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Refereed Journal Papers

Hornbæk, K. (2006), "Current Practice in Measuring Usability: Challenges to Usability Studies and Research", International Journal of Human-Computer Studies, Volume 64, Issue 2 , February 2006, Pages 79-102. [erlbaum] [abstract]

How to measure usability is an important question in HCI research and user interface evaluation. We review current practice in measuring usability by categorizing and discussing usability measures from 180 studies published in core HCI journals and proceedings. The discussion distinguish several problems with the measures, including whether they actually measure usability, if they cover usability broadly, how they are reasoned about, and if they meet recommendations on how to measure usability. In many studies, the choice of and reasoning about usability measures fall short of a valid and reliable account of usability as quality-in-use of the user interface being studied. Based on the review, we discuss challenges for studies of usability and for research into how to measure usability. The challenges are to distinguish and empirically compare subjective and objective measures of usability; to focus on developing and employing measures of learning and retention; to study long-term use and usability; to extend measures of satisfaction beyond post-use questionnaires; to validate and standardize the host of subjective satisfaction questionnaires used; to study correlations between usability measures as a means for validation; and to use both micro and macro tasks and corresponding measures of usability. In conclusion, we argue that increased attention to the problems identified and challenges discussed may strengthen studies of usability and usability research.

Hertzum, M. & Hornbæk, K. (2005) "TouchGrid: Touchpad pointing by recursively mapping taps to smaller display regions" Behavior & Information Technology, 24 (5), 337-346. [abstract]

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.

Hornbæk, K. & Frøkjær, E. (2004), "Usability Inspection by Metaphors of Human Thinking Compared to Heuristic Evaluation", International Journal of Human-Computer Interaction, 17(3), 357-374. [erlbaum] [pdf] [abstract]

A new usability inspection technique based on metaphors of human thinking (MOT) has been experimentally compared to heuristic evaluation (HE). The aim of MOT is to focus inspection on users’ mental activity and to make inspection easily applicable to different devices and use contexts. Building upon classical introspective psychology, MOT bases inspection on metaphors of habit formation, stream of thought, awareness and associations, the relation between utterances and thought, and knowing. An experiment was conducted in which 87 novices evaluated a large web application, and its key developer assessed the problems found. Compared to HE, MOT uncovered usability problems that were assessed as more severe on users and also appeared more complex to repair. The evaluators using HE found more cosmetic problems. The time spent learning and performing an evaluation with MOT was shorter. A discussion of strengths and weaknesses of MOT and HE is provided, which shows how MOT can be an effective alternative or supplement to HE.

Henriksen, K., Sporring, J., & Hornbæk, K. (2004), "Virtual Trackballs Revisited", IEEE Transactions on Computer Graphics and Visualization, 10 (2), 206-216, [see also] [ieee] [abstract]

Rotation of 3 dimensional objects by a 2 dimensional mouse is a typical task in applications such as computer aided design, operation simulations, and desktop virtual reality. The most commonly used rotation technique is a virtual trackball surrounding the object and operated by the mouse pointer. This article reviews and provides a mathematical foundation for virtual trackballs. The first but still popular virtual trackball was described by Chen et al. We show that the virtual trackball by Chen et al. does not rotate the object along the intended great circular arc on the virtual trackball, and we give a correction. Another popular virtual trackball is Shoemake's quaternion implementation, which we show to be a special case of the virtual trackball by Chen et al. Shoemake extends the scope of the virtual trackball to the full screen. Unfortunately, Shoemake's virtual trackball is inhomogeneous and discontinuous with consequences for usability. Finally, we review Bell's virtual trackball and review studies of the usability of virtual trackballs.

Hornbæk, K. & Frøkjær, E. (2003), "Reading Patterns and Usability in Visualizations of Electronic Documents", ACM Transactions on Computer-Human Interaction. 10 (2), 119-149, [acm] [pdf] [abstract]

We present an exploration of reading patterns and usability in information visualizations of electronic documents. Twenty subjects wrote essays and answered questions about scientific documents using an overview+detail, a fisheye, and a linear interface. We study reading patterns by progression maps, which visualize the progression of subjects' reading activity; and visibility maps, which show the duration different parts of the document are visible. The reading patterns help explain differences in usability between the interfaces. With the overview+detail interface, subjects get higher grades for their essays. All but one of the subjects prefer this interface. With the fisheye interface, subjects use more time on gaining an overview of the document and less time on understanding the details. Thus they read the documents faster, but display lower incidental learning. We also show how subjects have visible for a short period of time parts of the document not initially readable in the fisheye interface. This happen even though subjects express a lack of trust in the algorithm underlying the fisheye interface. When answering questions, the overview is used for directly jumping to answers in the document and to already-visited parts of the document. However, subjects are slower at answering questions with the overview+detail interface. From the visualizations of reading activity, we find that subjects using the overview+detail interface often explore the document further when a satisfactory answer has been found. Thus overviews may grab subjects' attention and possibly distract them.

Hornbæk, K., Bederson, B., & Plaisant, C. (2002), "Navigation Patterns and Usability of Zoomable User Interfaces with and without an overview" ACM Transactions on Computer-Human Interaction. 9 (4), 362-389, [acm] [pdf] [abstract]

The literature on information visualization establishes the usability of interfaces with an overview of the information space, but for zoomable user interfaces, results are mixed. We compare zoomable user interfaces with and without an overview to understand the navigation patterns and usability of these interfaces. Thirty-two subjects solved navigation and browsing tasks on two maps. We find no difference between interfaces in subjects' ability to solve tasks correctly. Eighty percent of the subjects prefer the interface with an overview, stating that it supports navigation and helps keep track of their position on the map. However, subjects are faster with the interface without an overview when using one of the two maps. We conjecture that this difference is due to the organization of that map in multiple levels, which renders the overview unnecessary by providing richer navigation cues through semantic zooming. The combination of that map and the interface without an overview also improves subjects' recall of objects on the map. Subjects who switched between the overview and the detail windows used more time, suggesting that integration of overview and detail windows adds complexity and requires additional mental and motor effort.

Refereed Conferences

Lunzer, A. & Hornbæk, K. (2006), "RecipeSheet: Creating, Combining and Controlling Information Processors ", to appear in ACM Symposium on User Interfaces and Software Technology (UIST 2006).

Hornbæk, K. & Frøkjær, E. (2006), "What Kinds of Usability-Problem Description Are Useful to Developers?" , to appear in HFES Annual Meeting 2006.

Nørgaard, M. & Hornbæk, K. (2006), "What Do Usability Evaluators Do in Practice? An Explorative Study of Think-Aloud Testing" , to appear in ACM Conference on Designing Interactive Systems (DIS 2006). [pdf] [abstract]

Think-aloud testing is a widely employed usability evaluation method, yet its use in practice is rarely studied. We report an explorative study of 14 think-aloud sessions, the audio recordings of which were examined in detail. The study shows that immediate analysis of observations made in the think-aloud sessions is done only sporadically, if at all. When testing, evaluators seem to seek confirmation of problems that they are already aware of. During testing, evaluators often ask users about their expectations and about hypothetical situations, rather than about experienced problems. In addition, evaluators learn much about the usability of the tested system but little about its utility. The study shows how practical realities rarely discussed in the literature on usability evaluation influence sessions. We discuss implications for usability researchers and professionals, including techniques for fast-paced analysis and tools for capturing observations during sessions.

Jakobsen, M. & Hornbæk, K. (2006), "Evaluating a Fisheye View of Source Code", to appear in Proceedings of the ACM Conference on Human Factors in Computing Systems (CHI 2006). [pdf] [plug-in] [abstract]

Navigating and understanding the source code of a program are highly challenging activities. This paper introduces a fisheye view of source code to a Java programming environment. The fisheye view aims to support a programmer’s navigation and understanding by displaying those parts of the source code that have the highest degree of interest given the current focus. An experiment was conducted which compared the usability of the fisheye view with a common, linear presentation of source code. Sixteen participants performed tasks significantly faster with the fisheye view, although results varied dependent on the task type. The participants generally preferred the interface with the fisheye view. We analyse participants’ interaction with the fisheye view and suggest how to improve its performance. In the calculation of the degree of interest, we suggest to emphasize those parts of the source code that are semantically related to the programmer’s current focus.

Frøkjær, E. & Hornbæk, K. (2005), "Cooperative Usability Testing: Complementing Usability Tests with User-Supported Interpretation Sessions", Extended Abstracts of ACM Conference on Human Factors in Computing Systems (CHI 2005), 1383-1386. [acm] [pdf] [abstract]

Recent criticism of think-aloud testing (TA) discusses discrepancies between theory and practice, the artificiality of the test situation, and inconsistencies in the evaluators' interpretation of the process. Rather than enforcing a more strict TA procedure, we describe Cooperative Usability Testing (CUT), where test users and evaluators join expertise to understand the usability problems of the application evaluated. CUT consists of two sessions. In the interaction session, the test user tries out the application to uncover potential usability problems while the evaluators mainly observe, e.g. as in TA or contextual inquiry. In the interpretation session, evaluators and test users discuss what they consider the most important usability problems, supported by a video of the interaction session. In an exploratory study comparing CUT to TA, seven evaluators find that interpretation sessions contribute important usability information compared to TA. Also test users found participation in the interpretation session interesting.

Hornbæk, K. & Frøkjær, E. (2005), "Comparing usability problems and redesign proposals as input to practical systems development", Proceedings of ACM Conference on Human Factors in Computing Systems (CHI 2005), 391-400. [acm] [pdf] [abstract]

Usability problems predicted by evaluation techniques are useful input to systems development; it is uncertain whether redesign proposals aimed at alleviating those problems are likewise useful. We present a study of how developers of a large web application assess usability problems and redesign proposals as input to their systems development. Problems and redesign proposals were generated by 43 evaluators using an inspection technique and think aloud testing. Developers assessed redesign proposals to have higher utility in their work than usability problems. In interviews they explained how redesign proposals gave them new ideas for tackling well known problems. Redesign proposals were also seen as constructive and concrete input. Few usability problems were new to developers, but the problems supported prioritizing ongoing development of the application and taking design decisions. No developers, however, wanted to receive only problems or redesigns. We suggest developing and using redesign proposals as an integral part of usability evaluation.

Fujima, J., Lunzer, A., Hornbæk, K. & Tanaka, Y. (2004), "Clip, Connect, Clone: Combining Application Elements to Build Custom Interfaces for Information Access", Proceedings of ACM Symposium on User Interfaces and Software Technology (UIST 2004), 175-184. [acm] [pdf] [video] [abstract]

Many applications provide a form-like interface for requesting information: the user fills in some fields, submits the form, and the application presents corresponding results. Such a procedure becomes burdensome if (1) the user must submit many different requests, for example in pursuing a trial-and-error search, (2) results from one application are to be used as inputs for another, requiring the user to transfer them by hand, or (3) the user wants to compare results, but only the results from one request can be seen at a time. We describe how users can reduce this burden by creating custom interfaces using three mechanisms: clipping of input and result elements from existing applications to form cells on a spreadsheet; connecting these cells using formulas, thus enabling result transfer between applications; and cloning cells so that multiple requests can be handled side by side. We demonstrate a prototype of these mechanisms, initially specialised for handling Web applications, and illustrate how it lets users build new applications that are tailored to their needs.

Hornbæk, K. & Frøkjær, E. (2004), "Two psychology-based usability inspection techniques studied in a diary experiment", 3rd Nordic Conference on Human-computer Interaction (Nordichi 2004), 3-12. [acm] [pdf] [abstract]

Inspection techniques are widely used during systems design as a supplement to empirical evaluations of usability. Psychology-based inspection techniques could give important insights into how thinking shapes interaction, yet most inspection techniques do not explicitly consider users' thinking. We present an experiment comparing two psychology-based inspection techniques, cognitive walkthrough (CW) and metaphors of human thinking (MOT). Twenty participants evaluated web sites for e-commerce while keeping diaries of insights and problems experienced with the techniques. Using MOT, participants identified 30% more usability problems and in a reference collection of problems achieved a broader coverage. Participants preferred using the metaphors, finding them broader in scope. An analysis of the diaries shows that participants find it hard to understand MOT, while CW limits the scope of their search for usability problems. Participants identified problems in many ways, not only through the techniques, reflecting large differences in individual working styles.

Fujima, J., Lunzer, A.,Hornbæk, K. & Tanaka, Y. (2004), "C3W: Clipping, Connecting and Cloning for the Web", The Thirteenth International World Wide Web Conference. [abstract]

Many of today's Web applications support just simple trial-anderror retrievals: supply one set of parameters, obtain one set of results. For a user who wants to examine a number of alternative retrievals, this form of interaction is inconvenient and frustrating. It can be hard work to keep finding and adjusting the parameterspecification widgets buried in a Web page, and to remember or record each result set. Moreover, when using diverse Web applications in combination — transferring result data from one into the parameters for another — the lack of an easy way to automate that transfer merely increases the frustration. Our solution is to integrate techniques for each of three key activities: clipping elements from Web pages to wrap an application; connecting wrapped applications using spreadsheet-like formulas; and cloning the interface elements so that several sets of parameters and results may be handled in parallel. We describe a prototype that implements this solution, showing how it enables rapid and flexible exploration of the resources accessible through user-chosen combinations of Web applications. Our aim in this work is to contribute to research on making optimal use of the wealth of information on the Web, by providing interaction techniques that address very practical needs.

Lunzer, A. & Hornbæk, K. (2004), "Usability Studies on a Visualisation for Parallel Display and Control of Alternative Scenarios", Proceedings of Conference on Advanced Visual Interfaces (AVI 2004), 125-132. [acm] [pdf] [abstract]

Many applications require comparison between alternative scenarios; most support it poorly. Subjunctive interfaces support the parallel setup, viewing and control of scenarios. We present experiments on a census-data browser, comparing a simple and a subjunctive interface. In the first experiment, subjects reported higher satisfaction and lower workload with the subjunctive interface, and relied less on interim marks on paper. Subjects also used fewer interface actions. However, we found no reduction in task completion time, mainly because some subjects encountered problems in using the facilities for setting up and controlling scenarios. Based on a detailed analysis of subjects' actions we redesigned the subjunctive interface to alleviate frequent problems, such as accidentally adjusting only one scenario when the intention was to adjust them all. At the end of a second, five-session experiment, users of this redesigned interface completed tasks 27% more quickly than with the simple interface.

Lunzer, A. & Hornbæk, K. (2003), "Side-By-Side Display and Control of Multiple Scenarios:Subjunctive Interfaces for Exploring Multi-Attribute Data", Proceedings of OzCHI 2003. [pdf] [abstract]

Information exploration often involves specifying alternative values for some set of parameters, and comparing the corresponding results. Some interfaces allow only one scenario, i.e., one set of parameter values, to be handled at a time. This means that to compare results the user must switch repeatedly among the scenarios of interest, and remember details of the results that have been seen. A subjunctive-interface approach may reduce this burden on the user. Subjunctive interfaces let users establish, view and adjust multiple scenarios in parallel, so that results can be compared side by side. As an illustration, we describe two subjunctive interfaces for comparing queries over a multi-attribute dataset. In both designs the query results are shown side by side, but in one case the input parameters' available values are laid out in menus, marked to show which queries use each value, while in the other the parameters are controlled by sliders, with the values that they take in the different queries displayed side by side like the results. Both designs appear to offer advantages over other exploration interfaces, because they reduce the number of interface actions required and the information that users must remember.

Hornbæk, K. & Frøkjær, E. (2003), "Metaphors of Human Thinking: a New Tool in User Interface Design and Evaluation", Proceedings of Interact 2003, 781-784. [pdf] [abstract]

Understanding human thinking is crucial in the design and evaluation of human-computer interaction. Inspired by introspective psychology, we present five metaphors of human thinking. The aim of the metaphors is to help designers consider important traits of human thinking. We illustrate how to use the metaphors for usability evaluation and how good and poor user interfaces can be appreciated in terms of the metaphors. An experiment with 87 subjects show that usability evaluation by metaphors of human thinking compared to heuristic evaluation uncovers usability problems that are assessed as more severe on users and more complex to repair.

Hornbæk, K. & Frøkjær, E. (2002), "Evaluating User Interfaces with Metaphors of Human Thinking", Proceedings of User Interfaces For All., also in Springer Lecture Notes in Computer Science, Vol. 2615, 486-507. [springer] [pdf] [abstract]

Inspection techniques are a useful tool for identifying potential usability problems and for integrating at an early stage evaluation with design processes. Most inspection techniques, however, do not consider users' thinking and may only be used for a limited range of devices and use contexts. We present an inspection technique based on five metaphors of essential aspects of human thinking. The aspects considered are habit; the stream of thought; aware-ness and associations; the relation between utterances and thought; and know-ing. The proposed inspection technique makes users' thinking the centre of evaluation and is readily applicable to new devices and non-traditional use contexts. Initial experience with the technique suggests that it is usable in discussing and evaluating user interfaces.

Frøkjær, E. & Hornbæk, K. (2002), "Metaphors of Human Thinking in HCI: Habit, Stream of Thought, Awareness, Utterance, and Knowing", Proceedings of HF2002/OzCHI2002. [pdf] [abstract]

Understanding human thinking is crucial in the design and evaluation of human-computer interaction. Inspired by introspective psychology, we present five metaphors of human thinking. The aim of the metaphors is to help designers to consider important traits of human thinking when designing. The metaphors capture aspects of human thinking virtually absent in recent years of HCI literature. As an example of the utility of the metaphors, we show how a selection of good and poor user interfaces can be appreciated in terms of the metaphors. The metaphors are also used to reinterpret central notions in human-computer interaction, such as consistency and information scent, in terms of human thinking. Further, we suggest the metaphors be used for evaluating interfaces.

Hornbæk, K. & Frøkjær, E. (2001), "Reading Electronic Documents: The Usability of Linear, Fisheye, and Overview+Detail Interfaces", CHI'2001, Proceedings of ACM Conference on Human Factors in Computing Systems, Seattle, WA, 31st March-5th April 2001, CHI Letters, 3(1), 293-300, [pdf] [acm] [abstract]

Reading of electronic documents is becoming increasingly important as more information is disseminated electronically. We present an experiment that compares the usability of a linear, a fisheye, and an overview+detail interface for electronic documents. Using these interfaces, 20 subjects wrote essays and answered questions about scientific documents. Essays written using the overview+detail interface received higher grades, while subjects using the fisheye interface read documents faster. However, subjects used more time to answer questions with the overview+detail interface. All but one subject preferred the overview+detail interface. The most common interface in practical use, the linear interface, is found to be inferior to the fisheye and overview+detail interfaces regarding most aspects of usability. We recommend using overview+detail interfaces for electronic documents, while fisheye interfaces mainly should be considered for time-critical tasks.

Frøkjær, E., Hertzum, M. & Hornbæk, K., (2000), "Measuring Usability: Are Effectiveness, Efficiency, and Satisfaction Really Correlated?", CHI'2000, Proceedings of ACM Conference on Human Factors in Computing Systems, the Haag, the Netherlands, 1st-6th April 2000, CHI Letters, 2(1), 345-352. [pdf] [acm] [abstract]

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.

Hornbæk, K. & Frøkjær, E. (1999), "Do Thematic Maps improve information retrieval?", in Sasse & Johnson (ed.), Proceedings of Human-Computer Interaction-INTERACT '99, IOS Press, Amsterdam: The Netherlands, 179-186. [abstract]

Thematic maps in the context of information retrieval are tools that graphically present documents and characterising terms. We investigated the usefulness of thematic maps in a laboratory experiment comparing a thematic map with a command language interface. Six subjects solved eight search tasks producing ten hours of logged and tape-recorded data. The experiment revealed no improvement in the quality of the documents retrieved when using a thematic map. A majority of the subjects considered the thematic map pleasant to use and thought that useful information was found on the map. However, searching took longer time using the thematic map compared with the boolean interface. Several subjects occasionally misinterpreted the structure and content of the map. The common expectation that thematic maps improve information retrieval lacks empirical underpinning and is in the present study only weakly confirmed.

Invited Journal Papers

Hornbæk, K. & Stage, J. (2006), “The Interplay between Usability Evaluation and User Interaction Design”, International Journal of Human-Computer Interaction, in press.

Hornbæk, K. & Frøkjær, E. (2004), "Research Alert for Reading Patterns and Usability in Visualizations of Electronic Documents", Interactions, January/February, 11-12. [acm]

Hornbæk, K., Bederson, B., & Plaisant, C. (2002), "Research alert for Navigation Patterns and Usability of Overview+Detail and Zoomable User Interfaces for Maps", Interactions, January/February, 11-12. [acm]

Hornbæk, K. (2002), "Menneske-datamaskine interaktion i informationssøgesystemer: evaluering af brugs- og læsevenlighed" Dansk Biblioteksarbejde, 63, 31-44. [pdf] [abstract]

Informationssøgesystemer siger mod at støtte mennesker i at søge efter, læse og på anden må de hå ndtere information. Ud fra min baggrund i fagfeltet menneske-datamaskine interaktion argumenterer jeg for at brugs- og læsevenlighed er nyttige evalueringskriterier for informationssøgesystemer. Denne argumentation er i overensstemmelse med en stigende interesse i fagfeltet informationssøgning for brugergrænseflader og for menneske-datamaskine interaktion. For at illustrere nytten af at fokusere på brugs- og læsevenlighed giver jeg to eksempler på evaluering af informationssøgesystemer som jeg har været med til at udvikle. Målet med brugergrænsefladerne til disse informationssøgesystemer er at støtte brugs- og læsevenlighed. Eksemplerne illustrerer hvordan vi i menneske-datamaskine interaktion arbejder med evaluering. De viser også hvordan tætte studier af interaktionen mellem mennesker og datamaskiner kan bruges til at forstå gode og då rlige egenskaber ved informationssøgesystemer.

Frøkjær, E., Perstrup, K. & Hornbæk, K. (1999), "Fagfolks dokumentationsarbejde og informationshå ndtering", Viden Om, April 1999, Særnummer om eksperimentelle søgemetoder, 15-19. [abstract]

Dansk BiblioteksCenter og Roskilde Universitetscenters laboratorium for intelligente systemer arrangerede den 29. januar 1999 en workshop om udvikling af edb-baserede søgeværktøjer og nye eksperimentelle søgemetoder. Vi var inviteret til at fortælle om hvad vi på DIKU arbejder med inden for det områ de. For læsere af Viden Om giver vi her et kortfattet resume. Først præsenterer vi den overordnede ramme for arbejdet. Dernæst fortæller vi om tre større eksperimentelle undersøgelser. Til slut omtaler vi nogle teorier, der har været ledende i arbejdet ved DIKU.

Book Chapters

Hornbæk, K., Bederson, B., & Plaisant, C. (2003), "Navigation Patterns and Usability of Overview+Detail and Zoomable User Interfaces for Maps", in Bederson & Shneiderman, The Craft of Information Visualization: Readings and Reflections, Morgan Kaufmann, 120-147.

Theses

Hornbæk, K. (2002), "Usability of Information Visualization: Reading and Interaction Processes", PhD Thesis, University of Copenhagen, DIKU Technical Report, 02/05, 110 pages. [pdf] [abstract]

The usability of information visualizations was investigated in empirical studies of information retrieval, map navigation, and reading of electronic documents. Overall, subjects prefer using interfaces with overviews. However, studies of the interaction processes show that subjects used mental and motor effort in switching to the overviews and that the overview occasionally distracted the subjects. For some tasks, subjects using overviews were therefore slower. Zoomable user interfaces were faster than interfaces with overviews when the maps navigated on were organized in multiple levels. Reading of electronic documents is crucial for information access and use, and we therefore aim at supporting that activity. An overview+detail interface for electronic documents improves the quality of essays that subjects write. Through visualizations of reading processes we describe how reading progresses and which parts of the documents subject attend to. Subjects used an overview-oriented reading style to read electronic documents presented by a fisheye interface. Sections that the fisheye algorithm treated as unimportant were visible for a shorter time than in the other interfaces, although subjects were uncomfortable in trusting the algorithm. In the studies described, different aspects of usability such as efficiency and effectiveness were not correlated. Consequently, we argue that usability studies should measure a range of usability aspects. Finally, human thinking as described in introspective psychology is used to clarify designs of human-computer interaction and is suggested as a focus for further research in information visualization.

Hornbæk, K. (1998), "Visualisering af Informationssøgning", MSc, 106 pages. [abstract]

Visualisering af informationssøgning er blevet foreslå et som en brugergrænsefladeteknik der effektivt kan støtte informationssøgning, og som kan afhjælpe mange af de problemer der opstå r ved brugen af traditionelle informationssøgesystemer. Visualisering af informationssøgning foregå r ved at udvide et edb-system der tillader søgning efter information, med grafisk præsentation af dokumenter, forespørgsler eller metainformation om systemets indhold. Dette speciale præsenterer et litteraturstudie af forskningsfeltet visualisering af informationssøgning, samt resultatet af en mindre empirisk undersøgelse af forskellen på søgning i et visuelt og et boolsk søgesystem. Litteraturen om visualisering af informationssøgning handler om hvordan man vælger data eller transformerer data til en form der er velegnet til at blive præsenteret grafisk, og om komplekse grafiske præsentationer der visualiserer store mængder data. Empiriske undersøgelser af hvordan informationssøgere bruger visuelle informationssøgesystemer, og særligt hvordan informationssøgeprocessen ændres ved brug af grafiske repræsentationer, er kun rapporteret i litteraturen i beskedent omfang. Nødvendigheden af yderligere empiriske studier bestyrkes af litteraturens mange uunderbyggede antagelser og den mangelfulde indsigt i hvordan mennesker anvender visuelle søgesystemer. For at undersøge forskellen i søgeprocessen og forskelle i søgeresultater i et ikke-grafisk og et grafisk informationssøgesystem, blev der gennemført et sammenlignende studium af et boolsk søgesystem og et visuelt søgesystem, baseret på multidimensional skalering. Dokumentsamlingen i det eksperimentelle system var fra konferencer og tidskrifter om menneske-datamaskine interaktion. Seks personer med domænekendskab gennemførte ialt 48 opgaver i løbet af ialt ti timers søgning i de to systemer. Der var ingen signifikant forskel på løsningernes kvalitet i det visuelle og det boolske søgesystem, og opgaverne blev gennemført på signifikant kortere tid i det boolske søgesystem. Flere af de almindelige antagelser om visuelle søgesystemers fordele der blev fundet i litteraturstudiet, må genovervejes i lyset af eksperimentets resultater. Søgeprocessen i de to systemer var forskellig. I det visuelle søgesystem var der signifikant flere skift mellem forskellige interaktionsformer, ligesom skimning af den grafiske præsentation ofte blev brugt som første søgeform. Den grafiske præsentation var vanskelig at forstå for brugerne og blev ofte fortolket uforudsigeligt. Hovedparten af forsøgspersonerne foretrak dog det grafiske system og fandt oversigten over dokumentsamlingen præsenteret i det grafiske system nyttig. Eksperimentet understregede at der er store individuelle forskelle i informationssøgning; de kvantificerbare aspekter af søgeprocessen og søgeresultatet varierer med op til en faktor fire mellem forskellige forsøgspersoner.

Other Publications

Lunzer, A. and Hornbaek, K. (2005) “An Enhanced Spreadsheet Supporting Calculation-Structure Variants, and its Application to Web-Based Processing.” In K.-P. Jantke, A. Lunzer, N. Spyratos and Y. Tanaka (eds.) Proceedings of the Dagstuhl Workshop on Federation over the Web (Lecture Notes in Artificial Intelligence, Vol. 3847), Dagstuhl Castle, Germany, 143-158.

Als, B., Frøkjær, E., Hornbæk, K., Høegh, R., Jensen, J., Nørgaard, M., Skov, M., Stage, J. & Uldall-Espersen, T. (2005) “The USE Project: Bridging the Gap between Usability Evaluation and Software Development”, Proceedings of Fifth Danish HCI Research Symposium , 110-114. November 8 2005, Copenhagen Business School.

Frøkjær, E. & Hornbæk, K. (2004) "Studying usability evaluation to improve its practical utility", Proceedings of Fourth Danish HCI Research Symposium, November 16, Aalborg University. [pdf]

Frøkjær, E. & Hornbæk, K. (2004) "Input from usability evaluation in the form of problems and redesigns: results from interviews with developers", in Proceedings of Workshop on Improving the Interplay between Usability Evaluation and User Interface Design, Nordichi 2004, October 24, Tampere, Finland. [pdf]

Frøkjær, E. & Hornbæk, K. (2003), "The metaphors-of-human-thinking technique for usability evaluation compared to heuristic evaluation and cognitive walkthrough", Proceedings of the Third Danish HCI Research Symposium. [pdf]

Lunzer, A. & Hornbæk, K. (2003), "Subjunctive interfaces: visualisations for parallel display and control of alternative scenarios", Proceedings of the Third Danish HCI Research Symposium. [pdf]

Lunzer, A. & Hornbæk, K. (2003), "Widget multiplexers for side-by-side display and control of information-processing scenarios", HCI International 2003. [pdf]

Frøkjær, E. & Hornbæk, K. (2002), "Studying the Utility of Metaphors of Human Thinking in HCI", Proceedings of 2nd Danish Research Symposium on HCI, DIKU Technical Report, 2002/19, [pdf]

Hornbæk, K., Engberg, D. T., & Gomme, J. (2002), "Video Lectures: HCI and e-learning challenges", in Workshop on Human-computer interaction and E-learning, NORDICHI 2002, [pdf]

Henriksen, K, Sporring, J., Hornbæk, K (2002), "Virtual Trackballs Revisited", Proceedings of DSAGM'2002. [pdf]

Hornbæk, K. (2001), "Information Visualizations of Electronic Documents: Usability and Reading Patterns", 1st Danish Research Symposium on HCI, [pdf]

Hornbæk, K., Bederson, B., & Plaisant, C. (2001), "Navigation Patterns and Usability of Overview+Detail and Zoomable User Interfaces for Maps", Technical Report # 2001-11, HCIL, University of Maryland, 26 pages. [pdf] [html]