/her PI at any time regardless on which device the information is stored. The goal of this research is to provide support for accessing PI across multiple personal devices.

The current method used to organize PI is in hierarchies of files and/or folders [START_REF] Golemati | Evaluating the Significance of the Windows Explorer Visualization in Personal Information Management Browsing Tasks[END_REF]. Although the hierarchy is a familiar organization method, it suffers from several limitations due to its restrictive nature [START_REF] Golemati | Evaluating the Significance of the Windows Explorer Visualization in Personal Information Management Browsing Tasks[END_REF]. Current PIM solutions mainly focus on enhancing PIM on a single device or on a subset of PI [START_REF] Tungare | Understanding the Evolution of Users' Personal Information Management Practices[END_REF]. Alternative applications, such as Dropbox (www.dropbox.com) and TeamViewer (www.teamviewer.com), provide support for accessing PI, but also have several shortcomings. The aim of this paper is to describe the results of an interview study that was conducted to determine how participants currently manage PI across different devices and identify the problems that participants experience in managing PI across these devices. The results of this study will inform the design of a tool to support accessing PI across multiple devices using information visualization (IV) techniques.

Section 2 discusses related work regarding PIM. Section 3 introduces the interview study and describes the themes identified from the interview data. Design implications are identified in Section 4 based on the results of the interview study. The paper concludes by discussing the main contribution of this research and future work to be completed.

Related Work

PIM is a large, active area of research [START_REF] Jones | A Report on the NSF-Sponsored Workshop on Personal Information Management[END_REF], [START_REF] Indratmo | A Review of Organizational Structures of Personal Information Management[END_REF]. The goal of PIM is to enable a user to access his/her PI relevant to his/her location, in the most appropriate form, while supporting the tasks of PIM [START_REF] Jones | A Report on the NSF-Sponsored Workshop on Personal Information Management[END_REF]. PIM tasks were originally identified in [START_REF] Barreau | Context as a Factor in Personal Information Management Systems[END_REF] to include acquiring, organizing, storing, maintaining, retrieving and producing PI. PIM tasks were then simplified to include keeping (storing), managing (organizing and maintaining) and finding (searching and browsing for retrieval) [START_REF] Jones | A Report on the NSF-Sponsored Workshop on Personal Information Management[END_REF]. Lower-level PI tasks include creating, sorting, moving, naming, assigning properties, copying, distributing, deleting and transforming PI [START_REF] Jones | A Report on the NSF-Sponsored Workshop on Personal Information Management[END_REF]. The keeping (storing), organizing and finding (viewing and retrieving) PIM tasks across multiple devices form the focus of this paper.

The type of PI organization has a large impact on how the PI is viewed [START_REF] Golemati | Evaluating the Significance of the Windows Explorer Visualization in Personal Information Management Browsing Tasks[END_REF]. Jetter et al. [START_REF] Jetter | ZOIL -A Cross-Platform User Interface Paradigm for Personal Information Management[END_REF] suggested that a user interface (UI) needs to be designed to support accessing PI to assist a user to develop his/her own processes, structures and views. Gomes et al. [START_REF] Gomes | Designing a Personal Information Visualization Tool[END_REF] stated that a meaningful IV technique may be the solution for the difficulty in finding relevant PI.

Interview Study

Interview Method

Face-to-face, one-on-one, in-person, informal, semi-structured interviews were conducted with selected participants [START_REF] Creswell | Research Design: Qualitative, Quantitative, and Mixed Methods Approaches[END_REF]. Thematic analysis, in combination with coding techniques, was used to analyze the interview data. The interview study was used to establish how PI is currently being managed across multiple devices. PI types considered in this study included email, calendar events, document files and media, such as images and video.

The interviews were conducted with ten academic staff and postgraduate students from the Department of Computing Sciences at the Nelson Mandela Metropolitan University (NMMU), using purposive sampling based on the participants' computing knowledge and experience, and their use of multiple devices for PIM. The participants ranged between 21 and 50+ years of age. All participants had at least six years of computer experience and all but one participant managed their PI daily using a digital device.

Four main questions were asked in the interview regarding PIM across multiple devices, which included the following:

Do you have any ideas on how better to manage your PI across these different devices?

Sub-questions: Have you heard of Team Viewer or Dropbox? Do you have any ideas on managing your PI other than using removable drives for file transfer? Would you like a tool that would provide an overview of your PI across your different devices allowing access to this PI? If you would prefer such a tool, would you prefer it to be an application installed on your device or a web-based application that you would use in a browser?

Results

The transcripts of each interview were analyzed with NVivo 10 software (www.qsrinternational.com), using coding techniques to identify themes within the data. The results of the data analysis are described in this section.

Keeping (Storing):

The number and combination of devices and platforms exacerbate the current PIM situation. The participants of the interview study made use of various devices to manage their PI. Most participants of the interview study used at least three devices for PIM, with a few participants using five devices for PIM.

All participants of the interview study used a desktop computer provided by the university for PIM or work-related activities. Additionally, all participants commented on using their devices for a combination of personal-and work-related activities. Nine participants made use of their mobile phone for PIM and eight participants had a desktop computer at home that they used for PIM. Six participants made use of a laptop for PIM.

Nine participants had a combination of devices which made use of different platforms. Five participants considered their desktop computer at the university as their main device used for PIM and work-related tasks. Four participants considered a combination of devices as their main devices for different purposes. Four participants mainly used a laptop when travelling and accessing their PI. Four participants travelled with their mobile phones or netbook computers.

Management: Participants make use of email for access, removable drives for additional storage and transfer, and file managers for organization. Participants mainly used different combinations of methods to manage their PI across their different devices. Participants still currently make use of email to access information on one device from another. Participants also mentioned using removable drives either continuously or at some stage for managing PI across different devices.

All participants made use of the Windows Explorer folder structure provided on their desktop computers and laptop devices to organize their PI. Six participants made use of Dropbox, either as their primary mechanism for accessing information across different devices or as a back-up tool. One participant mentioned that he used the same folder structure on each device to "not get lost": "I have the same folder structure; it's more or less the same. So when I take something in my 'paper folder', I just put it on my 'paper folder' at home. I have that in order not to get lost, because if you have a general folder structure, you will be confused at a certain point of time."

Retrieving: Participants currently find it difficult to access PI across their devices and do not know what they will need to access in future. Participants noted various problems in managing their PI across different devices. Participants identified that the hierarchical folder structure is restrictive mainly due to being limited to categorizing a file in a single folder:

"Finding stuff can sometimes be a problem, or, 'I know I took a photo of this, but now where did I put it?' I actually had that problem the other day, because when I take the stuff off my phone, I don't always put it into the correct place."

Participants experienced problems with naming folders appropriately, especially when backing up information and organizing different versions of PI items. Other issues identified involve versioning issues, having to remember to update folders with the latest files and problems with inconsistent structures between different devices. One participant also mentioned not being able to view information in different ways:

"I organize my photos by dates, events and places, but that gets mixed up sometimes. If I want to have it by date and by location it's difficult. If, for example, for our holiday trips to Knysna, I can't remember what year it was, then it's a pain to go and search each year and check the photo. And then if you do it by location, if you want to find everything that happened last year then you have the other problem, or with people, 'view all the photos that have my little girl in it, that's my bulldog.' Then you have to go and search all the folders…"

Eight participants identified that Dropbox mainly suffers from the same limitations as the Windows Explorer folder structure. Participants identified that a problem with using various methods for organizing files across different devices is that one is re-quired to know beforehand what information is needed to be accessed. A participant noted that he would like all his information to be available: "…I will most certainly not know beforehand, and I would prefer everything to be available."

Participants identified that it is difficult to keep record of different versions of the same PI item. Participants found problems with the email structure and other file structures not being able to communicate, and that email items and other items cannot be linked or associated, as one participant explained: "It would be quite a cool thing if you had this integrated view of all your information, because here you've got the email system, which is one system, and then you've got your file structure on a particular device, which is another system, and yet there could be connections between individual emails and a topic."

One participant described a problem he had recently experienced involving accessing information:

"The other day I needed a file. I was at home and my Internet was giving me hassles. I can VPN from home into this PC fairly easily, if I have the Internet connection. And there I'm sitting; I can't get hold of that file. So, I had to drive in to come and fetch a file here, to go back and work on it. So, that's the kind of problem: having no real time, online access to certain information."

Four participants mentioned the information fragmentation problem, some in terms of examples, including the following scenario:

"Here is where things get tricky, because I've got photos on my phone, I've got photos which are on the office PC, and I've got photos on my laptop. In addition, my wife's netbook has got photos on as well, and one can't easily aggregate them together. You can try and bundle them together but they are so massive, you can't really forward them easily by emailing, so you've got to use a memory stick. Even working across my WiFi network at home would be a bit slow."

Viewing: Participants need an IV tool installed on their devices which provides a single UI to facilitate an overall view of their cross-device PI. This requirement is also supported by literature [START_REF] Jetter | ZOIL -A Cross-Platform User Interface Paradigm for Personal Information Management[END_REF], [START_REF] Gomes | Designing a Personal Information Visualization Tool[END_REF]. Four participants noted that if there was such a tool, they would like it to provide some sort of automation in organizing their PI. Participants preferred the tool to be a native application installed on each device, as a browser may provide limitations for such a tool.

Participants provided various suggestions on how better to manage PI across different devices. Participants suggested a search tool, which is capable of searching across different devices to find information. One participant suggested a tool which would intelligently "think" for the user: "…Maybe also it would remember the things that I did the most, and pre-fetch stuff for me. Rather than saying, 'ok I'm going to give you all this stuff' but 'ok I'm rather going to give you pre-fetched stuff, that I'm watching you and seeing what you're doing', and that would be a cool thing. To be able to see what's there, which I can't do, I can't access the stuff, and I also can't see what's there. I can't picture it. In fact…I can't visualize it."

Design Implications

Several design implications were identified for the IV tool suggested in Section 3.2. These design implications are categorized according to organization, visualization and interaction.

Organization

Provide a virtual storage solution that aggregates PI in a single location.

There is currently limited support for accessing PI across different devices. The virtual storage solution could allow the PI to reside on the original device but aggregate references to PI items, which could be accessed when the different user devices are connected, as suggested in [START_REF] Karypidis | OmniStore: Automating Data Management in a Personal System Comprising Several Portable Devices[END_REF]. This could address the issues identified by participants that they are unsure beforehand which PI items will be needed.

2.

Provide support for association of linked PI items. Supporting linking of PI items could assist with version control of PI. Support for PI item association as used in Phlat [START_REF] Cutrell | Fast, Flexible Filtering with Phlat -Personal Search and Organization Made Easy[END_REF], could also address the issue of not being able to link items of PI collections in separate applications.

3.

Provide tagging to assist with retrieval. Tagging PI items could also assist with version control. Manually and/or automatically tagging PI items could assist with re-finding information when searching, as used in Phlat [START_REF] Cutrell | Fast, Flexible Filtering with Phlat -Personal Search and Organization Made Easy[END_REF].

4. Include additional facilities other than general PI types. In addition to the common PI types, email and contacts were regularly mentioned in the interview study. Contact management is another important task of PIM which should be supported [START_REF] Indratmo | A Review of Organizational Structures of Personal Information Management[END_REF].

Visualization

1. Make use of a single UI to visualize PI across different devices. All participants described scenarios where they experienced information fragmentation problems and nine welcomed the suggestion of a tool that provides a single UI to visualize PI across several devices. Systems, such as Phlat [START_REF] Cutrell | Fast, Flexible Filtering with Phlat -Personal Search and Organization Made Easy[END_REF] and ZOIL [START_REF] Jetter | ZOIL -A Cross-Platform User Interface Paradigm for Personal Information Management[END_REF], provide a single UI for different PI types, but do not fully support cross-device PIM.

2. Visualize PI using suitable IV techniques. It was identified that the list and indented-list may not be suitable for viewing PI. Suitable IV techniques could address the restrictive nature of the hierarchy and its ineffective use of screen space. Timelines have been used in various PIM systems, including VizMe [START_REF] Gomes | Designing a Personal Information Visualization Tool[END_REF].

3. Provide different PI views. Participants noted that only having one view of their PI is not sufficient and that the proposed tool should provide different PI views. It was suggested that while time is useful for PIM, it should not be the only aspect considered [START_REF] Latif | Combining Context Ontology and Landmarks for Personal Information Management[END_REF].

4.

Consider each device's constraints. Eight participants managed their PI across at least three devices. Thus, UI plasticity should be considered to ensure that the UI design will support several different devices. [START_REF] Thevenin | Adaptation and Plasticity of User Interfaces[END_REF].

Interaction

1. Provide intelligent searching across devices. In addition to the IV techniques used to support browsing, intelligent searching of PI also needs to be facilitated. A combination of keyword searching, in-text searching and filters, as used in Phlat [START_REF] Cutrell | Fast, Flexible Filtering with Phlat -Personal Search and Organization Made Easy[END_REF], could be used to allow searching PI across different devices.

2. Provide support for file sharing and collaboration. The current hierarchical organization method, with the exception of tools such as Dropbox, does not support file sharing or collaboration, but needs to be supported by the proposed tool [START_REF] Collins | Collaborative Personal Information Management with Shared, Interactive Tabletops[END_REF].

3. Provide full functionality associated with PI items. Due to the information fragmentation problem, if an item cannot be viewed, it cannot be accessed. The full functionality of each PI item should be facilitated, as supported by ZOIL [START_REF] Jetter | ZOIL -A Cross-Platform User Interface Paradigm for Personal Information Management[END_REF].

4. Support immediate access to PI items. The proposed tool should provide instant access to PI items if the device(s) are available, and could possibly include offline accessibility of certain PI items. Additionally, the UI delay problems experienced using Phlat should be avoided [START_REF] Cutrell | Fast, Flexible Filtering with Phlat -Personal Search and Organization Made Easy[END_REF].

Conclusion

An interview study was conducted to determine how users currently manage PI across different devices and the problems that are experienced with PIM. A limitation of the study was a small sample size (n=10). Participants made use of various combinations of methods to manage their PI across multiple devices. The most popular methods included the use of Email, the folder structure, removable drives and Dropbox. The participants of the interview study identified a number of problems in managing PI, mainly attributed to not being able to view and access PI across different devices. The suggestion of an IV tool to support access to PI across multiple devices received a positive response. The results of the interview study were used to propose several design implications for organization, visualization and interaction. Future work will involve the design of an IV tool to visualize a user's PI across multiple devices, using suitable IV techniques.

1. How many digital devices do you currently use to store PI?

	Sub-questions: What type of device is each of these? What platform(s) does each
	device use? Which is the main device for managing PI? If you travel, which de-
	vice do you take with you? Are your devices used for personal or work infor-
	mation or for a combination?
	2.

How do you currently manage your PI across these devices

?

Sub-questions: If you need information on one device that is stored on another device, how would you go about this process? Do you make use of a file manager or email to manage PI? 3.

What problems have you experienced with managing your PI across these different devices

? Sub-questions: Do you have any difficulty in managing information on different devices? Do you have any problems with the file manager you use (if any)? Do you have any problems with other methods you use to manage your PI?

Acknowledgements. Acknowledgements are due to the NMMU/Telkom Centre of Excellence for funding this work.


Heiko Müller

Anastasia Kazakova

Martin Pielot
email: pielot@tid.es

Wilko Heuten

Susanne Boll

Ambient Timer -Unobtrusively Reminding Users of Upcoming Tasks with Ambient Light

Keywords: Ambient Light Display, Reminder, Interruptions, User Studies

Daily office work is often a mix of concentrated desktop work and scheduled meetings and appointments. However, constantly checking the clock and alarming popups interrupt the flow of creative work as they require the user's focused attention. We present Ambient Timer, an ambient light display designed to unobtrusively remind users of upcoming events. The light displaymounted around the monitor -is designed to slowly catch the user's attention and raise awareness for an upcoming event while not distracting her from the primary creative task such as writing a paper. Our experiment compared established reminder techniques such as checking the clock or using popups against Ambient Timer in two different designs. One of these designs produced a reminder in which the participants felt well informed on the progress of time and experienced a better "flow" of work than with traditional reminders.

Introduction

In many of today's office jobs, we are expected to fulfil tasks that require concentration, creativity, and time. Yet, in many professions the day of an office worker is highly fragmented [START_REF] Mark | No task left behind?: examining the nature of fragmented work[END_REF]. We arrive at 9 for a short briefing, have a meeting from 10-11, and leave at 12 to meet a colleague for lunch. Thus, we have to squeeze other work tasks into the free time slots and handle them one step at a time. In order to handle these tasks well and efficiently we need to focus our attention on them. Preferably we enter the state of flow, which means that we become fully immersed and focused on the task at hand [START_REF] Nakamura | Oxford Handbook of Positive Psychology, chapter Flow Theory and Research[END_REF].

Fig. 1. Ambient Timer

However, when fully concentrated, we are less likely to pay attention to upcoming meetings and appointments [START_REF] Block | Prospective and retrospective duration judgment: The role of information processing and memory[END_REF][START_REF] Casini | Multiple approaches to investigate the existence of an internal clock using attentional resources[END_REF]. We have observed two strategies to approach this problem: First, people that use electronic calendars have their devices create an alarm once the next meeting approaches [START_REF] Czerwinski | A diary study of task switching and interruptions[END_REF]. This, however, can disrupt suddenly and unpleasantly and leave workers with unfinished tasks, and a mental state that is not ready to focus on the new topic of the upcoming meeting [START_REF] Adamczyk | If not now, when?: the effects of interruption at dfferent moments within task execution[END_REF]. Second, many people keep watching the clock if a meeting is approaching soon. In this case, however, constantly switching between the primary task and watching the clock may be preventing the worker from focussing on the task at hand. In other cases, workers forget to check the time regularly and consequently do not show up in time for meetings.

What is missing is a solution that conveys the remaining time until the next meeting to workers, which allows them to focus on their primary task and enter a state of flow at the same time. Instead of sudden interruptions in form of alarms, we need a cue that gradually increases its saliency, moving slowly from subconscious into conscious perception, so that once the meeting arrives; workers have brought their primary task to a stable state and are ready to focus on the new topics.

We propose the concept of an Ambient Timer, which presents the time remaining for the current tasks in a way that slowly shifts from ambient to focal attention. As information display modality, we investigate the use of ambient light, which gradually increases obtrusiveness as the time for the current task runs out (Fig. 1). We envision the following usage scenario:

Alice is working on a report for the head of her department. At the same time, there is a meeting scheduled in thirty minutes, which she has to attend. The Ambient Timer is already emitting light in a low-attention state, so Alice feels confident that she will be reminded of the meeting. A few minutes before the meeting, the status of the ambient light display has changed to a more salient, intense output. While she is still working on her report, she slowly becomes aware of the nearing deadline and starts finishing the paragraph she is currently working on. One minute before the meeting the light has become so salient that it is hard to ignore. Alice stores the document on the server, puts her computer into sleep mode, and arrives at the meeting on time.

In this paper, we investigate how to gradually increase the saliency of an ambient light display, so that it slowly catches the attention of a person that is focusing on another task. We report from a study in which we compared the Ambient Timer to keeping track of time with a clock and to using a popup alarm in a typical office task. The results provide evidence that Ambient Timer gives people confidence in being able to see the progress of time, make them experience fewer interruptions, and make it subjectively easier for them to enter the state of flow.

Related Work

Ambient information displays received greater attention ever since Weiser introduced his work on "calm technology". He pointed out that calm technology engages and switches back and forth between periphery and centre of attention [START_REF] Weiser | Designing calm technology[END_REF]. Ishii et al. provided an insight into numerous possibilities for ambient displays in a work environment when creating their "ambientROOM" [START_REF] Ishii | ambientroom: Integrating ambient media with architectural space[END_REF]. Pousman and Stasko elaborated numerous definitions of ambient displays [START_REF] Pousman | A taxonomy of ambient information systems: Four patterns of design[END_REF]. In our understanding ambient information displays -such as the Ambient Timer -provide information which is important but not critical. They make a user aware of the information but do not require her to focus on the information display. "Human interruption", is defined as "the process of coordinating abrupt changes in people's activities" [START_REF] Mcfarlane | The scope and importance of human interruption in human-computer interaction design[END_REF]. Interruptions may have internal and external sources. An internal interruption may occur when e.g. throughout the process of writing a scientific paper new demand for literature arises. Thus the person will interrupt her work in order to find the required books. Examples for external interruptions are notification systems. McCrickard and Chewar describe notification systems as "interfaces specifically designed to support user access to additional digital information from sources secondary to current activities" [START_REF] Mccrickard | Attuning notification design to user goals and attention costs[END_REF]. While notification systems may often be distracting, this behaviour is usually tolerated by users [START_REF] Mccrickard | A model for notification systems evaluation assessing user goals for multitasking activity[END_REF]. Fogarty et al. report on the development of a sensor-based system to better automatically predict interruptability of human users [START_REF] Fogarty | Predicting human interruptibility with sensors[END_REF]. Ambient Timer aims to notify its users on the progression of time without distracting them from their primary task.

In their work, Matthews et al. define multiple attention levels: inattention, divided attention and focused attention [START_REF] Matthews | A toolkit for managing user attention in peripheral displays[END_REF]. Inattention defines a state, in which information is not consciously observed, while divided attention means that information is consciously perceived but does not require the fully focused attention of the user yet. The existing reminding techniques clock and popup alarm both require focused attention, as one would either have to read and understand the digits or hands of the clock, or close the popup window in order to return to the task at hand. We aim to have the Ambient Timer operate along inattention and divided attention transitioning from the first to the latter as time progresses. The orienting reflex as described by Sokolov [START_REF] Sokolov | Higher nervous functions: The orienting reflex[END_REF] poses limitations on the possible design solutions. Müller et al. report on a study exploring the design space of an ambient reminding system [START_REF] Müller | Unobtrusively reminding users of upcoming tasks with ambient light: Ambient timer[END_REF].

Mankoff et al. report an ambient system, informing users on the approach of local busses at a faculty building [START_REF] Mankoff | Heuristic evaluation of ambient displays[END_REF]. While displaying information on an upcoming event (the arrival of the bus) the reported system does not increase obtrusiveness to make users aware of when the bus is near.

Dragicevic and Huot introduced the idea of continuously displaying the time until an event using an analogue clock metaphor on the computer screen [START_REF] Dragicevic | Spiraclock: a continuous and non-intrusive display for upcoming events[END_REF]. This design aims at displaying information on time in an unobtrusive way. However, the information is displayed onscreen and not in the periphery.

Meyer et al. created a system for reminding elderly users of appointments and household events, utilising ambient light [START_REF] Meyer | Multimodal presentation of ambient reminders for older adults[END_REF]. Their system however is more of an "ambient popup alarm", as it gives no information on the progression of time nor on the time remaining until the appointment starts.

Vastenburg et al. reported their work on the acceptability of notifications in home situations [START_REF] Vastenburg | Considerate home notification systems: A user study of acceptability of notifications in a living-room laboratory[END_REF]. They found a correlation between user acceptability and intrusiveness and importance of the displayed message.

The above mentioned systems all address various aspects of ambient displays and conveying temporal information. However they do not address issues of gradual change in importance of temporal information and the need to notify the user on these changes without disrupting her.

On displaying information with increasing urgency in the periphery Birnholtz et al. report on a projected peripheral vision display [START_REF] Birnholtz | Awareness beyond the desktop: exploring attention and distraction with a projected peripheralvision display[END_REF]. Their results indicate that peripheral vision can be used to direct the user's attention. However, this system does not utilize an ambient light display, but rather projects graphical information.

What is missing is evidence that ambient light interfaces placed in the periphery allow to gradually shift the user's attention from inattention to focussed attention, without becoming disruptive.

In the following we report our experiment. We begin with a description of the apparatus.

Ambient Timer

As Ambient Timer we envision an ambient light display that notifies users unobtrusively of the progression of time in order to know when to finish the current task to be ready in time for the next appointment. Ambient Timer illuminates the periphery of a monitor, on which a user focuses her visual attention when working on the computer. Focal and peripheral vision may be regarded as two separate perception channels [START_REF] Horrey | Modeling drivers visual attention allocation while interacting with in-vehicle technologies[END_REF]. As peripheral vision is more sensitive closer to the foveal point [START_REF] Mckee | The detection of motion in the peripheral visual field[END_REF], we decided to place our ambient light display as close to the monitor as possible (Fig. 2). Placing the information in the periphery will allow the user keeping all monitor real estate for information that might not be suitable for display in the periphery.

To gradually grab the user's attention along the attention levels defined by Matthews et al. [START_REF] Matthews | A toolkit for managing user attention in peripheral displays[END_REF], the output of the Ambient Timer needs to gradually become more salient. In order to increase the saliency of the display to gain attention over time two forms of transition appear to be feasible: First, a sine wave change where the display alternates back and forth between two states with increasingly faster cycles. Second, we use an exponential change from the initial to the final state. Other forms of transition were ruled out after studying the related literature, e.g. linear change, which may not provide enough increased obtrusiveness due to human deficiencies in noticing slow changes [START_REF] Rensink | Change detection[END_REF], or cubic or saw tooth changes between initial and target state due to excessive obtrusiveness [START_REF] Sokolov | Higher nervous functions: The orienting reflex[END_REF].

Müller et al. [START_REF] Müller | Unobtrusively reminding users of upcoming tasks with ambient light: Ambient timer[END_REF] explored the design space for displaying gradual changes with ambient light. Their results suggest that colour changes may be superior to change in brightness or saturation. While a sinusoid change may not require a sharp contrast from start to target colour, exponential changes -which appear to be more unobtrusive by design -require a sharp contrast of complementary colours such as green to red. As reported, the traffic light analogy was found helpful by participants. With regard to these results, we chose to introduce a sinusoid colour change with increasing frequency from green to orange as well as an exponential change from green to red as conditions for Ambient Timer, thus evaluating the patterns from each category that achieved best results overall against state-of-the-art reminding techniques.

Fig. 2. Concept of Ambient Timer

Our apparatus is made of uniformly controlled LED-stripes which were fixed to a three-sided frame that had the same width and height as a 22 inch monitor used for our studies (Fig. 3). This frame is mounted on the back of the monitor (Fig. 4). We placed frame and monitor on a desk close to a matt white wall. The gap between monitor and wall was about ten centimetres. This provided us with a surface to reflect the light emitted by the LEDs and illuminate the immediate periphery of the monitor. While the user focuses her view on the monitor, she can perceive the ambient light display in her peripheral vision.

Fig. 3. LED-Frame

Methodology

In our experiment, we investigated if the Ambient Timer allows workers to work more concentrated and efficiently than when using state of the art reminders. Our general approach was to expose participants to a demanding primary task and evaluate the effectiveness of the Ambient Timer as reminding technique compared to state of the art baselines. As a primary task, we asked participants to copy (type) given texts and correct mistakes we placed in the original documents. Copying and correcting texts is a task requiring good concentration. Thus the impact of interruptions would be serious [START_REF] Gillie | What makes interruptions disruptive? a study of length, similarity, and complexity[END_REF].

As secondary task, we asked the participants to be aware of the time and finish the primary task within ten minutes. We defined finishing as finalizing to copy and correct a full sentence once the participants thought that available time was running out.

Fig. 4. LED-Frame mounted on the backside of the monitor

Participants were instructed to inform the experimenter, when they thought that they had finished the primary task. Participants were discouraged from exceeding the time limit (overshoot), i.e. to take longer than ten minutes. If participants missed the end of the time period by more than 30 seconds a popup window informed them of the end of the trial. For staying aware about the remaining time, we experimentally compared two implementations of the Ambient Timer with using a clock, i.e. participants had to monitor the progress of time on a system clock with digits, and pop-ups, i.e. the only information given was a pop-up that was shown two minutes before the time expired. The two implementations of Ambient Timer were:

AT Expo: remaining time was conveyed via an exponential colour change from green to red.

AT Sinus: remaining time was conveyed via a sinusoid colour change between green and orange with increasingly faster cycles.

Our hypotheses were that: H1: With the Ambient Timer, participants will be or feel less interrupted than with the clock. H2: Participants will find/correct more and make less new mistakes when using the Ambient Timer. H3: Participants feel confident and well informed on the progression of time when using Ambient Timer. H4: Participants will find Ambient Timer as the favourable reminding technique.

Design

Type of Reminder, i.e. the way that participants were informed about the time that remained to complete the current task, served as independent variable. We compared four different techniques:  In the Popup condition, the participants had no information about the remaining time. Instead a popup window appeared to inform them about the end of the task two minutes before the time expired. This condition reflects the common strategy of not checking the clock and only relying on popups by the calendar system to be reminded of appointments.  In the Clock condition, we showed the system clock in the task bar at the bottom of the screen. The clock showed the current time with hours and minutes. No seconds were shown. By knowing when the task had to finish, the participants could calculate how much time is left. This condition reflects the other common strategy of keeping an eye on the clock when a meeting is approaching.  In the AT Expo condition, the Ambient Timer was used to convey the remaining time via an exponential colour change from green to red.  In the AT Sinus condition, the Ambient Timer was used to convey the remaining time via a sinusoid colour change between green and orange. With this condition, we aimed at testing a more obtrusive pattern, in case that the exponential change proves to be too unobtrusive when the user focusses on the primary task.

Except for in the Clock condition, no clock was available to the participants. During the experiment, the order of these conditions was counter-balanced to cancel out sequence effects. In order to assess the unobtrusiveness of these designs, and answer the hypotheses, we logged the following measures as dependent variables:

 Interruptions: The number of interruptions, i.e. any occurrence of a pause between keystrokes of more than one second.  Keystrokes: the total number of keystrokes per task. We measured keystrokes to gain insights into how well participants were able to focus on the copying task in the various conditions.  Keystroke Time: the average time between two keystrokes. This measure was taken to gain insight into the ratio of total keystrokes and interruptions. As not all participants stopped exactly at the ten minute mark and as the obtrusiveness of the displays was not evenly distributed across time we did not simply normalize our measures.  Corrected Mistakes: the number of grammar and spelling mistakes corrected per task. We measured Corrected Mistakes to quantify how concentrated our participants can work with the compared reminding techniques.  Newly Introduced Mistakes: the number of grammar and spelling mistakes that are newly introduced by the participant per task. Newly Introduced Mistakes was also measured to estimate the participants' level of concentration and flow.  Overshoots: a Boolean value indicating whether the participant did not finish the task on time. If the participant continued to work on the task for more than 30 sec-onds after the time ran out, we interrupted the task and counted this task as an over shoot. With this measure, we aimed at quantifying how well the different reminders helped the participants to stay aware of the remaining time.

In addition, for each of the conditions, we collected the participants' agreement (5point Likert scale) to the following statements:

Apparatus

The texts to correct were taken from a collection of dictations for teachers working with tenth graders [START_REF] Sczyrba | 100 Diktate f• ur das 8. -10. Schuljahr: mit Übungen zur Rechtschreibung und Grammatik[END_REF][START_REF] Fehlbusch | [END_REF][START_REF] Sämann | Diktate wie in der Schule: Deutsch, 5. -10. Schuljahr[END_REF]. Each dictation had a special focus on certain words which we used as a guideline for placing mistakes into the text. For the copy and correct task, the screen was divided into two parallel text-fields, one containing the text, one used to copy the text into.

As work place, we used a standard desktop computer running Windows 7 with a 22-inch monitor on a standard working table. As shown in Fig. 5, the participants were provided with a text field to copy the text into. In the Clock Condition, we showed the current time, as shown in Fig. 6.

Fig. 6. On-screen system clock

We conducted our studies in a room with controlled light setting thus eliminating possible effects of changing surrounding light [START_REF] Ferwerda | A model of visual adaptation for realistic image synthesis[END_REF]. We kept the light level constant at 420 lux at the desktop which is in compliance with rules on office workspace settings.

For tracking interruptions, we used a key logger script that measured the time between individual keystrokes.

Participants

12 participants (4 female, 8 male) aged 17-45 (M = 28.3, SD = 8.8) took part in the experiment. None of the participants reported a case of colour blindness. All participants were experienced in writing texts on computers. All participants rated their typing speed between fast and medium, two of them used 10-finger-typing.

Asked about their method of reminding themselves of appointments, participants either used a calendar with alarms on their computer [START_REF] Dragicevic | Spiraclock: a continuous and non-intrusive display for upcoming events[END_REF] and/or on their phone (5) as well as regularly checked the clock (4). When using reminders, the lead time to appointments was stated to be any time from five to 60 minutes, or even one to two days in advance for full day events. All but one participant answered that they "sometimes" to "never" missed appointments. One participant said that missing appointments was a common occurrence. Participants received no compensation for their participation.

Procedure

Before the start of the experiment, participants were introduced to the scope of the study and familiarized with both light designs of the Ambient Timer. We then conducted four trials per participant, exposing them to the four conditions in randomized order.

After each trial, participants were asked to rate their agreement to the five statements regarding the used reminding technique. Upon completion of all four trials, we collected the participants' impressions in an open interview.

Results

Objective Measures

Figure 7 shows the descriptive statistical summary for the objective measures. We used repeated measures one-way ANOVA and Tukey HSD to test for significant effects.

Fig. 7. Descriptive summary of objective measures (Bars show mean, error bars indicate standard deviation)

There was a significant effect on Overshoots (F(3, 44) = 9.0, p < .001). The number of Overshoots was significantly higher in the AT Sinus condition, compared to the Popup (p < .001), Clock (p < .001), and AT Expo (p < .001) conditions. Thus, participants had more difficulties to finish their tasks on time in the AT Sinus condition; participants did not finish their tasks on time as often as in the other tasks.

There were no significant effects on Interruptions (F(3,44) = 0.29, p = .83), Keystrokes (F(3,44) = .04, p = .99), Keystroke Time (F(3,44) = .09, p = .97), Corrected Mistakes (F(3,44) = 2.03, p = .12), and Newly Introduced Mistakes (F(3,44) = .47, p = .7). Hence, we cannot make any assumptions about the effect of Type of Reminder on the remaining dependent measures.

Subjective Measures

Fig. 8 shows the Median ratings of the participants' level of agreement with the six Likert-scale statements per condition. Assuming normally-distributed, interval scores, we analysed the data for significant effects by using repeated measures one-way ANOVA and post-hoc Tukey HSD tests.

Fig. 8. Median level of agreement with the six statements per condition

There was a significant effect on the agreement to the statement I think this technique is good (F(3, 44) = 4.5, p < .01). The level of agreement in the AT Expo condition was significantly higher than in the Popup (p < .05) and in the Clock (p < .05) conditions. Thus, participants found AT Expo to be a better reminding technique than Popup and Clock.

There was a significant effect on the agreement to the statement I felt distracted by the system (F(3, 44) = 4.8, p < .01). The level of agreement in the AT Expo condition was significantly lower than in the Popup (p < .05), Clock (p < .05), and AT Sinus (p = .06) conditions. Thus, participants found AT Expo to be less distracting than the other reminding techniques.

There was a significant effect on the agreement to the statement It was easy to monitor the progression of time (F(3, 44) = 8.7, p < .001). The level of agreement in the Clock condition was significantly higher than in the Popup (p < .01) and AT Sinus (p < .01) conditions. Likewise, the level of agreement in the AT Expo condition was significantly higher than in the Popup (p < .001) and AT Sinus (p < .001) conditions. Thus, in the Clock and AT Expo conditions, participants found it easier to monitor the progress of time than in the Popup and AT Sinus conditions.

There was a significant effect on the agreement to the statement I felt sure about noticing the progression of time (F(3, 44) = 14.0, p < .001). The results are analogue to the previous statement. The level of agreement in the Clock condition was significantly higher than in the Popup (p < .001) and AT Sinus (p < .001) conditions. Likewise, the level of agreement in the AT Expo condition was significantly higher than in the Popup (p < .001) and AT Sinus (p < .001) conditions. Thus, in the Clock and AT Expo conditions, participants were more confident that they would notice the progress of time than in the Popup and AT Sinus conditions.

There was a significant effect on the agreement to the statement I was able to complete the task in time (F(3, 44) = 7.3, p < .001). The level of agreement in the AT Expo condition was significantly higher than in the Popup (p < .05) and AT Sinus (p < .05) conditions. Thus, participants found it easier to complete the task in time in the AT Expo condition compared to the Popup and the AT Sinus conditions.

We could not find a significant effect on the agreement to the statement I entered the state of flow (F(3, 44) = 2.6, p = .06, marginally significant).

In summary, the clock and the Ambient Timer in the AT Expo condition were found to make it easy to monitor the progress of time and finish the task in time. In addition, the Ambient Timer in the AT Expo condition was found to be the better reminding technique and was rated to be least distracting.

Comments and Observations

For Clock, six participants answered that as keeping an eye on the clock was very common, it should not pose a problem. They felt it was reliable and that they were "in control". On the other hand ten participants answered when asked what had distracted them that switching focus from text to clock and back posed some problems in finding the correct line in the text again. Concerning Popup, five participants were unhappy with the way the popup interrupted their work. Three participants commented that they liked how the system was hidden in the background until it popped up and that they could work relaxed until then.

On AT Expo, one participant said it was difficult to see the end of time, while another argued that it was like a clock only better. The calm exponential change was well accepted.

AT Sinus was found to be obtrusive by six participants. They felt unsure on how much time had already passed and said that they were somewhat distracted by the constant change of colours. While two participants said that the colour change was too subtle to notice without looking, one participant answered that he liked the subtle changes best. Three participants mentioned that they might be able to get used to AT Sinus but that it needed more time to familiarize.

Ten participants said that they can imagine using the Ambient Timer, while two answered that they would not want to use it. Of the ten positive answers, one participant would use the Ambient Timer stand-alone, while the others preferred a combination of techniques (+ Popup (6), + Clock (3)) for better control of when the time ran out.

Concerning acceptability of an ambient light display placed at the user's desks 11 participants considered using the Ambient Timer in a work environment as being unproblematic. Out of the positive answers, some participants argued that the system could signal other colleagues that the user is about to leave for a and that a discussion should be postponed to a later time, thus adding extra value to the information of an upcoming task. However, when engaged in group meetings or talks with customers or other outsiders, participants would like an option to temporarily disable the system as they felt the use of such a system inappropriate in these situations. Only one participant could imagine using Ambient Timer solely in a private setting.

Asked about the display time of Ambient Timer, most participants would prefer a lead time of 10-15 minutes to be able to bring their current work into a stable state before having to leave for the appointment.

We asked participants if they could think of other light patterns or colours to use in Ambient Timer. Five participants liked the AT Expo the way it was, especially as they liked the green = "go", red = "stop" traffic light analogy. A couple users suggested using blue as a starting colour, arguing that blue was a calming colour. Two participants suggested an exponential pattern with a flashing part at the end of the time period so that it would be easier to see.

Discussion

The experiment compared two designs of Ambient Timer, one with an exponential change of colour from green to red (AT Expo), and one with a sinusoidal change between green and orange with increasingly faster cycles (AT Sinus), a clock, and pop ups as means to monitor the remaining time. Our results show that participants experience fewer interruptions when using Ambient Timer with an exponential change from green to red, compared to all other reminder techniques in our experiment. Their average typing speed was faster when in this condition. Participants ranked this design best, felt most confident using it and preferred it over all other techniques. Discussing results in relation to our hypotheses, we find that we have a split between the two Ambient Timer designs. While the exponential change from green to red performed very well, users experienced no benefits over state-of-the-art reminding techniques from the sinusoid change between green and orange. On the other hand it is worth to mention, that the sinusoid design was by no means a dropout.

H1: Participants will experience fewer interruptions when using the Ambient Timer No significant effects could be found in a one-way ANOVA test of key-logging data to support this hypothesis. However, our participants' answers to the question of being in the "flow" received marginally significant better results for the exponential Ambi-ent Timer design than when participants were in the Clock condition. Ambient Timer's idea of reminding users without interrupting them works well in the exponential Ambient Timer design.

H2: Participants will make fewer mistakes when using the Ambient Timer Even though participants found more mistakes we had prepared in the texts when using both Ambient Timer designs, we could not reveal any statistical significance for these findings from the key logging data. Hence, there is no evidence to support this hypothesis.

H3: Participants feel confident and well informed on the progression of time when using Ambient Timer This hypothesis can be confirmed for the Ambient Timer with the exponential design and falsified for Ambient Timer in the sinusoid design. The exponential design scored roughly the same results as when participants used the clock, while state-of-the-art reminding technique Popup and the Ambient Timer with the sinusoid design scored results worse than average. The data revealed significantly better results for the exponential Ambient Timer design compared to state-of-the-art technique Popup and the sinusoid Ambient Timer design, as well as significantly better results for Clock compared to Popup and the Ambient Timer with the sinusoid design. We have no statistical evidence that the Ambient Timer with the exponential design performed better than Clock. Considering the significantly better results of exponential Ambient Timer design over Clock and Popup concerning the statement "This pattern is good" we conclude that Ambient Timer when in the exponential design makes a good alternative to state-of-the-art reminding techniques.

H4: Participants will find Ambient Timer as the favourable reminding technique This can be verified for Ambient Timer in the exponential design and falsified for the sinusoid Ambient Timer design. The exponential Ambient Timer design ranked best together with Clock, while the sinusoid design ranked last.

Overall, H1 (less interruptions) was supported for the exponential Ambient Timer design and Clock, H2 (less mistakes) was not supported, and H3 (well informed) and H4 (favourable) were supported for Ambient Timer in the exponential design but not for the sinusoid design.

We have recorded split results suggesting that the benefits of using ambient light for reminding users of upcoming events depends on how the design increases its saliency to grab the user's attention. In our experiment, the exponential Ambient Timer design receives better scores on all questions we have asked our participants and is ranked best in the order of participants' preference. Participants' feedback in our questionnaires and interviews suggest that they like the way Ambient Timer in the exponential design keeps them updated on the time progress without them having to take their eyes off the primary task or being interrupted unexpectedly. With the exponential Ambient Timer design we have introduced a true alternative to the state-of-the-art reminding techniques Clock and Popup.

Concerning acceptability, the majority of participants had no concerns about the visibility of the system in an office environment. They saw benefits such as coworkers being more aware of the individual schedules. However, some would prefer to "mute" the system in group-work situations and when meeting with customers.

One of the limitations of our experiment is the type of setting. Evaluating ambient displays in a lab condition is always difficult, as the expected benefit of blending into the environment can hardly be achieved in a lab setting [START_REF] Hazlewood | Issues in evaluating ambient displays in the wild: two case studies[END_REF]. When using the Ambient Timer, participants were using a system that was already "on", which it would not normally be in a regular office setting. Therefore we cannot make any statements on how users will react to a "warm-up/turn-on"-phase. While we aimed at creating a challenging task that could be solved by the participants, we cannot simulate tasks that are truly relevant for our participants, which would then have enabled them even further to experience flow and immerse themselves in the tasks.

Conclusion

We presented Ambient Timer, a way of unobtrusively reminding users of upcoming events and appointments using ambient light. In an experiment, we compared the exponential change of colour from green to red, a sinusoidal change between green and orange with increasingly faster cycles, a clock, and pop ups as means to monitor the remaining time. The results show that ambient light can successfully convey remaining time. In particular, the exponential change from green to red was preferred over all other approaches. The participants found it to be a non-distracting way of monitoring the remaining time, in order to know when to wrap up the primary task.

The main contribution of the work is to provide evidence that ambient light displays are a good solution for extending the information space in an office environment by displaying information outside the user's monitor. Ambient light displays can help adding important information (such as reminders on upcoming tasks) without adding clutter or interruptions to the user's workflow by requiring focused vision. In a work environment that is increasingly exposed to interruptions, such approaches may help information workers to structure their days and focus on their primary tasks.

Future directions for this work will be a long-term test in an office environment evaluating ambient light "in the wild", giving participants a chance to evaluate the system against their usually used reminder technique over the course of a week. Participants will design their "own" light patterns, thus avoiding possible pitfalls such as colour vision deficiencies. This would give insights into how it blends into the periphery and becomes noticeable when appointments are due. Further we are reworking the prototype to make it more flexible in use by adding a semi-transparent cover. This will allow users, who do not have their computer monitor against a wall, to be able to see the light display.

Another possibility for further research is on novel light patterns for, using both uniform illumination of all LEDs as well as patterns controlling LEDs individually thus creating opportunities for evaluating "moving" patterns as well.



  I think this technique is good.  I felt distracted by the system.  It was easy to monitor the progression of time.  I felt sure about noticing the progression of time.  I was able to complete the task in time.  I entered the state of flow.

Fig. 5 .

 5 Fig. 5. Screen to copy and correct text

Acknowledgments

We would like to thank our colleagues as well as and all participants in our pilot study and the experiment for the valuable feedback on our design and all the time they invested.