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Mental workload in multi-device personal information management

Mental Workload in Multi-Device
Personal Information Management
Manas Tungare
sub-tasks and redesign or optimize the user experience Dept. of Computer Science, Virginia Tech.
selectively. In addition, we believe that mental workload shows promise as a cross-tool, cross-task method of evaluating PIM tools, services and strategies, thus fulfilling a need expressed by several researchers Manuel A. Pérez-Quiñones
in the area of personal information management. In Dept. of Computer Science, Virginia Tech.
this paper, we describe our ongoing experiment of measuring mental workload (via physiological as well as subjective measures) and its implications for users, designers and researchers in PIM.
Personal Information Management, Mental Workload, Knowledge workers increasingly use multiple devices such as desktop computers, laptops, cell phones, and PDAs for personal information management (PIM) ACM Classification Keywords
tasks. The use of several of these devices together H.5.2 Information Interfaces and Presentation: User creates higher task difficulty for users than when used individually (as reported in a recent survey we conducted). Prompted by this, we are conducting an Introduction & Motivation
experiment to study mental workload in multi-device As we amass vast quantities of personal information, scenarios. While mental workload has been shown to managing it has become an increasingly complex decrease at sub-task boundaries, it has not been endeavor. The emergence of multiple information studied if this still holds for sub-tasks performed on devices and services such as desktops, laptops, cell different devices. We hypothesize that the level of phones, PDAs and cloud computing adds a level of support provided by the system for task migration complexity beyond simply the use of a single computer. affects mental workload. Mental workload In traditional single terminal computer systems, the measurements can enable designers to isolate critical majority of a user’s attentional and cognitive resources are focused on the terminal while performing a specific task. However, in an environment where multiple devices require intermittent attention and present Copyright is held by the author/owner(s).
useful information at unexpected times, the user is CHI 2009, April 4 – 9, 2009, Boston, MA, USA subjected to different mental workload.
In an earlier study we conducted [15], users another [13]. A related goal of our research is to consistently reported difficulties in performing examine if the increase in mental workload at the point information tasks with multiple devices, especially when of transition is correlated with the level of system transitioning between/among devices. From the support available for the sub-task of transitioning. I.e., responses we received, we observed (from a content if the system incorporates full support for task analysis of free-form responses) that users’ adoption of migration, we hypothesize that mental workload will be various technological alternatives is guided by an innate less than in case of another system where such support sense of certain specific factors. We noted that several of these factors constitute mental workload, e.g. frustration level, temporal demand, and mental effort. In addition, there has been no standard way to In systems where users lacked the freedom of choice, compare the effectiveness of tools, services, and they turned to solving problems by adopting techniques developed independently at different workarounds motivated by one or more of these research labs. Kelly [9] notes the methodological difficulties in studying PIM because of its highly personal nature, leading to challenges in developing a It has been shown that an operator’s task performance set of reference tasks or cross-tool cross-task metrics. is inversely correlated with high levels of mental In several other task domains, workload assessments workload [12]. Thus, we set out to explore if mental such as NASA TLX [6] have been administered instead workload estimates could be used to compare task of direct measurement of task performance metrics for difficulty in PIM tasks. Prior work in mental workload several reasons: chief among them is that subjective measurement has established that physiological workload assessments require less effort and measures such as changes in pupillary diameter instrumentation of the task, and are easier to (known as Task-Evoked Pupillary Response [3]) can be administer. If mental workload in PIM tasks can be used to estimate mental workload. Such continuous shown to be inversely correlated with task performance measures of mental workload can help locate sub-tasks (as has already been shown in several other domains of high task difficulty. Iqbal et al. [8] demonstrated that [12, 2, 5]), such a measure can be used to compare within a single task, mental workload decreases at sub- the effectiveness of these tools across varying tasks. task boundaries. A fundamental goal of our research is Thus, a tertiary goal of our research is to examine to examine if their finding still applies when the latter whether mental workload estimates captured using the sub-task is performed on a different device than the NASA TLX scale can serve as a predictor of task former. Our contrary hypothesis is that mental workload performance for personal information management rises just before the moment of transition, and returns to its normal level a short duration after the transition is complete.
Related Prior Work
Mental workload is an important, practically relevant,
Systems differ in the level of support they provide for and measurable entity [6]. The NASA Task Load Index pausing a task on one device, and resuming it on (NASA TLX) [6] is a multi-dimensional subjective workload assessment technique that has been applied Results from Preliminary Studies
in studies of airline cockpits [2], navigation [14], and in Experimental tasks for the current study were chosen the medical field [5]. It combines information about from among the most common representative tasks specific sources of workload weighted by their identified in an exploratory survey study [15] and relevance, thus reducing the influence of those are another ethnographic investigation [16] (reported experimentally irrelevant, and emphasizing the contributions of others that are experimentally relevant. This reduces between-subject variability for File management across multiple machines stood out as the measure as compared to other subjective scales.
the most reported problematic task. 12 out of 79 survey users said that they encountered difficulties Physiological measures such as changes in pupillary while syncing data between multiple machines, 11 diameter (known as Task-Evoked Pupillary Response) reported unexpected deletion of their data while have been shown to be responsive to changes in copying across machines, and 6 reported having mental workload [3] and used as a physiological trouble with managing conflicting versions of files that measure of mental workload in several studies [7, 1]. were copied manually. Based on these findings, our first Within a single task, mental workload decreases at sub- experimental task involves managing files across a task boundaries [8]. Such continuous measures of desktop and a laptop, with and without support for mental workload can help locate sub-tasks of high task From the ethnographic investigation of calendar use As the problem of information overload has worsened [16], we found that paper calendars were actively used over the years, human attentional resources have by a majority of interviewees despite the widespread stayed constant [11]. The issue of information prevalence of electronic calendars (corroborating the fragmentation across multiple devices (the condition of findings reported in previous studies). 35% of having a user’s data in different formats, distributed participants reported printing their electronic calendar across multiple locations, manipulated by different for offline use. Based on this, our second experimental applications, and residing in a generally disconnected task is calendar management, and involves managing manner [4]) threatens the effectiveness of users as schedules using an online calendar and paper An understanding of mental workload in PIM tasks is From the survey, we also found that several devices are not only expected to lead to a better understanding of often used in groups, e.g. laptops and cell phones why a particular tool causes high frustration or mental (reported by 52 participants), and integrated multi- demand in users, but also can be used to isolate critical function portable devices such as Palm Treos, sub-tasks and for comparing different tools against one Blackberries and Apple iPhones have begun to replace single-function devices for communication (e.g. email and IM). Given this, we picked contact management as Physiological Measure: Task-Evoked Pupillary Response Subtle yet measurable changes in pupil diameter have been associated with cognitive workload and referred to Methodology and Experimental Setup
as the Task-Evoked Pupillary Response (TEPR) [3]. This mixed-method study consists of an experiment, Participants wear a head-mounted eye-tracker preceded by a questionnaire, and followed by an throughout the duration of the experiment that permits interview. Participants are invited to perform three free head movement while still tracking eye gaze and tasks in two sessions each to cover three different pupil diameter with reasonable accuracy. Pupil diameter information collections: (1) files, (2) calendars and (3) (adjusted and normalized for other factors) has been contacts. Each task is performed in two different ways shown to be a good predictor of cognitive workload [7, in the two sessions; the difference in treatments is the 10]. This technique provides a continuous measure of level of system support for task migration. E.g. for the files task, users perform the task using either USB drives (low level of task migration support) or network Subjective Measure: NASA Task Load Index (TLX) After every task, participants are requested to record their subjective assessment of mental workload via the Each task consists of a set of instructions (between 15 NASA TLX questionnaire. This offers a task-level and 20 each) to locate, read, modify, and save estimate of mental workload that is useful as a cross- information. In each task, a few instructions include questions directly related to the information at hand. The experimenter collects the answers and uses them as a metric of task performance (details later). Direct task-related metrics such as time taken, errors Interspersed within these are instructions to switch encountered, information overwritten or not correctly devices, e.g. one of the instructions for the file propagated across devices, and incorrect information management task reads: “Complete all your work on used are being measured and used to determine if high the desktop, and prepare to travel to a different office mental workload correlates negatively with task performance. These are measured after the participant session has concluded, by (1) analyzing eye-gaze The second session is conducted (at least) two weeks video, (2) automatic instruction-level time-tracking in after the first session, in order to minimize the learning the system that displays task instructions, (3) effects caused by the first session. In this within- analyzing the end products of interaction, e.g. saved subjects design, ordering effects are minimized by files, modified calendars and (4) answers to questions randomizing the order of treatments between sessions, posed at the end of individual instructions.
as well as the ordering of tasks within each session.
As of January 2009, pilot studies have been conducted Mental Workload is measured via two different ways: with 8 participants and a few initial participants have been recruited and scheduled for the first session.
Expected Results & Design Implications
mental workload is found to be unexpectedly high Designers of PIM products and services strive to create during certain task sequences in a higher-level task.
solutions that make it easier for users to get their tasks done. However, an evaluation of the effectiveness of these tools poses tricky challenges. Kelly [9] notes that In this paper, we describe a study in progress that “research and theory concerning PIM behavior and tools seeks to understand the changes in mental workload have been stymied, since it is difficult to accumulate, during personal information management tasks compare, and integrate results across studies” and performed using multiple information devices. We expresses an urgent need for “developing evaluation extend prior work in mental workload measurement to methods and metrics that produce valid, generalizable, the domain of PIM, and seek to examine its correlation sharable knowledge about how users go about the PIM with task performance. Mental workload is measured activities and interactions in their daily lives.” via physiological as well as subjective measures, while task performance is measured using several task- We believe that the results of our experiment will specific metrics for three independent tasks (each of contribute to exactly such an endeavor. Mental which was selected based on the results of two prior workload already accounts for subjective factors such studies.) This study has important implications for PIM as frustration and mental demand, factors that users system designers who can then use mental workload have reported as important in influencing their choice measures as a cross-task, cross-tool method for of device/tool/strategy. If, further, mental workload can comparing the effectiveness of PIM tools and services be shown to be correlated with task performance, then developed independently of one another.
it has tremendous potential in being used for cross-tool evaluations and for comparing vastly different PIM Acknowledgments
methodologies with one another. If, as we expect, we We would like to thank Tonya L. Smith-Jackson for are able to find significant correlation among instigating some of the ideas behind this project. Steve physiological and subjective measures of mental Harrison, Edward A. Fox, Stephen Edwards and Pardha workload and task performance, designers will be able S. Pyla also provided important insights that led to the to evaluate their tools using non-intrusive low-overhead design of this study in its current form. We wish thank subjective workload assessment tests such as NASA our pilot participants as well as future participants for Not only will we be able to determine if a particular References
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