The Evolution of HCI

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The Evolution of Human-Computer Interaction

John M. Carroll

Cap. I del LibroHuman-Computer Interaction in the New Millennium

The Emergence of Usability

Human-Computer Interaction (HCI) is the study and the practice of usability. It is aboutunderstanding and creating software and other technology that people will want to use, will be ableto use, and will find effective when used. The concept of usability, and the methods and tools toencourage it, achieve it, and measure it are now touchstones in the culture of computing.

Through the past two decades, HCI emerged as a focal area of both computer science research anddevelopment and of applied social and behavioral science. Some of the reasons for its success arestraightforwardly technical: HCI evoked many difficult problems and elegant solutions in the recenthistory of computingfor example, in work on direct manipulation interfaces, user interfacemanagement systems, task-oriented help and instruction, and computer-supported collaborativework. Other reasons are broadly cultural: The province of HCI is the view the nonspecialist public has

of computer and information technology and the impact that technology has on their lives in thesense that it is the visible part of computer science and technology. The most recent reasons arecommercial: As the underlying technologies of computing become commodities, inscribed on genericchips, the noncommodity value of computer products and services resides in applications and userinterfacesthat is, in HCI.

The beginning of HCI is sometimes traced to the March 1982 (U.S.) National Bureau of Standardsconference, "Human Factors in Computer Systems," though related conferences and workshops wereconducted throughout the world at about that time. It is surely true that after the Bureau ofStandards conference, HCI experienced meteoric growth. However, fourlargely independentthreads of technical development from the 1960s and 1970s provided the foundation that allowedthis interdisciplinary program to gel so rapidly in the early 1980s.

These four threads were prototyping and iterative development from software engineering; software

psychology and human factors of computing systems; user interface software from computergraphics; and models, theories, and frameworks from cognitive science. It is interesting to rememberthese four roots of HCI, since the concerns that evoked them and that brought them together are stillunderlying forces in HCI today.

Prototyping and Iterative Development

In the 1960s, advances in computer hardware enabled new applications requiring software systemsof far greater scale and complexity than before. But these greater possibilities exacerbated problemsof software development: cost overruns, late delivery, and ineffective and unreliable systems thatwere difficult to maintain. This was termed the "software crisis." It led to the emergence of softwareengineering as a professional discipline.

The software crisis was never resolved per se. Rather, it helped to establish design and developmentmethods as a central topic in computing. Early approaches emphasized structured decomposition andrepresentation of requirements and specifications, and a disciplined workflow of stages and hand-offscalled the "waterfall." Indeed, this was part of a broad movement toward more formal designmethods during the 1960s (Jones 1970).

However, empirical studies of the design process and practical experience in system developmentraised questions about the new design methods. A prominent case was Brooks's (1975/1995)analysis of the development of the IBM 360 Operating System, one of the largest and mostscrupulously planned software design projects of its era. Brooks, the project manager, observed that


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critical requirements often emerge during system development and cannot be anticipated. Heconcluded that software designers should always "plan to throw one away."

This was a striking lesson and one that continues to inspire studies of design. Design is now seen asopportunistic, concrete, and necessarily iterative. Designers typically work toward partial solutions forsubsets of requirements, using prototypes to evoke further requirements and, indeed, to reformulatethe goals and constraints of the problem. By providing techniques to quickly construct, evaluate, and

change partial solutions, prototyping has become a fulcrum for system development.

Software Psychology and Human Factors

The software crisis intensified interest in programming as a human activity. It heightened the needfor more programmers, for better-trained programmers, for more productive programmers. Thedevelopment of time sharing and interactive computing allowed new styles of programming andmade the dynamics of individual programmer activity more salient. Programming became recognizedas an area of psychology involving problem solving and symbol manipulation (Weinberg 1971).

Through the 1970s, a behavioral approach to understanding software design, programming, and theuse of interactive systems developed rapidly. This work addressed a wide assortment of questionsabout what people experience and how they perform when they interact with computers. It studied

how system response time affects productivity; how people specify and refine queries; how syntacticconstructions in programming languages are more or less difficult; and how aids like mnemonicvariable names, in-line program comments, and flowcharts support programming. By the end of thatdecade, a software psychology research community had formed (Shneiderman 1980).

This work inspired many industrial human factors groups to expand the scope of their responsibilitiestoward support for programming groups and the usability of software. During the latter 1970s,several extensive compilations of research-based guidelines appeared, and most computermanufacturers (there were no exclusively-software companies at that time) established usabilitylaboratories, whose scope of responsibility steadily expanded.

New User Interface Software

Before the 1960s, the notion of "user interface" was completely unarticulated. The focus ofcomputing was literally on computations, not on intelligibly presenting the results of computations.This is why the early visions of personal, desktop access to massive information stores (Bush 1945),graphical and gestural user interfaces (Sutherland 1963), and synchronous collaboration throughdirect pointing and shared windows (Engelbart and English 1968) are historically so significant.

Through the 1970s, advances in workstation computers and bit-mapped displays allowed these earlyvisions to be consolidated. A prominent example is work at the Xerox Palo Alto Research Center onthe Alto computer and the Smalltalk-72 environment. It is striking that the essential concepts ofdesktop computing that guided the next 20 years of research and development emerged during thisearly period.

Models, Theories, and Frameworks

During the latter 1970s, cognitive science had coalesced as a multidisciplinary project encompassinglinguistics, anthropology, philosophy, psychology, and computer science. One principle of cognitivescience was that an effective multidisciplinary science should be capable of supporting application toreal problems and to benefit from it. Many domains were investigated, including mechanics,radiology, and algebra. HCI became one the original cognitive science domains.

The initial vision of HCI as applied science was to bring cognitive science methods and theories tobear on software development. Most ambitiously, it was hoped that cognitive science theory couldprovide substantive guidance at very early stages of the software development process. This


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guidance would come from general principles of perception and motor activity, problem-solving andlanguage, communication and group behavior, and so on. It would also include developing a domaintheory, or theories, of HCI.

A prominent early example was the Goals, Operators, Methods, and Selection (GOMS) rules modelfor analyzing routine human-computer interactions (Card, Moran, and Newell 1983). This was anadvance on prior human factors modeling, which did not address the cognitive structures underlying

manifest behavior. But it was also an advance on the cognitive psychology of the time: It explicitlyintegrated many components of skilled performance to produce predictions about real tasks. TheGOMS model is important because it set a standard for scientific and theoretical rigor and innovationthat became a defining characteristic of HCI.

The foundations of HCI remain an active focus of research. The first group of papers in this volumeshows how these foundations are continuing to expand the disciplinary scope and relevance of HCImodels, theories, and frameworks to practitioners.

User-Centered System Development

These four starting points converged in the early 1980s through organizational initiatives includingACM's Special Interest Group in Computer-Human Interaction (SIGCHI) and IFIP's Task Group onHuman-Computer Interaction (later, Technical Committee 13). Initially, HCI had two foci, methodsand software, and a major theme was the integration of the two in a framework called user-centeredsystem development.

The methods focus was on techniques to achieve better usability. This entailed explicating theconcept of usability with respect to learning, skilled performance, and subjective experiences, likesatisfaction and fun. It involved the development and empirical validation of models and theories. Itinvolved laboratory studies of people learning and using systems, and of techniques for evaluatingsystems. And it involved working within development organizations to understand how to involveusability professionals earlier and more effectively in software development. The methods focusbecame known as usability engineering.

The software focus of HCI was concerned with inventing and refining graphical user interfaceconcepts and techniques to make systems more powerful, more useful, and more usable. Animportant consequent objective was to make new user interface concepts and techniques easier fordevelopers to employ. This entailed the development of toolkits and software frameworks. Thesoftware focus became known as user interface software and tools.

The method and software foci often cross-leverage one another. For example, new user interfacemetaphors are developed from theory and from user studies, refined and implemented in prototypesystems, evaluated in further user studies, and then incorporated into toolkits. Through the past twodecades, these original focus areas have continued to expand and diversify, though their synergisticrelationship remains a cornerstone of HCI. Other focal areas have developed, such asgroupware/cooperative activity and media/information.

Usability Engineering Methods and Concepts

The early focus of usability engineering was evaluation: gauging the success of implementedsoftware and systems with respect to measurable criteria. It was patterned on the laboratory-oriented human factors paradigm in telecommunications. However, the ascendance of prototypingand iterative development in software and the ambition of engaging cognitive science as a foundationfor human-computer interaction pushed the focus of evaluation work upstream in the systemdevelopment process.

Prototyping and iterative development place a high premium on formative, rather than summative,evaluation (Scriven 1967)that is, on evaluation that is carried out within the development processand that can guide redesign, rather than merely gauge attributes of a design result. Formativeevaluation methods are often qualitative; a typical method involves having people "think aloud" as


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they perform a task. Theory-based models and tools took an even more ambitious position, seekingto enable analytic evaluations of designs before they were implemented even as prototypes. Usabilityengineering has remained a core concern of the ACM SIGCHI community, and its CHI Conference,but subcommunities have also developed for usability methods (the Usability Professional'sAssociation) and for theory-based models (the Conference on User Modeling).

The objective of providing guidance earlier in the system development process entrained

fundamental changes in usability engineering. An example is the recognition that the earliest pointfor impact is requirements analysis. The sociologists and anthropologists who had come to HCIthrough its connection to cognitive science showed through field studies of work practices that peopledo their work and use their tools in surprisingly creative ways (Suchman 1987). But their workpractices are often not easy to anticipate without direct study or direct user participation in thedevelopment process. A subcommunity addressing these themes has formed around the ParticipatoryDesign Conference and the ACM Conference on Computer-Supported Cooperative Work (CSCW).

A second example is the growing focus on design methods: Usability can be designed as well asevaluated, but a design-time usability process entails coordination with graphical and interactiondesigners that is still just beginning. This design thread has led to another subcommunity formedaround the ACM Symposium on Designing Interactive Systems (DIS), a conference series started in1995.

Complementary to moving usability work further upstream in design and development is a focus inusability engineering on cost-benefit tradeoffs in methods (Bias and Mayhew 1994). The mostevident manifestation of this theme has been widespread effort at developing "low-cost" inspectionand walkthrough methods. But cost-benefit is a complex issue. Different methods have differentgoals, producing different types of benefits. Some continuing questions for usability engineering arehow methods can leverage foundations in science and theory; how methods can be evaluated; andhow different types of methods, like laboratory studies, field studies, walkthroughs, and analyticmodels, can be integrated with one another and with other methods and processes of systemdevelopment.

The second group of papers in this volume shows how usability engineering is developing. It isaddressing an ever-greater variety of types of systems and usability phenomena, such as workeradaptation. It is developing new approaches, such as the integration of user interface managementsystems with cognitive models. But it is also focusing on better consolidation and utilization of results

and concepts in hand.

User Interface Software and Tools

User interface software and tools is concerned with user interface concepts and metaphors, displayand interaction techniques, and software development methods. This is surely the most visiblysuccessful area of HCI. The user interfaces that more or less everyone encounters more or less everydaythe mouse and bitmap display, the desktop metaphor and window management, displaywidgets like scroll-bars, menus, and dialog boxesemerge from this research and developmentwork. This area is a distinct professional subcommunity within HCI, with its own ACM conference,User Interface Software and Tools, since 1987.

A continuing research thread in this area is architectures for user interface software. An early

objective was separation of the user interface and application functionality into distinct layers. Thisapproach modularized the user interface in user interface management systems, encouragingiterative redesign (for example, Tanner and Buxton 1985). However, layering entrained limitations onthe granularity of user interface interactions. It also proved to be an obstacle to incrementaldevelopment methods, because it presupposed top-down decomposition with respect to what wasuser interface and what was application functionality. Current approaches favor developing userinterfaces and functionality in the same language, either in new languages invented for this purpose,like Visual Basic, or through extensions to standard languages for implementing functionality, such aslibraries and toolkits for C++ or Java.


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A key goal in this area has always been to ease the development of interactive systems. Throughtime, this goal has become more challenging because the skills of application developers havebecome more diverse. For example, this motivated a family of prototyping tools based on thepremise that user interface software could be directly created "by demonstration."

The third group of papers summarizes the progress to date in user interface software and tools andidentifies some of the key challenges for the future. The key questions for user interface software

and tools are what models and techniques will be most appropriate for creating interfaces withcontrols and displays quite different from those of the graphical user interface paradigm of the past20 years. For example, what are suitable architectures and tools for interfaces with voice, gesture, orposition-sensing controls and immersive or wearable displays?

Groupware and Cooperative Activity

The early vision that interactive computing would enable human collaboration was already borne outin the 1970s by ARPA Net e-mail and Usenet newsgroups. Before HCI even existed, there had beenconsiderable research on teleconferencing and other networked collaboration (Hiltz and Turoff1978/1993). In the 1980s, possibilities for computer-supported cooperative work (CSCW), as well asthe scope human-oriented issues considered, became more diverse. E-mail became a universalcommunication tool. Videoconferencing, electronic meeting rooms, and workflow support systems

became common. Several very visible experiments with media spaces and shared virtualenvironments were carried out. Through the 1990s, networked collaboration became richer and moreaccessiblefor example, through the World Wide Web.

CSCW, as a subcommunity in HCI, formed around the ACM CSCW Conference series starting in 1986.At first, the focus was on collaborative systems (groupware) and human-computer interactions withcollaborative systems. But the more significant impact of CSCW, one that goes beyond theconference, is the recognition that all systems are used in a social context. In this sense, CSCW hasbecome more a view of HCI than a subcommunity with it. CSCW has served as a conduit for theexpansion of the science foundation of HCI to incorporate activity theory, ethnomethodology, andconversation analysis, among others.

Studies of work practices and of technology in the workplace have radically altered the scope of HCIconcerns. Subtle features in the organization of work are often critical but easily missed in standard

requirements processes. Some of the powerful features may be idiosyncratic to a particular type ofwork context, such as air traffic control rooms, or even to individual workplaces and groups. Evenwhen technology appropriately addresses workplace needs, adopting new technology ineluctablydisrupts work, at least temporarily. The effects of technology are not uniform across an organization;some workers benefit, but others may lose. And technology can be a double-edged sword: Makingsomeone's work easier reduces the skill required to perform the work. In a given organizationalcontext, it may reduce status, pay, and even job security.

Much of the focus of CSCW continues to be on new groupware systems. In the past decade, thisthrust of CSCW has emphasized Internet systems. For example, there are many current reworkingsof the classic multi-user domain (MUD) paradigm but bundling suites of communication tools, such aschats, multi-user whiteboards, videoconferencing, and shared applications, with graphical Web-clients.

Recently, work on groupware systems and cooperative activity has converged around the concept of"community." Examples of communities are varied, including dispersed groups of collaboratingscientists, people subscribed to given newsgroups or other online services, and towns orneighborhoods with local networking infrastructures. On the one hand, this work investigates how avariety of interactions can be coherently supported to foster the qualities of community inparticipants. On the other hand, it investigates the social and psychosocial consequences ofparticipation in such communities.

The fourth group of papers in this volume examines the history, current approaches, and challengesof groupware and cooperative activity.


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Media and Information

In the early 1980s, possibilities for media other than formatted text were quite limited. Toward theend of the 1980s, this had changed dramatically: Hypertext was everywhere. In 1987, Apple beganincluding HyperCard with all of its personal computers. At the same time, standard image formatswere making it easier to create and share graphics and visualizations. Relatively good quality

synthetic speech became available on personal computers. In the 1990s, these trends accelerated:The World Wide Web made hypertext a standard information design, Web-pages and single-click e-mail attachments made sharing images as easy as sharing text, and surprisingly good speechrecognition became available on personal computers.

Where CSCW was initially a subcommunity of HCI that ended up providing a new perspective on whatHCI is about, multimedia and hypermedia were initially a small collection of enhancements to userinterface presentations but have continued to develop and diversify to produce half a dozen newsubareas of HCI. Each of these areas is redefining the scope of HCI. Some examples are digitallibraries, visualization and virtual environments, spoken-language interfaces, and agent-based andrecommender systems.

The World Wide Web is a vast collection of information, but it is not a library. Finding things in theWeb may be hit or miss, but it has helped to focus research and development interest on the human

aspects of building and accessing large hypertext databases. Digital libraries were originallyconceived of as an integration of database systems, multimedia, and information retrieval. However,the rapid growth of interest in digital libraries and the consequent need to make them accessible to awider range of people has transformed digital libraries into a subarea of HCI as well.

Graphics and visualization techniques were central to the development of the contemporary userinterface paradigm. However, continuing advances in hardware speed and other underlyingtechnologies now allow large-scale graphical animations. Users do not merely display and inspectstatic visualizations; they can view animated sequences of visualizations and navigate throughvisualized spaces. In a limiting case, users are surrounded by wall-sized displays, viewed throughdepth-enhancing goggles, perceptually immersed in their data.

Twenty years ago, sound in the user interface meant warning beeps. Sound got attention incircumstances where flashing text boxes sometimes did not. During the 1980s, HCI incorporated a

wider range of nonspeech sounds into the user interface (sometimes called "earcons") and madeprogress enhancing the quality of synthetic speech and applying it in telephone-based informationsystems. More recently, advances in speech recognition and natural language processing, and inunderlying hardware and software technologies, have allowed remarkable progress in speech input,particularly in dictation applications.

Artificial intelligence has always played a role in HCI. Intelligent help and tutoring systems have beenheavily researched through the past two decades. One of the obstacles to widely deploying suchtechniques in user interfaces is the amount of knowledge engineering required. This is one reasonthat intelligent tutoring systems tend to be developed for relatively closed domains of knowledge, likeelementary mathematics. More recent approaches are exploring self-organizing agents andrecommendation systems that aggregate the decisions and actions of many people to provideinformation resources.

The hypertext conference has continued, but the digital library community now has its own ACMconference series. There is also an ACM conference on multimedia. The fifth group of papers in thisvolume presents a diverse view of ongoing work in this area. It seems this "subarea" of HCI isalready too rich and too diverse to cohere. In the new millennium, media and information will surelybecome several distinct areas. For example, the sixth group of papers addresses the integration ofcomputation with real environments, a focus that has become distinctive only recently and promisesto be become far more important in the future.

The last group, "HCI and Society," includes discussions of challenges and possibilities for education,community-building, and the development of social capital more generally, as facilitated, or at least


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modulated, by information technology. In the new millennium these considerations may yet becomemainstream as foundations for HCI and as criteria for usability engineering methods.

Toward the New Millennium

At the inception of HCI, the notion that computer systems and software should be designed anddeveloped with explicit consideration of the needs, abilities, and preferences of their ultimate userswas not a dominant view. Most writings about computing from the mid-1970s are stunninglydismissive of usability and rather patronizing of users. After only a decade, the computer industryand the discipline of computer science were transformed. The case had been made for a user-centered system development process, a process in which usability was a primary goal. People beganto distinguish sharply between technology-driven exploratory development, which is now oftenaccompanied by explicit disclaimers about usability, and real system development, in whichempirically verified usability is the final arbiter.

With the advent of the 1990s, HCI research had become relatively well integrated in computerscience. A 1988 Association for Computing Machinery (ACM) task force enumerated HCI as one ofnine core areas of the computer science discipline (Denning et al. 1989). A joint curriculum task forceof the ACM and the IEEE (Institute of Electrical and Electronic Engineers) recommended the inclusionof HCI as a common requirement in computer science programs (Tucker and Turner 1991). And HCIwas included as one of ten major sections of the first Handbook of Computer Science andEngineering (Tucker 1997). In the 1990s, computer science students and the corporations that hirethem demanded HCI courses in university curricula. Several major computer science departmentshave designated HCI as a research focus, and several comprehensive undergraduate texts haveappeared.

In the computing industry, HCI practitioners have become well integrated in system development.HCI specialists have moved into a great variety of roles beyond human factors assurance. They havebeen routinely included in customer/user interactions to understand the need for new products,product planning and specification; in the development and evaluation of prototypes and systems; inthe design of documentation and training; and in installation and user support. There has been anobvious trend for HCI specialists to be promoted into project management.

HCI remains an emerging area in computer science. Its four roots from the 1960s and 1970ssoftware engineering, software human factors, computer graphics, and cognitive sciencehavegrown and intertwined. New influences and strands have been incorporatedbroader social science,networking, media, information management, and artificial intelligence. HCI has become the focusfor a new view of what computing is about. The future promises to be far more exciting than thequite exciting recent past. HCI only existed for the final quarter-century of the second millenniumtime enough to irrevocably shake up the discipline of computer science and the trajectory ofcomputing technology, but not a lot of time. HCI in the new millennium gives us much to lookforward to.

Acknowledgment

This is a much revised and broadened descendant of a survey paper that appeared inAnnual Reviewof Psychology,Volume 48, Palo Alto, CA: Annual Reviews, 1997, pages 501522. That earlier versiondevelops some of the points here in more detail and with more complete citations. I am grateful to

Andrew Dillon, Brad Myers, Sharon Oviatt, Ben Shneiderman, Alistair Sutcliffe, Terry Winograd, andan anonymous reviewer for guidance, discussion, and comments on this essay.

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