Abstract High-quality hospital care requires careful medication management. The infrastructure in place to avert errors in medication management involves formal work procedures, elaborate electronic systems, and, we argue, continual repair work. Repair is the work required to restore things to working order after a breakdown. In this study, we analyze the repair work performed by the healthcare professionals tasked with two electronically supported medication-management processes at hospitals in Norway: medication reconciliation and closed-loop medication management. On the basis of interviews and supplementary material, we find that the repair work involved in these two activities is collaborative, continuous, and critical. It is collaborative in that it is performed by physicians, pharmacists, and nurses and, thereby, neither assigned to a single person nor to a group of designated repairers. It is continuous because the repairs do not fix the causes of the breakdowns but merely restore the individual instance of medication management to working order. It is critical in the double sense that repair work is a requirement for quality medication management and that quality repair work is also a requirement. We discuss the implications of the repair work, including the consequences of variation in the achieved level of repairedness.

• Preference is in general associated with workload, task time, and error rate. • Workload is a stronger predictor of preference than performance is. • Task time is a stronger predictor of preference than error rate is. • Preference is occasionally dissociated from workload, task time, or error rate. • Experience level and safety criticality moderate the findings. A user's preference for one system over another is probably the most basic user experience (UX) measure, yet user studies often focus on performance and treat preference as supplementary. This meta-analysis of 144 studies shows that while users in general prefer systems with which they achieve lower task time and error rate, they more consistently and more strongly prefer systems that impose lower workload. In only 2 % of the studies a preferred system imposes significantly higher workload than a nonpreferred system. Across the studies, a stronger preference coincides with a larger difference in workload, task time, and error rate. This correlation is strongest for workload, lower for task time, and lowest for error rate. That is, workload is a stronger predictor of preference than performance is, even for the near exclusively utilitarian tasks covered by this meta-analysis. The implications of these findings include that workload should be more fully integrated in research on usability, UX, and design and that it is risky for practitioners to infer preference from performance, or vice versa.

Abstract In information infrastructures at hospitals, various stakeholders are responsible for specific information and communications technology (ICT) portfolios. Each portfolio represents a unique digital trajectory with a past, present, and future. This study investigated how stakeholders (in this study, software developers, ICT operations organizations, and users) collaborate to facilitate the convergence of different digital trajectories, thus contributing to the successful evolution of information infrastructures. Empirically, we focused on the preparatory work involved in implementing an app that would enable nurses to register and calculate National Early Warning Scores at Nordland Hospital in northern Norway. Specifically, we examined the collaboration between three stakeholders to align their respective ICT portfolios and prepare for the new solution. These stakeholders were the Finnish software developer Medanets, the Norwegian Electronic Health Record developer DIPS ASA, and the Northern Norway Regional Health Authority, which governed the regional health ICT infrastructure. These stakeholders governed three distinct portfolios that had been developed over many years and, in this sense, represented digital trajectories with a past, a present, and a possible future. This study is positioned within the computer-supported cooperative work field, and the analysis draws upon the theoretical concepts of information infrastructure and trajectories.

Artificial intelligence techniques, including machine learning (ML), have shown remarkable test results over the past decade but struggled with the transfer to practical application. The present study applies action research to investigate this last stage of a project to implement an ML algorithm for predicting no-shows at a Danish hospital. We approach the implementation of the no-show algorithm as an innovation process and identify 14 tactics that were employed to provide the innovation necessary at the implementation stage. The tactics span three analytic levels – organization, project, and practice – and alternate between efforts to train the algorithm and establish trust in its predictions. These efforts are interdependent, highly sociotechnical, and hence blur the boundary between technical development and organizational implementation. They also show the intricacies involved in innovating during ML implementation. Despite sustained support at the organization level, the implementation of the no-show algorithm at the practice level remained unsettled.

Abstract Robotic vacuum cleaners are a prime example of home automation and a rich source of information about how people experience it. On the basis of a 3-week diary study, this article compares householders’ user experience (UX) of robotic vacuum cleaners with their UX of three types of manual vacuum cleaner. The main finding is that robotic vacuum cleaners are inferior in use, yet transform vacuuming. While their inferiority is about their pragmatic qualities, their transformative power relates to their autonomy, agency and hedonic qualities. This contradictory UX involves that robotic vacuum cleaners perform worse or not at all on seven out of nine surfaces and, at the same time, appear to escalate cleanliness standards. The transformation of household chores such as vacuuming is ongoing and calls for further research on engineering and merging the pragmatic and hedonic aspects of UX.

In usability tests, the users are commonly asked to think aloud to let the evaluator listen in on their thoughts. Two variants of this procedure involve that the users either think aloud while using the tested product (concurrent thinking aloud, CTA) or after using it (retrospective thinking aloud, RTA). This study reviews the studies that compare CTA and RTA to investigate what is gained and lost by using one or the other variant in a usability test. A total of 29 studies, reporting from 42 comparisons of CTA and RTA, matched the inclusion criteria and were included in the meta-analyses. The main differences are that for CTA task time is longer, but total time shorter, whereas for RTA the users verbalize more explanations, problem formulations, and design recommendations. In addition, CTA users probably experience the evaluator’s presence as less disturbing than RTA users do.

Abstract Experimentation is the process of trying something out to discover what happens. It is a widespread information practice, yet often bypassed in information‐behavior research. This article argues that experimentation complements prior knowledge, documents, and people as an important fourth class of information sources. Relative to the other classes, the distinguishing characteristics of experimentation are that it is a personal—as opposed to interpersonal—source and that it provides “backtalk.” When the information seeker tries something out and then attends to the resulting situation, it is as though the materials of the situation talk back: They provide the information seeker with a situated and direct experience of the consequences of the tried‐out options. In this way, experimentation involves obtaining information by creating it. It also involves turning material and behavioral processes into information interactions. Thereby, information seeking by experimentation is important to practical information literacy and extends information‐behavior research with new insights on the interrelations between creating and seeking information.

When computers unexpectedly delay or thwart goal attainment, frustration ensues. The central studies of the extent, content, and impact of such frustration were done more than 15 years ago. We revisit this issue after computers have become more mature and computer use is more extensive. To this end, we had 234 crowdsourced participants log the frustrating episodes they experienced with their computers during one hour of computer use. The average time lost due to frustrating episodes was between 11% and 20% of the one-hour period. Though this is less time lost than in the earlier studies, frustration remains a common user experience. While shorter, the median level of frustration during the episodes was high (7 on a 9-point scale). The frustration level correlated with task importance and time lost but was unaffected by computer experience and largely unaffected by computer self-efficacy. In addition, participants indicated that 84% of the episodes had happened before, that 87% could happen again, and that they were unable to resolve 26% of the episodes. This high rate of recurrence and lack of control likely added to the frustration level. The episodes spanned various issues pertaining to performance (49%), usability (36%), and utility (16%).

Workload is an important explanatory variable in human–computer interaction and commonly measured with the Task Load Index (TLX). Thus, it is important to understand the qualities of TLX and its relations to other variables. By reviewing 384 papers that apply TLX, this study analyzes how differences in TLX and its six subscales are associated with one another and with differences in performance, user experience, and situational characteristics. Six findings stand out. First, the TLX subscales measure associated, but somewhat independent, dimensions of workload. Second, people compensate for demanding conditions by putting in more effort and, as a result, sometimes avoid a drop in performance. Third, differences in workload are associated with differences in error rate, task completion time, and user experience but the strength of association is merely slight to fair. Fourth, differences in opposite directions between workload and either error rate, task completion time, or user experience are few but occur for all TLX subscales. Fifth, differences in workload dimensions are more often associated with differences in tasks and contexts than users and systems. Sixth, the TLX subscales – not just the composite TLX score – are widely used for testing cross-system differences in workload.

Large-scale generic systems are typically adapted to local practice through configuration. This is especially important in healthcare, which involves a plurality of institutions and users. However, the decision to acquire a generic system in public healthcare is typically founded on regional and national health policy goals, which often are translated into various forms of standardization. As a result, national and regional health policy interests may stand in contrast to interests on the local level. Therefore, we analyze how national and local concerns are weighed against each other in the preparations for implementing large-scale generic systems in healthcare. We explore what role configuration plays and what the prospects are for long-term development. We contribute with insight into how the organizational consequences of generic systems are formed already in the preparation phase and point to how configuration easily results in standardization, thereby basically privileging national and regional health goals at the expense of local needs. Empirically, we focus on the preparations for implementing the Epic electronic health record in Central Norway.

Abstract Makerspaces are places for construction and creative expression using tools such as 3D printers, laser cutters, and sewing machines. In this study, we investigate how makers obtain information for their makerspace projects. The study focuses on four sources of information: people, documents, experimentation, and prior knowledge. On the basis of interviews with 13 makers, we analyze their use of these information sources in relation to different knowledge areas, creative‐process stages, and relevance criteria. Our main findings are that (a) experimentation is a prime source of information, (b) ease and pleasure are the dominant relevance criteria, (c) process and situation receive little attention, and (d) information sources vary across process stages. Specifically, experimentation is the dominant information source during the construction stage. In addition, the relevance criteria show that the makers turn to people because it is pleasurable, to documents because it is easy, and to experimentation because it results in quality products. These results emphasize the importance of experimentation and suggest that it warrants closer attention in studies of the information behavior of makers and, more broadly, creative professionals.

We investigate professional greenhouse growers’ user experience (UX) when using climate-management systems in their daily work. We build on the literature on UX, in particular UX at work, and extend it to ordinary UX at work . In a 10-day diary study, we collected data with a general UX instrument (AttrakDiff), a domain-specific instrument, and interviews. We find that AttrakDiff is valid at work; its three-factor structure of pragmatic quality (PQ), hedonic identification quality, and hedonic stimulation quality is recognizable in the growers’ responses. In this article, UX at work is understood as interactions among technology, tasks, structure, and actors. Our data support the recent proposal for the ordinariness of UX at work. We find that during continued use, UX at work is middle-of-the-scale, remains largely constant over time, and varies little across use situations. For example, the largest slope of the four AttrakDiff constructs when regressed over the 10 days was as small as 0.04. The findings contrast existing assumptions and findings in UX research, which is mainly about extraordinary and positive experiences. In this way, the present study contributes to UX research by calling attention to the mundane, unremarkable, and ordinary UXs at work.

In his article “The Usability Construct: A Dead End?” Noam Tractinsky (Human–Computer Interaction 2017) contends that for scientific research on usability to progress, the usability construct shoul...

Understanding the mechanisms that shape the adoption and use of information technology is central to human--computer interaction. Two accounts are particularly vocal about these mechanisms, namely the technology acceptance model (TAM) and work on user experience (UX) models. In this study, we review 37 papers in the overlap between TAM and UX models to explore the experiential component of human--computer interactions. The models provide rich insights about what constructs influence the experiential component of human--computer interactions and about how these constructs are related. For example, the effect of perceived enjoyment on attitude is stronger than those of perceived usefulness and perceived ease of use. It is less clear why the relations exist and under which conditions the models apply. We discuss four of the main theories used in reasoning about the experiential component and, for example, point to the near absence of psychological needs and negative emotions in the models. In addition, most of the reviewed studies are not tied to specific use episodes, thereby bypassing tasks as an explanatory variable and undermining the accurate measurement of experiences, which are susceptible to moment-to-moment changes. We end by summarizing the implications of our review for future research.

Studies have shown that whiteboards support much cooperative work by for example strengthening awareness, improving communication, and reducing mental workload. In line with these predominantly positive findings, an emergency department (ED) turned to its whiteboard to improve the coordination of its work with blood tests. We investigate this use of the whiteboard through observations and informal interviews in the ED and analyze the ability of the whiteboard to support coordination and awareness in the work with blood tests. Our findings show limitations in the ability of the whiteboard to support awareness in a setting where the users are (locally) mobile, specifically in regard to information that requires continuous monitoring. We do however also find that the whiteboard safeguarded the work with blood tests against some risks by making blood-test information socially visible.

The value of thinking aloud in usability tests depends on the content of the users’ verbalizations. We investigated moderated and unmoderated users’ verbalizations during relaxed thinking aloud (i.e., verbalization at Levels 1–3). Verbalizations of user experience were frequent and mostly relevant to the identification of usability issues. Explanations and redesign proposals were also mostly relevant, but infrequent. The relevance of verbalizations of user experience, explanations, and redesign proposals showed the value of relaxed thinking aloud but did not clarify the trade-off between rich verbalizations and test reactivity. Action descriptions and system observations—two verbalization categories consistent with both relaxed and classic thinking aloud—were frequent but mainly of low relevance. Across all verbalizations, the positive or negative verbalizations were more often relevant than those without valence. Finally, moderated and unmoderated users made largely similar verbalizations, the main difference being a higher percentage of high-relevance verbalizations by unmoderated users.

Usability evaluation is essential to user-centred design; yet, evaluators who analyse the same usability test sessions have been found to identify substantially different sets of usability problems. We revisit this evaluator effect by having 19 experienced usability professionals analyse video-recorded test sessions with five users. Nine participants analysed moderated sessions; 10 participants analysed unmoderated sessions. For the moderated sessions, participants reported an average of 33% of the problems reported by all nine of these participants and 50% of the subset of problems reported as critical or serious by at least one participant. For the unmoderated sessions, the percentages were 32% and 40%. Thus, the evaluator effect was similar for moderated and unmoderated sessions, and it was substantial for the full set of problems and still present for the most severe problems. In addition, participants disagreed in their severity ratings. As much as 24% (moderated) and 30% (unmoderated) of the problems reported by multiple participants were rated as critical by one participant and minor by another. The majority of the participants perceived an evaluator effect when merging their individual findings into group evaluations. We discuss reasons for the evaluator effect and recommend ways of managing it.

The mental workload imposed by systems is important to their operation and usability. Consequently, researchers and practitioners need reliable, valid, and easy-to-administer methods for measuring mental workload. The ratio of perceived time to clock time appears to be such a method, yet mental workload has multiple dimensions of which the perceived time ratio has mainly been linked to the task-related dimension. This study investigates how the perceived time ratio is affected by time constraints, which make time an explicit concern in the execution of tasks, and task success, which is a performance-related rather than task-related dimension of mental workload. A higher perceived time ratio is found for timed than untimed tasks. According to subjective workload ratings and pupil-diameter measurements, the timed tasks impose higher mental workload. This finding contradicts the prospective paradigm, which asserts that perceived time decreases with increasing mental workload. A higher perceived time ratio was also found for solved than unsolved tasks, whereas subjective workload ratings indicate lower mental workload for the solved tasks. This finding shows that the relationship between the perceived time ratio and mental workload is reversed for task success compared to time constraints. Implications for the use of perceived time as a measure of mental workload are discussed.

In point-and-click interfaces the location of targets is sometimes known to the user before visually identifying it, and sometimes not. This experiment investigates how pointing is affected by whether the target location is precued so that users know it in advance or nonprecued so that users learn it only at the onset of pointing trials. The study investigates this for young, adult, and elderly participants pointing with mouse and touchpad. Target precuing affects the trial completion time, the reaction time, the sheer movement time, and multiple movement kinematics. In addition, target precuing interacts with the use of either mouse or touchpad, with target distance, and with target size, but surprisingly little with participant age. Because the target location was always made known to participants no later than at the onset of the pointing trial, the effects of target precuing must be due to the different possibilities for mental and motor preparations.

Thinking aloud is widely used for usability evaluation, and its reactivity is therefore important to the quality of evaluation results. This study investigates whether thinking aloud (i.e., verbalization at Levels 1 and 2) affects the behavior of users who perform tasks that involve interruptions and time constraints, two frequent elements of real-world activities. The study finds that the presence of auditory, visual, audiovisual, or no interruptions interacts with thinking aloud for task solution rate, task completion time, and participants' fixation rate. Thinking-aloud participants also spend longer responding to interruptions than control participants. Conversely, the absence or presence of time constraints does not interact with thinking aloud, suggesting that time pressure is less likely to make thinking aloud reactive than previously assumed. These results inform practitioners faced with the decision to either restrict verbalizations in usability evaluation to thinking aloud to avoid reactivity or relax the constraints on verbalization to obtain additional information.

Whereas the concept of usability is predominantly defined analytically, people relate to systems through personal usability constructs. Based on 48 repertory-grid interviews, this study investigates how such personal constructs are affected by two factors crucial to the international development and uptake of systems: nationality (Chinese, Danish, or Indian) and stakeholder group (developer or user). We find no significant overall difference across nationalities, but further analyses suggest that conventional usability aspects such as ease of use and simplicity are prominent for Chinese and Danish but not Indian participants and that a distinction between work and leisure-related communication is central to Chinese and Indian but not Danish participants. For stakeholder groups, we find a significant overall difference between developers and users. Unlike developers, users associate ease of use with leisure and, conversely, difficulty in use with work-relatedness. Further, users perceive usefulness as related to frustration and separate from ease of use, whereas developers construe usefulness, fun, and ease of use as related. In construing usability, participants make use of several constructs that are not part of prevailing usability definitions, including usefulness, fun, and security.

The selection of users for participation in IT projects involves trade-offs between multiple criteria, one of which is selecting a representative cross-section of users. This criterion is basic because trading it for other criteria means basing designs on information biased toward some user groups at the expense of others. Based on interviews in development and customer organizations we find that their criteria for user selection favour persons who can contribute to the progress of the IT project over persons who are representative of the full range of users. A highly valued contribution from participating users is the ability to advocate a vision for the system and champion its organizational implementation. A survey in one customer organization shows that respondents’ personal traits explain up to 31% of the variation in their experience of aspects of the usability of a recently introduced system. Thus, unless participating users are representative as to these personal traits, IT projects may, inadvertently, bring about systems that will fail to satisfy many users.

The term usability is ubiquitous in human–computer interaction, so much so that it is commonly used without definition. Rather than one established meaning of usability, there are, however, multiple images of usability. Although each image provides a partial view, the partiality remains implicit unless confronted with alternative images. This study delineates six images of usability: universal usability, situational usability, perceived usability, hedonic usability, organizational usability, and cultural usability. The different foci of the images provide opportunities for becoming sensitized to manifold aspects of the use of a system and thereby acquiring a genuine understanding of its usability. The six images differ, for example, in the extent to which they include aspects of the outcome of the process of using a system or merely the process of use, whether they involve collaborative use or merely individual use, and in their view of usability as perceived by individuals or shared by groups. Several challenges result from recognizing that usability is a set of images rather than a coherent concept, including a risk of misunderstandings in discussions of usability because participants may assume different images of usability and a need for supplementary methods addressing the collaborative and long-term aspects of usability. Moreover, the images call for extending the scope of practical usability work to include the effects achieved by users during their use of systems for real work.

Effects of age on pointing performance have become increasingly important as computers have become extensively used by still larger parts of the population. This study empirically investigates young (12–14 years), adult (25–33 years), and elderly (61–69 years) participants' performance when pointing with mouse and touchpad. The goal is to provide an integrated analysis of (a) how these three age groups differ in pointing performance, (b) how these differences are affected by the two pointing devices, and (c) how the submovement structure of cursor trajectories may explain performance differences. Results show that adult participants perform better than both young and elderly participants in that adult participants make fewer errors than young participants and complete trials quicker than elderly participants. Moreover, young participants are quicker than elderly participants, who make neither more nor less errors than young and adult participants. All three age groups were slower and made more errors with the touchpad than the mouse, but the touchpad slowed down elderly participants more than young participants, who in turn were slowed down more than adult participants. Adult participants made more efficient submovements than elderly participants; young participants had an intermediate position in that they were similar to adult participants for some submovement measures and similar to elderly participants for others.

Most research assumes that usability is understood similarly by users in different cultures, implying that the notion of usability, its aspects, and their interrelations are constant across cultures. The present study shows that this is not the case for a sample of 412 users from China and Denmark, who differ in how they understand and prioritize different aspects of usability. Chinese users appear to be more concerned with visual appearance, satisfaction, and fun than Danish users; Danish users prioritize effectiveness, efficiency, and lack of frustration higher than Chinese users. The results suggest that culture influences perceptions of usability. We discuss implications for usability research and for usability practice.

Successful deployment of information technology (IT) involves implementation of new ways of working. Under-recognition of this organizational element of implementation entails considerable risk of not attaining the benefits that motivated deployment, yet knowledge of how to work systematically with organizational implementation is sparse. This study investigates a set of interventions undertaken to implement one mandated procedure associated with an electronic medication record, namely that all information about medication is recorded in the system. Medical record audits show that the interventions, which were devised and performed as part of the study, significantly lowered the number of records that violated the procedure. This positive effect was, however, not achieved until multiple interventions had been employed, and there is some indication that the effect may be wearing off after the interventions have ended. We discuss the implications of these results for efforts to work systematically with the organizational implementation of IT systems.

Thinking aloud is widely used for usability evaluation. The validity of the method is, however, debatable because it is generally used in a relaxed way that conflicts with the prescriptions of the classic model for obtaining valid verbalisations of thought processes. This study investigates whether participants that think aloud in the classic or relaxed way behave differently compared to performing in silence. Results indicate that whereas classic thinking aloud has little or no effect on behaviour apart from prolonging tasks, relaxed thinking aloud affects behaviour in multiple ways. During relaxed thinking aloud participants took longer to solve tasks, spent a larger part of tasks on general distributed visual behaviour, issued more commands to navigate both within and between the pages of the websites used in the experiment, and experienced higher mental workload. Implications for usability evaluation are discussed.

We discuss the impact of cultural differences on usability evaluations that are based on the thinking-aloud method (TA). The term ‘cultural differences’ helps distinguish differences in the perception and thinking of Westerners (people from Western Europe and US citizens with European origins) and Easterners (people from China and the countries heavily influenced by its culture). We illustrate the impact of cultural cognition on four central elements of TA: (1) instructions and tasks, (2) the user’s verbalizations, (3) the evaluator’s reading of the user, and (4) the overall relationship between user and evaluator. In conclusion, we point to the importance of matching the task presentation to users’ cultural background, the different effects of thinking aloud on task performance between Easterners and Westerners, the differences in nonverbal behaviour that affect usability problem detection, and, finally, the complexity of the overall relationship between a user and an evaluator with different cultural backgrounds.

Fisheye menus have become a prominent example of fisheye interfaces, yet contain several nonfisheye elements and have not been systematically evaluated. This study investigates whether fisheye menus are useful, and tries to untangle the impact on usability of the following properties of fisheye menus: use of distortion, index of letters for coarse navigation, and the focus-lock mode for accurate movement. Twelve participants took part in an experiment comparing fisheye menus with three alternative menu designs across known-item and browsing tasks, as well as across alphabetical and categorical menu structures. The results show that for finding known items, conventional hierarchical menus are the most accurate and by far the fastest. In addition, participants rate the hierarchical menu as more satisfying than fisheye and multifocus menus, but do not consistently prefer any one menu. For browsing tasks, the menus neither differ with respect to accuracy nor selection time. Eye-movement data show that participants make little use of nonfocus regions of the fisheye menu, though these are a defining feature of fisheye interfaces. Nonfocus regions are used more with the multifocus menu, which enlarges important menu items in these regions. With the hierarchical menu, participants make shorter fixations and have shorter scanpaths, suggesting lower requirements for mental activity and visual search. We conclude by discussing why fisheye menus are inferior to the hierarchical menu and how both may be improved.

Severity assessments enable prioritization of problems encountered during usability evaluations, and thereby provide a device for guiding the utilization of design resources. However, designers' response to usability evaluations is also influenced by other factors, which may overshadow severity. With the purpose of enhancing the impact of severity assessments, this study combines a field study of factors that influence the impact of evaluations with an experimental study of severity assessments made during usability inspections. The results show that even in a project receptive to input from evaluations, their impact was highly dependent on conducting evaluations early. This accorded with an informal method that blended elements of usability evaluation and participatory design and could be extended with user-made severity assessments. The major cost associated with the evaluations was not finding but fixing problems, emphasizing that, to be effective, severity assessments must be reliable, valid, and sufficiently persuasive to justify the cost of fixing problems. For the usability inspections, evaluators' ratings of problem impact and persistence were weakly correlated with the number of evaluators reporting a problem, indicating that different evaluators represent different subgroups of users or alternatively that evaluator-made severity assessments are of questionable reliability. To call designers' attention to the severe problems, the halving of the severity sum is proposed as a means of visualizing the large payoff of fixing a high-severity problem and, conversely, the modest potential of spending resources on low-severity problems.

This paper argues that proactive behaviour, caused by high engagement and motivation of the learners, may lead to failure of collaborative learning. By examining empirical data from real-world text-only virtual negotiations between dispersed participants engaged in project-based collaborative learning, we discover that volunteering self-initiated activities promotes the participants' individualistic behaviour. Also, the technology made it easy for participants to include their own statements in new contributions and deconstruct the statements of others, permitting few opportunities for others to influence proposals.

This study investigates the role of rhythms in the collaborative coordination of mobile work as well as in the individual actors' comprehension and command of their work. Drawing on an ethnographic study of home-care work, we examine the ways in which temporal regularities or rhythms are formed and reinforced. Further, we analyse how the major temporal rhythms are configured and furnished by individual, collective, and social rhythms, and how these rhythms contribute to the collaborative flow of activities. Finally, we discuss how the concept of rhythms adds to an understanding of alignment and coordination in mobile and distributed work settings.

Touchpad devices are widely used but lacking in pointing efficiency. The TouchGrid, an instance of what we term cell cursors, replaces moving the cursor through dragging the finger on a touchpad with tapping in different regions of the touchpad. The touchpad regions are recursively mapped to smaller display regions and thereby enable high-precision pointing without requiring high tapping precision. In an experiment, six subjects used the TouchGrid and a standard touchpad across different numbers of targets, distances to targets and target widths. Whereas standard touchpad operation follows Fitts' law, target selection time with the TouchGrid is a linear function of the required number of taps. The TouchGrid was significantly faster for small targets and for tasks requiring one tap, and marginally faster for two-tap tasks. Error rates tended to be higher with the TouchGrid than the standard touchpad. All subjects preferred the TouchGrid.

Computer professionals have a need for robust, easy-to-use usability evaluation methods (UEMs) to help them systematically improve the usability of computer artifacts. However, cognitive walkthrough (CW), heuristic evaluation (HE), and thinking- aloud study (TA)-3 of the most widely used UEMs-suffer from a substantial evaluator effect in that multiple evaluators evaluating the same interface with the same UEM detect markedly different sets of problems. A review of 11 studies of these 3 UEMs reveals that the evaluator effect exists for both novice and experienced evaluators, for both cosmetic and severe problems, for both problem detection and severity assessment, and for evaluations of both simple and complex systems. The average agreement between any 2 evaluators who have evaluated the same system using the same UEM ranges from 5% to 65%, and no 1 of the 3 UEMs is consistently better than the others. Although evaluator effects of this magnitude may not be surprising for a UEM as informal as HE, it is certainly notable that a substantial evaluator effect persists for evaluators who apply the strict procedure of CW or observe users thinking out loud. Hence, it is highly questionable to use a TA with 1 evaluator as an authoritative statement about what problems an interface contains. Generally, the application of the UEMs is characterized by (a) vague goal analyses leading to variability in the task scenarios, (b) vague evaluation procedures leading to anchoring, or (c) vague problem criteria leading to anything being accepted as a usability problem, or all of these. The simplest way of coping with the evaluator effect, which cannot be completely eliminated, is to involve multiple evaluators in usability evaluations.

The notion of trust has been virtually absent from most work on how people assess and choose their information sources. Based on two empirical cases this study shows that software engineers and users of e-commerce websites devote a lot of attention to considerations about the trustworthiness of their sources, which include people, documents, and virtual agents. In the project-based software engineering environment trust tends to be a collaborative issue and the studied software engineers normally know their sources first-hand or have them recommended by colleagues. Outside this network people are cautious and alert to even feeble cues about source trustworthiness. For example, users of e-commerce websites—generally perceived as single-user environments—react rather strongly to the visual appearance of virtual agents, though this is clearly a surface attribute. Across the two cases people need access to their sources in ways that enable them to assess source trustworthiness, access alone is not enough.

Computer professionals have a need for robust, easy-to-use usability evaluation methods (UEMs) to help them systematically improve the usability of computer artifacts. However, cognitive walkthrough (CW), heuristic evaluation (HE), and thinking- aloud study (TA)-3 of the most widely used UEMs-suffer from a substantial evaluator effect in that multiple evaluators evaluating the same interface with the same UEM detect markedly different sets of problems. A review of 11 studies of these 3 UEMs reveals that the evaluator effect exists for both novice and experienced evaluators, for both cosmetic and severe problems, for both problem detection and severity assessment, and for evaluations of both simple and complex systems. The average agreement between any 2 evaluators who have evaluated the same system using the same UEM ranges from 5% to 65%, and no 1 of the 3 UEMs is consistently better than the others. Although evaluator effects of this magnitude may not be surprising for a UEM as informal as HE, it is certainly notable that a substantial evaluator effect persists for evaluators who apply the strict procedure of CW or observe users thinking out loud. Hence, it is highly questionable to use a TA with 1 evaluator as an authoritative statement about what problems an interface contains. Generally, the application of the UEMs is characterized by (a) vague goal analyses leading to variability in the task scenarios, (b) vague evaluation procedures leading to anchoring, or (c) vague problem criteria leading to anything being accepted as a usability problem, or all of these. The simplest way of coping with the evaluator effect, which cannot be completely eliminated, is to involve multiple evaluators in usability evaluations.

Usability comprises the aspects effectiveness, efficiency, and satisfaction. The correlations between these aspects are not well understood for complex tasks. We present data from an experiment where 87 subjects solved 20 information retrieval tasks concerning programming problems. The correlation between efficiency, as indicated by task completion time, and effectiveness, as indicated by quality of solution, was negligible. Generally, the correlations among the usability aspects depend in a complex way on the application domain, the user's experience, and the use context. Going through three years of CHI Proceedings, we find that 11 out of 19 experimental studies involving complex tasks account for only one or two aspects of usability. When these studies make claims concerning overall usability, they rely on risky assumptions about correlations between usability aspects. Unless domain specific studies suggest otherwise, effectiveness, efficiency, and satisfaction should be considered independent aspect of usability and all be included in usability testing.

A user interface study concerning the usage effectiveness of selected retrieval modes was conducted using an experimental text retrieval system, TeSS, giving access to online documentation of certain programming tools. Four modes of TeSS were compared: (1) browsing, (2) conventional boolean retrieval, (3) boolean retrieval based on Venn diagrams, and (4) these three combined. Further, the modes of TeSS were compared to the use of printed manuals. The subjects observed were 87 computing new to them. In the experiment the use of printed manuals is faster and provides answers of higher quality than any of the electronic modes. Therefore, claims about the effectiveness of computer-based text retrieval have to by vary in situations where printed manuals are manageable to the user. Among the modes of TeSS, browsing is the fastest and the one causing the fewest operational errors. On the same two variables, time and operational errors, the Venn diagram mode performs better than conventional boolean retrieval. The combined mode scores worst on the objective performance measures; nonetheless nearly all subject prefer this mode. Concerning the interaction process, the subjects tend to manage the complexities of the information retrieval tasks by issuing series of simple commands and exploiting the interactive capabilities of TeSS. To characterize the dynamics of the interaction process two concepts are introduced; threads and sequences of tactics. Threads in a query sequence describes the continuity during retrieval. Sequences of tactics concern the combined mode and describe how different retrieval modes succeed each other as the retrieval process evolves.