Mothers of preschool children with cerebral palsy are often responsible for delivering multiple home therapy programs. Technology could be a way to bridge some of the challenges of home therapy delivery, such as lack of regular contact with professionals and the need for support continuity. We interviewed seven mothers and four speech therapists to explore their challenges, and the types of support they currently receive (or give). Key issues included limitations of existing communication channels between mothers and professionals, the mothers’ social support needs, and the level of commitment required to self-deliver home therapy. Based on findings indicating video sharing as an existing practice among mothers, we conducted three workshops to further investigate how a video-based platform could support home therapy delivery. We conclude with a number of design considerations for such technologies, to improve communication and collaboration between professional therapists, mothers and members of their wider social network.

We report upon the conduct and findings of an investigation into technology design for long-distance relationships (LDRs), where South Korean culture raises specific challenges. Through two qualitative studies we explore inter-generational LDRs from the perspective of South Korean students based in the United Kingdom. We identify and document the particular nuances within, and challenges that arise from, these relationships, before turning to the pragmatics of technology design for LDRs. Through both an extended diary study and interviews with students, we illustrate the impact of Korean familial obligations on intergenerational LDRs, and the mistrust and anxiety on both sides (parents and students) arising from limitations in communication channels. From our findings, we develop the notion of 'respectful disconnection' which we propose as a framework for designing interactions that appropriately support LDRs within this specific South Korean context.

We present findings from a qualitative study about how Internet use supports self-functioning following the life transition of retirement from work. This study recruited six recent retirees and included the deployment of OnLines, a design research artifact that logged and visualized key online services used by participants at home over four-weeks. The deployment was supported by pre- and post-deployment interviews. OnLines prompted participants' reflection on their patterns of Internet use. Position Exchange Theory was used to understand retirees' sense making from a lifespan perspective, informing the design of supportive online services. This paper delivers a three-fold contribution to the field of human-computer interaction, advancing a lifespan-oriented approach by conceptualizing the self as a dialogical phenomenon that develops over time, advancing the ageing discourse by reporting on retirees' complex identities in the context of their life histories, and advancing discourse on research through design by developing OnLines to foster participant-researcher reflection informed by Self Psychology.

This paper reports on a qualitative study of 38 low-income individuals living in the North East of England. The participants' experiences of money, banking and the role digital technology plays in their financial practices were identified through semi-structured interviews in people's homes and group workshops. A grounded theory analysis of these data characterises how technology both helped and hindered participants to keep close control of their finances. These findings suggest design opportunities for future digital banking technologies that extend the already sophisticated practices of individuals managing a low income, focusing on: delaying, prioritising, planning, watching, and hiding monetary transactions.

Delegation is the practice of sharing authority with another individual to enable them to complete a specific task as a proxy. Practices to permit delegation can range from formal to informal arrangements and can involve spontaneous yet finely balanced notions of trust between people. This paper argues that delegation is a ubiquitous yet an unsupported feature of socio-technical computer systems and that this lack of support illustrates a particular neglect to the everyday financial practices of the more vulnerable people in society. Our contribution is to provide a first exploration of the domain of person-to-person delegation in digital payments, a particularly pressing context. We first report qualitative data collected across several studies concerning banking practices of individuals over 80 years of age. We then use analytical techniques centred upon identification of stakeholders, their concerns and interactions, to characterize the delegation practices we observed. We propose a Concerns Matrix as a suitable representation to capture conflicts in the needs of individuals in such complex socio-technical systems, and finally propose a putative design response in the form of a Helper Card.

This paper explores and evaluates two techniques that measure aspects of social behaviour as an indicator of experience. The rationale driving the work is the idea that experience is entwined with social interaction and so, while experience itself is difficult to quantify, we might tap into it by measuring aspects of conversation that are related to it. Two techniques are considered as possible ways of doing this: (i) process measures of social behaviour derived from video analysis and (ii) thin-slice ratings ascribed by naïve judges. Regarding (i), process measures of conversational equality, freedom and number of turns are shown to be reliable, sensitive and linked to unfolding experience. Regarding (ii), a Thin Slice Enjoyment Scale is developed and shown to be a reliable and less time-consuming, but also less sensitive, alternative to the process measures. Both methods are of interest to researchers and practitioners who would wish to assess user experience in a group context. Additionally, analysis of the process measures is of broader relevance to researchers who conduct quantitative analyses of talk.

Invisible Design is a technique for generating insights and ideas with workshop participants in the early stages of concept development. It involves the creation of ambiguous films in which characters discuss a technology that is not directly shown. The technique builds on previous work in HCI on scenarios, persona, theatre, film and ambiguity. The Invisible Design approach is illustrated with three examples from unrelated projects; Biometric Daemon, Panini and Smart Money. The paper presents a qualitative analysis of data from a series of workshops where these Invisible Designs were discussed. The analysis outlines responses to the films in terms of; existing problems, concerns with imagined technologies and design speculation. It is argued that Invisible Design can help to create a space for critical and creative dialogue during participatory concept development.

This paper describes a project exploring the design of digital payment services in collaboration with 16 people aged over 80. Many older people find cheques valuable as a means of payment but the UK Payments Council recently proposed their abolition. We describe two designs that simultaneously aimed to preserve and augment the paper cheque as a means of making electronic payments. These were devised during participatory design workshops through critical dialogues with our eighty something participants. Workshop discussions resulted in the creation of a real world cheque system where we issued pre-paid cheques without the involvement of banks. This work informed the development of a digital cheque book based on Anoto digital pen technology. The work illustrates the value of participatory design with 'extraordinary' users, such as the eighty somethings, in HCI.

This paper reports findings from a series of participatory design workshops with ten people over eighty years old. The focus of the workshops was new banking technologies for the older old. Participants were asked to discuss their current experiences of banking and given packs of concept cards which contained design sketches and brief outlines of concepts for new financial services. The designs on the cards were deliberately provocative and aimed to encourage criticism and debate. Participants wrote and drew on the cards and the workshops were recorded and transcribed. The participants were extremely critical of current banking practices and most of the new concepts we presented to them. Their questions and comments led to a number of insights and further iterations. The paper argues that critique is an essential resource for design, both in terms of identifying problems and iterating ideas.

A cheque is a paper document that orders the transfer of money between bank accounts. Whilst an eighty-year-old in the UK is predicted on average to live at least another ten years, cheques may not. Despite many older peoples extensive use of cheques, UK banks are eager to abolish them and design electronic alternatives that are less costly to process and less vulnerable to fraud. This paper reports on two qualitative studies that explored the banking experiences of 23 people over eighty years old. Cheques support financial collaboration with others in ways that digital payment systems do not. We argue that whilst it might be possible to improve the design of digital payment systems to better support financial collaboration, the case for retaining and enhancing cheques is stronger. Rather than replace cheques, we must design ways of making them less costly to process and better linked to electronic payment methods.

The ratio of healthcare professionals to care recipients is dropping at an alarming rate, particularly for the older population. It is estimated that the number of persons with Alzheimer's disease, for example, will top 100 million worldwide by the year 2050 [Alzheimer's Disease International 2009]. It will become harder and harder to provide needed health services to this population of older adults. Further, patients are becoming more aware and involved in their own healthcare decisions. This is creating a void in which technology has an increasingly important role to play as a tool to connect providers with recipients. Examples of interactive technologies range from telecare for remote regions to computer games promoting fitness in the home. Currently, such technologies are developed for specific applications and are difficult to modify to suit individual user needs. The future potential economic and social impact of technology in the healthcare field therefore lies in our ability to make intelligent devices that are customizable by healthcare professionals and their clients, that are adaptive to users over time, and that generalize across tasks and environments. A wide application area for technology in healthcare is for assistance and monitoring in the home. As the population ages, it becomes increasingly dependent on chronic healthcare, such as assistance for tasks of everyday life (washing, cooking, dressing), medication taking, nutrition, and fitness. This article will present a summary of work over the past decade on the development of intelligent systems that provide assistance to persons with cognitive disabilities. These systems are unique in that they are all built using a common framework, a decision-theoretic model for general-purpose assistance in the home. In this article, we will show how this type of general model can be applied to a range of assistance tasks, including prompting for activities of daily living, assistance for art therapists, and stroke rehabilitation. This model is a Partially Observable Markov Decision Process (POMDP) that can be customized by end-users, that can integrate complex sensor information, and that can adapt over time. These three characteristics of the POMDP model will allow for increasing uptake and long-term efficiency and robustness of technology for assistance.

A review of 15 papers reporting 25 independent correlations of perceived beauty with perceived usability showed a remarkably high variability in the reported coefficients. This may be due to methodological inconsistencies. For example, products are often not selected systematically, and statistical tests are rarely performed to test the generality of findings across products. In addition, studies often restrict themselves to simply reporting correlations without further specification of underlying judgmental processes. The present study's main objective is to re-examine the relation between beauty and usability, that is, the implication that “what is beautiful is usable.” To rectify previous methodological shortcomings, both products and participants were sampled in the same way and the data aggregated both by averaging over participants to assess the covariance across ratings of products and by averaging over products to assess the covariance across participants. In addition, we adopted an inference perspective to qualify underlying processes to examine the possibility that, under the circumstances pertaining in most studies of this kind where participants have limited experience of using a website or product, the relationship between beauty and usability is mediated by goodness. A mediator analysis of the relationship between beauty, the overall evaluation (i.e., “goodness”) and pragmatic quality (as operationalization of usability) suggests that the relationship between beauty and usability has been overplayed as the correlation between pragmatic quality and beauty is wholly mediated by goodness. This pattern of relationships was consistent across four different data sets and different ways of data aggregation. Finally, suggestions are made regarding methodologies that could be used in future studies that build on these results.

Technologies from pervasive computing can be used to ameliorate the difficulties that people with dementia have with multi-step tasks. This paper is intended to inform the design of technologies that help people perform daily tasks, by prompting them when they have difficulties, thus fostering independence and quality of life. Six people with mild to moderate dementia were video recorded performing activities of their own choosing in the familiar context of their own kitchens. In total there were 22 video recordings. Activities included making a cup of tea or coffee, a bowl of soup, beans on toast, or coffee with toast. The video recordings were transcribed using an adapted version of the Action Coding System. Incidents, where prompting was judged to be needed were categorised using a data-driven analysis as problems in: Sequencing (intrusion, omission and repetition), Finding things (locating and identifying), Operation of appliances, and Incoherence (toying and inactivity). Detailed examples of each type of incident, and the contexts in which it occurred, are provided as a resource for the design of pervasive computing solutions. What needs to be detected and what form prompts might take is specified for each category.

A pragmatic approach to interaction modeling is presented by which a designer can describe how the user gets tasks done with a newly developing system. The notation proposed allows an interaction designer to make explicit both how user actions cause visible or noticeable changes in the state of the machine and how the user is expected to use this feedback to generate the next action. Interaction Unit (IU) scenarios are constructed where each IU specifies one step in the cycle of interaction. Each IU specifies the visible system state that leads the user to take some action. In addition, the IU makes explicit the state of the goal stack at the start and end of the unit and the mental processes (recall, recognition, or affordance) required. In this way one can describe the intimate connection between goal, action, and the environment in user–machine interaction. To demonstrate the completeness of IU scenario analysis, IU models are presented for some well-known problems in interaction design: hidden and partially hidden modes leading to unexpected system effects, insufficient cues for subgoal construction, insufficient cues for subgoal elimination, and inappropriate affordances for action. These scenarios are accompanied by procedures that designers can use to detect similar problems in putative interaction designs. To demonstrate the feasibility of using IU scenario analysis in design, 4 graduate students were taught to use IU scenario analysis in a 3-hr session. They then worked as a group to evaluate a prototype handheld warehouse application. A comparable group was taught and then applied Cognitive Walkthrough. Both groups successfully completed the task and detected several problems rated as being of high severity by the designers of the prototype. Analysis of the problems detected by each group suggests that the two techniques are complimentary. IU scenario analysis may be most cost-effective for devices using new interaction paradigms, whereas Cognitive Walkthrough may be most cost-effective for designs using established interaction paradigms.

Using qualitative data, Blom and Monk (2003 Blom, J. and Monk, A. 2003. A theory of personalisation: why people personalise their PCs and mobile phones. Human Computer Interaction, 18: 193–228. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) derived a theory of why people choose to personalise the appearance of their PCs and mobile phones. This paper describes some quantitative data that provide some support for, and some modifications to, the theory. Individuals having personal home pages were recruited to fill in a questionnaire that assesses dispositions to personalise and its effects. In addition the 82 home pages were inspected to assess the extent of personalisation. This correlated significantly with the dispositions ‘Frequency of Use’ and ‘Knowledge of Personalisation’. The questionnaire items corresponding to effects were factor analysed. A four-factor solution suggested item groupings similar, but not identical, to those used in the theory. There are significant positive correlations between the extent of personalisation and cognitive effects and enduring emotional effects. The value of quantitative data for confirming and refining a qualitative theory is discussed.

This paper describes the development of Net Neighbours, an online shopping scheme that widens Internet access to older people via volunteer telephone intermediaries. It outlines the processes of: problem identification, designing the telephone interaction, the financial model and the interface for the volunteer. It describes the application and adaptation of Human Computer Interaction (HCI) techniques to address the needs of the local charity that co-developed the scheme. The paper begins by reporting the ethnographic work that led to the scheme; it then describes the pilot study conducted with Age Concern, York. It maps the various possible configurations for the scheme in a series of financial models expressed in tree diagrams and goes on to describe the use of pastiche scenarios in developing designs. Pastiche scenarios draw on fiction as a resource to explore, in an engaging manner, the social issues raised by technological innovations; the paper presents extracts from three such scenarios that were used to reason about dependability issues with Age Concern staff. The scheme is ongoing and plans are currently being made to extend it by recruiting university staff and other office workers as volunteer intermediaries. It is hoped that the scheme will become widely available across the city and in other locations around the UK. It is argued that volunteer telephone intermediaries can bridge digital divides and make Internet services accessible to those excluded either by age, disability or lack of resources. The development of the scheme is a case study in the ways that HCI techniques can be adopted and adapted in order to design for civil society. 1

This paper considers the needs of an ageing population and the implications for Human Computer Interaction (HCI) research. The discussion is structured around findings from interviews with medical and care professionals and older people. Various technologies are being successfully used to monitor for falls and other emergencies, and also to assess and manage risk. The design of this technology is currently driven by a medical model of client needs and takes little account of the social context of the home. The design challenges for HCI are to make this technology attractive, provide privacy, allow informed choice and reduce rather than increase the isolation currently felt by many older people. It is argued that the ageing population presents a fundamental challenge to HCI in the need for socially dependable systems. Socially dependable systems take account of social context, the need for sociability and are accessible to all who need them.

While there are well established guidelines for interaction via mouse and keyboard, new forms of interaction being devised for small handheld devices have yet to be standardised. There is a case for re-visiting basic principles for user interface design such as how to signal mode. Two ways of signalling case mode when editing text into a small handheld device such as a mobile phone are considered in this paper. One is through the system prompt, e.g. ‘Entry:’, the other is through the case of the last letter displayed in response to a button push. Two unsupervised web-based experiments are described which show that users are sensitive to both these signals for case mode. The first experiment manipulated the prompt in a text entry task using a web simulation of a novel mobile device. The results showed that users’ expectations were influenced by the case of the letters in the prompt. Users took many more trials to learn to expect a case inconsistent with the model provided by the prompt. The second experiment manipulated both the case of the letters in the prompt and the case of the last letter displayed. The results replicated the findings above and demonstrated a strong effect of the case of the last letter displayed. Guidelines for signalling case mode and a notation (Interaction Units) are suggested that might be used to reason about low level interaction design with handheld devices.

Sixty four members of the public were exposed to the same staged conversation either while waiting in a bus station or travelling on a train. Half of the conversations were by mobile phone, so that only one end of the conversation was heard, and half were co present face-to-face conversations. The volume of the conversations was controlled at one of two levels: the actors' usual speech level and exaggeratedly loud. Following exposure to the conversation participants were approached and asked to give verbal ratings on six scales. Analysis of variance showed that mobile phone conversations were significantly more noticeable and annoying than face-to-face conversations at the same volume when the content of the conversation is controlled. Indeed this effect of medium was as large as the effect of loudness. Various explanations of this effect are explored, with their practical implications.

Mobile (cell) phone conversations are commonly perceived as annoying when conducted in a public space. An experiment is described that demonstrates one factor contributing to this phenomenon: hearing only one side of a conversation makes it more noticeable and intrusive. Two actors repeatedly staged the same conversation under three conditions: cell phone; normal, co-present both audible, and co-present only one audible. After the staged conversation, which took place on a train, a third person obtained verbal ratings from members of the travelling public. As in a previous experiment published in this journal, the cell phone conversation was rated as more noticeable and intrusive than the normal co-present both audible conversation. Critically, a new experimental condition, co-present one-audible, in which both actors were present but only one side of the conversation was heard, produced ratings equivalent to the cell phone condition. This ‘need-to-listen’ effect is discussed with regard to implications for design and theories of language use.

Three linked qualitative studies were performed to investigate why people choose to personalize the appearance of their PCs and mobile phones and what effects personalization has on their subsequent perception of those devices. The 1st study involved 35 frequent Internet users in a 2-stage procedure. In the 1st phase they were taught to personalize a commercial Web portal and then a recommendation system, both of which they used in the subsequent few days. In the 2nd phase they were allocated to 1 of 7 discussion groups to talk about their experiences with these 2 applications. Transcripts of the discussion groups were coded using grounded theory analysis techniques to derive a theory of personalization of appearance that identifies (a) user-dependent, system-dependent, and contextual dispositions; and (b) cognitive, social, and emotional effects. The 2nd study concentrated on mobile phones and a different user group. Three groups of Finnish high school students discussed the personalization of their mobile phones. Transcripts of these discussions were coded using the categories derived from the 1st study and some small refinements were made to the theory in the light of what was said. Some additional categories were added; otherwise, the theory was supported. In addition, 3 independent coders, naive to the theory, analyzed the transcripts of 1 discussion group each. A high degree of agreement with the investigators' coding was demonstrated. In the 3rd study, a heterogeneous sample of 8 people who used the Internet for leisure purposes were visited in their homes. The degree to which they had personalized their PCs was found to be well predicted by the dispositions in the theory. Design implications of the theory are discussed.

Mutual gaze is an important conversational resource, but is difficult to provide using conventional video conferencing equipment due to the disparity between the position of the camera and the position of the eyes on the screen. Various elaborate inventions have been proposed to get around this problem but none have found wide use. The alternative explored here is that these expensive alternatives may be unnecessary. Users of conventional desktop video equipment may, under the right conditions, be able to learn to interpret what is at first sight inappropriate apparent gaze direction as signalling that the other person is "looking at me."Data are presented from two experiments where an estimator judges where a gazer is looking. The gazer may be looking either at the desktop video image of the estimator or some point to the side. Experiment 1 compared two image sizes and two camera positions. While the size of the image (352 × 288 pixels versus 176 × 144) had no significant effect on participants' ability to judge where the gazer was looking, horizontally offsetting the position of the camera inhibited performance. Experiment 2 examined the effect of reducing the image size further. The smallest image size (88 × 72 pixels) resulted in poorer performance than the intermediate (176 × 144). The results show that it is possible for users of low cost desktop video conferencing to learn to interpret gaze direction to a very high degree of accuracy if the equipment is configured optimally. The practical and theoretical implications of these results are discussed.

Experiment 1 examined power of email communications, compared to equivalent printed communications, to influence a recipient's behaviour. 160 people were sent requests to volunteer for an experiment. Half received these requests through email and half on printed media through the internal mail. These groups were further subdivided into those who replied by internal or electronic mail. There was no evidence that an email message has less weight in persuading people to reply positively. The pattern of reply frequencies is completely explained by the relative effort required to reply. Experiment 2 examined recipients' reactions to email and print communications using rating scales. An email and printed text group were asked to rate two documents, a job application and a thank you note, on various qualities. While the content of the document had a significant effect on ratings, there was no evidence that recipients rate messages or their senders differently depending on the medium used. It is concluded that for this student population email has taken on many of the characteristics previously expected of print.

Human-computer interaction (HCI), and much other behaviour, can usefully be thought of as a continuous process of cyclic interaction with the environment. The action someone takes leads to changes to the state of the world. These are evaluated with respect to, and in a manner conditioned by, the user's current goals. This evaluation leads to the reformulation of goals and further action, leading to a new state of the environment, and so. A state-transition model that makes explicit the relationship between user and environment at each stage of interaction is developed that leads to two further representations: (i) the state-transition scenario describing a particular trajectory through the state space; (ii) the statetransition framework defining classes of state-transition model with empirical consequences. Display-driven cyclic models have received considerable attention in the recent HCI literature. One state-transition framework, corresponding to a class of these models, is shown to be inadequate as a theory of human- computer interaction.

The first part of this paper cautions against the injudicious use of citation data to rank journals. The second and main part presents a correspondence analysis of the descriptors assigned by abstractors to papers in five HCI, two human factors and three psychology journals. This analysis makes it possible to position the journals in a space of descriptors. The HCI journals form a cluster distinct from the psychology and human factors journals, suggesting HCI has now separated from its parent disciplines. Further, it is possible to position individual journals, for example, Behaviour & Information Technology is identified as an HCI journal with a leaning towards human factors.

The conceptual basis for designing procedures is confused by the problematics of characterizing a relation between procedures and work practices. As they emerge from scientific management theory, procedures connote a means of rationalizing and controlling work. However, interpretations of the use of procedures reveal differences in emphasis on the work required to relate procedures to practice, from comprehending to evaluating appropriateness or reasonableness. These evaluations point to a moral character in this work, which we characterize in terms of workers' concerns. Moreover, as conceptual differences in emphasis such as these can prove intractable, we argue that a more productive approach to resolving the problematics would be to evaluate the usefulness of a sensitivity to concerns in designing procedures. Three brief case studies of the use of procedures in safety-critical settings point to workers making judgments when relating procedures to their practice, including judgments of the value of the procedures they were using. These cases also demonstrated the complexity of concerns that were multiple and interacting and that had spatial and temporal characteristics. A review of approaches to work that inform HCI design suggests that activity-based approaches, which contextualize goals and actions in terms of both origins and personal investment, provide the minimum meaningful context required to accommodate concerns. Finally, we present an analysis of the implementation of medical guidelines in Britain that exemplifies the transformation in thinking required to design practically useful procedures: from models of work that emphasize control to those that emphasize commitment, and from conceptualizations of procedures as rationalizing and controlling to conceptualizations of procedures as educational. This analysis features the sensitivity to concerns in this particular case and draws some suggestive lines from what this case reveals about concerns to the kind of contributions a sensitivity to concerns would make to a contextual design process.

No abstract available.

Analyses of the costs and benefits of asynchronous communication, and the complementary properties of writing and speech, are used to predict that messages containing both writing and speech will be more communicative than either medium alone. Two experimental studies of asynchronous messaging are presented. Both experiments examine the use of pen-and-voice messages, that is voice messages attached to ‘scribbled’, i.e., uninterpreted text. The control conditions were voice messages alone, equivalent to an answerphone, and scribbled messages alone, equivalent to a fax. In Experiment 1 the visual component of the pen-and-voice messages was static, in Experiment 2 users could record short ‘movies’ including speech and pen movements over a document surface. Users showed a significant preference for the pen-and-voice messages in both experiments. In Experiment 2 half the number of pen-and-voice messages were required to achieve the same task performance as in the control conditions. It is concluded that dynamic pen-and-voice messages have considerable potential advantages over current single medium asynchronous communication facilities such as fax, answerphone, voicemail and e-mail.

In systems development it is essential for a piece of software to be able effectively to incorporate the requirements of the particular task domain that it is intended to address. This paper describes an approach that uses dialogue modelling to carry the requirements derived from task analysis through to the implementation phase of development. A notation based on production systems is used to develop an abstract specification of user and system behaviour which can subsequently be used as the basis for the implementation. The requirements for a computer-based tool are also discussed, with particular attention being given to ways in which the communication and reasoning about such a dialogue design can be supported.

The specification of a graphical user interface (GUI), like any other part of a computer system, is an incremental process whereby an outline of the system is systematically developed, evaluated, and revised until it is reasonably complete. This article describes some algorithms and procedures that can be used to automate the analysis of a specification to facilitate this iterative process. A propositional production system (PPS) is a notation that can be used by designers to describe the high-level behavior of a GUI. Such a description is executable and relatively easy to learn and use. PPSs are a form of state machine; therefore, much of the theory of state machines can be applied to their analysis. PPSs, however, provide the advantage of semiparallel definitions of state transitions. This is important, as dialogue models of modem GUIs allow a large number of simultaneously available inputs leading to very large state spaces. By dealing in sets of states, a PPS makes the problem of describing the potentially exponential number of state transitions tractable. This article discusses how this innovation can lead to efficient algorithms for analyzing a dialogue model for properties such as task completeness, reversibility of effect, accessibility, connectedness, and avoidance of deadlock.

There is a growing literature of experiments whose purpose is to compare different configurations for computer-mediated communication. If the results of these experiments are to be useful they must: ( i ) use the right experimental tasks; and ( ii ) measure the right dependent variables. This paper is concerned with the latter problem which is illustrated using data collected in experimental comparisons of three configurations of a text-based conferencing system. No significant differences were found using a measure of task outcome. This accords with numerous previous findings. However, a numberof process-related dependent variables were devised that did show significant effects. These included common ground, as measured by shared recall, and references to the topic of one message in the next available turn. Another, the use of first and second person pronouns in conversation approached significance. Finally, an approach to the selection of measures for use in studies of computer-mediated communication is commended.

This article is concerned with an analysis of the requirements for text-based on-line conferencing. From a system perspective, text-based on-line conferencing can be viewed as either message passing or data sharing. These complementary views give rise to different design dimensions. For example, the message-passing view is concerned with granularity, channels, message labels, and so on. The data-sharing view is concerned with the access different individuals have to the text: read only, appending, editing, pointing, and so on. A deliberately sparse prototype was built and placed in this design space. This minimal prototype has limited functionality so that the real problems experienced by users can show through. Relevant literature from disciplines such as social psychology, conversational analysis, and linguistics is briefly reviewed in terms of three generic communication tasks: synchronizing communication, maintaining structural coherence, and maintaining referents. An empirical analysis of subjects' use of the sparse prototype was analyzed to establish the relevance of the generic communication tasks to text-based on-line conferencing. Possible forms that support for these tasks might take are discussed.

An experiment was performed to examine predictions from Clark's contribution theory of discourse.Pairs were asked to use a text-based synchronous messaging system to solve a problem involving the layout of a bank.Contribution theory suggests that in such text-only communication common ground will be difficult to achieve.This was shown to be the case.A parallel system, where participants could use a common report space in addition to the messaging space, significantly reduced these probIems.The implications for design are discussed in terms of providing additional channels for communicating the results of discussion separate from the conversation itself.

Dissatisfaction with the traditional model of HCI research borrowed from experimental psychology has lead to a number of interesting new approaches. One is the so-called ‘hermeneutic approach’ based on field research methods. Another is to apply existing theory from cognitive psychology. This paper is mainly concerned with a third discernible approach based around a study of the artifacts or inventions built to facilitate human-computer interaction. The effectiveness of different system features is explained by reference to the user's task. The investigation of ‘observation-invention pairs’ is suggested as a way of providing generalisations about user behaviour consistent with this approach. The observation part is a statement about the behaviour of users with some specified generality. The invention serves to illustrate the observation's implications for design and provides a heuristic for further inventions. The paper relates observation-invention pairs to other analyses of artifacts and concludes that they have a place as general statements of knowledge for HCI design.

Staff in the Departments of Computer Science and Psychology at the University of York have been cooperating in interdisciplinary research since 1983. The mainstream of York's approach is to apply theory developed in these parent disciplines to HCI design. Our goal is to integrate formal and empirical methods. By formal methods we mean mathematical models that are capable of capturing properties of a user interface. By empirical methods we mean the observation and measurement of user behaviour. Integration of these two approaches is achieved by an iterative design process in which formal models are successively refined by testing their predictions against the results of user trials.

In most hypertext applications there will be occasions where the user knows the location of the information being sought because that location has been visited regularly in the past. This directed navigation can be distinguished from exploratory navigation where the user cannot specify precisely where the information might be within the hypertext system. Directed navigation can be facilitated by providing a personal browser which lists and gives direct access to frequently visited locations selected by the user. Different ways in which this could be implemented are discussed including facilities for automating the addition of new buttons to the personal browser. An appendix provides the code needed to program a demonstration within HyperCard. This monitors the number of times each card in the stack is visited and asks whether a button should be added after a card has been visited some criterion number of times.