Publications by topic

Last modified date: 2004/01/01 - Some Pdf files are available here. If you are interested in any other paper, please e-mail me. You need Acrobat(r) Reader, available at no charge on Adobe's web site.

De Angeli, A., Rollo Carpenter. Stupid computer! Abuse and social identities.

Pdf Abstract This paper presents a preliminary analysis of verbal abuse in spontaneous human-chatterbot conversations. An ethnographic study suggested that abuse is pervasive and may reflect an asymmetrical power distribution, where the user is the master, and the chatterbot the slave. We propose that verbal aggression in this setting may be a social norm applied by users to differentiate themselves from the machine in what can be regarded as a form of interspecies conflict. The findings stress the importance of naturalistic, ethnographic studies to uncover social dynamics of virtual relationships.

De Angeli, A. (2005). To the rescue of a lost identity: Social perception in human-chatterbot interaction.AISB'05 Proceedings of the joint symposium on Virtual Agents Symposium, 7-14.

Pdf Abstract Imagine a future world where humans and machines will be involved in joint activities requiring social skills. This paper presents an overview of the dawnings of this world, concentrating on chatterbots - computer programs which engage the user in written conversation - and their users . Driving upon Clark's theory of Language and the psychological theory of self-categorisation by Turner, it presents an analysis of social reactions to chatterbots and a taxonomy of the technology. The basic assumption of the paper is that chatterbots are special entities which offer new ways of being and relating to others. The action of talking to a machine leads to the affordance in the user, and to the projection in the chatterbots, of new social identities. These identities are the drivers of the interaction and fundamental determinants of social presence. Keywords: Common ground, self-categorisation, stereotypes, anthropomorphism.

Briggs, P., Burford, B., De Angeli, A. (2004). Personalisation and trust: a reciprocal relationship? In K. Karat, J.O. Blom, and Karat J. (Eds.), Designing personalised user experiences in e-commerce, (pp. 39-55). Norwell, MA, USA: Kluwer Academic Publishers.

Pdf Abstract Trust and personalisation are related constructs. Trust is generally accepted as a prerequisite for good personalisation practice. Customers are not likely to reveal confidential information about themselves to an untrustworthy party, and they may be suspicious of data harvesting practices if they feel the information may be misused in some way. But the converse relationship might also hold: good personalisation practice may be a pre-requisite for trust building online. At present, relatively few studies of trust suggest an important role for personalisation in the formation of trust, but we argue below that personalisation may play a larger role than that suggested by the current trust literature. Following a critical review of online trust studies, we suggest that personalisation is important for the development of trust in long-term relationships between consumer and online vendor, but argue that its role in short-term interactions is unclear. We then present a study that explores the extent to which people may be influenced by the promise of a personalised transaction, in order to clarify the influence of personalised practices on initial trust judgments. Most researchers agree that trust is a vital construct for e-commerce. It has been argued that in order to develop a successful e-commerce business: The factors that produce a sense of trustworthiness need to be identified, in their entirety. Their interactions need to be understood, and their relative importance determined. Unfortunately researchers also agree that trust is an extremely difficult construct to work with, since it takes its meaning, chameleon-like from the context in which it operates. Thus trust is defined differently within the different fields of philosophy, sociology, psychology, management, political science and most recently human computer interaction. Furthermore, different manifestations of trust have been observed within any one field each with antecedents and consequences particular....

De Angeli, A. and Johnson, G.I. (2004). Emotional intelligence in interactive systems. In D. McDonagh, P. Hekkert, J. van Erp and D. Gyi (Eds.), Design and Emotion, (pp.262-266) London: Taylor & Francis.

Pdf Abstract In this paper, we introduce the Emotional Intelligence Framework, EIF (Salovey et al., 2000) in order to evaluate the state of the art of emotionally adept technology. Our belief is that the EIF can usefully guide further development of affective computing, as it encompasses more than a focus upon superficial sensor-level interaction. Keywords: human-computer interaction, affective computing.

Briggs, P., Simpson, B. and De Angeli, A. (2003). Does personalisation affect trust in online advice? CHI2003 Workshop Designing Personalized User Experiences for eCommerce: Theory, Methods, and Research, April 5-10, 2003, Fort Lauderdale, Florida.

Pdf Abstract This report describes an experimental investigation of two factors which are believed to influence users trust and willingness to engage in online commerce. The factors are: (a) reputation (a factor related to brand), and (b) personalisation. One hundred and seven users were logged on to a mock travel insurance website and asked to fill in insurance forms online, to make a decision as to whether or not they wanted to purchase insurance and then to answer a follow-up questionnaire. Behavioural and subjective measures of trust in the site were taken. Personalisation was shown to favourably influence user judgments about the site, although not to direcly influence trust. Keywords: Trust, personalisation, advice, Internet, e-commerce.

Briggs, P., Burford, B., De Angeli, A. and Lynch, P. (2002). Trust in Online Advice. Social Science Computer Review, 20 (3), 321-332.

Pdf Abstract Many people are now influenced by information and advice they find on the Internet. Some of that information may be sound advice but much of it is of dubious quality. This paper describes two studies concerned with those factors influencing people's responses to online advice. The first study is a qualitative account of a group of house-hunters attempting to find worthwhile information online. The second describes a survey of over two and a half thousand people who had actively sought advice over the Internet. A framework for understanding trust in online advice is proposed in which first impressions are distinguished from more detailed evaluations. Good web design can influence the first process, but three key factors - source credibility, advice personalisation and predictability - are shown to determine whether or not people actually follow the advice given. Keywords: Trust, persuasion, advice, Internet, e-commerce, consumer research, HCI.

Brigg, P., Burford B. and De Angeli, A. (2002). Who do you turn to? Predicting trust in online advice. CHI2002 Workshop on The Philosophy and Design of Socially Adept Technologies.

Pdf Abstract Many people people are now influenced by the information and advice they find on the Internet, much of it of dubious quality. This paper is concerned with those factors capable of influencing people's response to online advice. It describes a survey of over two and a half thousand people who had actively sought advice over the Internet. A framework for understanding trust in online advice is proposed in which three key factors - source credibility, personalisation and predictability - are shown to predict whether or not people actually follow advice given online. Keywords: Trust, persuasion, advice, Internet, e-commerce.

De Angeli, A., Lynch, P. and Johnson, G.I. (2002). Pleasure vs. efficiency in user interfaces: Towards an involvement framework. In W.S. Green and P.W. Jordan (Eds.), Pleasure with products: Beyond usability, (Chapter 7, pp. 97-111) London: Taylor & Francis.

Pdf Abstract The concept of usability is regarded by many as a milestone in the history of computer system design, specifically the design and evaluation of user interfaces. Since the term entered common usage in the early 1980's, the consideration of usability has greatly impacted the way in which many interactive systems are developed. Usability compels designers to think about end-users from the very beginning. Therefore, it has contributed to the evolution from the traditional topdown design approach (all requirements were specified in the planning phase and then developed by stepwise refinements) to a more iterative-design approach (evaluation and implementation are closely linked, user input at key stages, and ongoing requirements definition and system specification). Despite the apparent current popularity of usability thinking, the acceptance of the user-centred metric has not been easy in a development world dominated by a previously unquestioned systemcentred philosophy. Historically, the latter approach as sumed that users could, and would, adapt to whatever was built. Training, support documentation and 'Help' functions were considered to be the most appropriate solution to serious interaction difficulties. Only within the usability framework, has the end-user become the focus of the design process. The recognition that usability is a fundamental aspect of product quality as well as of marketing is a fairly recent reality. Nowadays, much usability research effort is devoted to the development and validation of costeffective evaluation tools to encourage the integration of usability issues into design (e.g. Nielsen, 1993; Johnson, 1996; Jordan, Thomas, Weerdmeester and McClelland, 1996; De Angeli, Natera, Costabile, Garzotto and Paolini, 2000). Currently, the value of the usability framework is so well acknowledged (ISO, 1991) that proposing major revisions will no doubt sound outlandish to many usability and human factors specialists. A number of objections can be raised to the modification of a successfu l metric, which is reliable and capable of driving the design of effective systems. This paper attempts to meet these objections, proposing an evolutionary perspective. Our belief is that the need for re-examination and update of the general usability framework is prompted by the powerful combination of technological progress, consumer expectations, and the evolution of novel applications. A new generation of interactive systems, utilizing varied animated characters, sophisticated behaviours, embodied conversational agents, and interfaces with 'personality' will revolutionize the way people interact with computers enlarging the bandwidth of communication to fully include social and affective dimensions (Picard, 1997; Cassell, 2000; Cassell, Sullivan, Prevost and Churchill, 2000). These next generation systems will elicit different psychological reactions from users; hence, they need to be evaluated in a specific framework respecting their key characteristics. Human-Computer Interaction (HCI) has many exa mples of successful frameworks and approaches that have been significantly modified as a result of the movement of the state of the art of ......

De Angeli, A., Johnson, G.I., & Coventry, L. (2001). The unfriendly user: exploring social reactions to chatterbots. In M.G. Helander, H.M. Kalid, T. Ming Po (Eds). Proceedings of the International Conference on Affective Human Factor Design, London: Asea

Pdf Abstract This paper presents a preliminary evaluation of Alice, a chatterbot designed in order to elicit anthropomorphic attributions and emotional reactions from those who chat to 'her'. The analysis is based on both transcripts of the interaction and user comments collected in a focus group. Results suggest that the introduction of explicit anthropomorphism in Human-Computer Interaction (HCI) is a complex phenomenon, which could generate strong negative reactions from the part of the user. The finding also demonstrates the importance of placing the development of user interfaces within a social framework as the technology tends to establish relationships with users. Keywords: Chatterbots, anthropomorphism, disembodied language, social dynamics.

De Angeli, A., Lynch, P. & Johnson, G.I. (2001). Personifying the e-market: A framework for social agents. In M. Hirose (Ed.). Human-Computer Interaction INTERACT'01, Amsterdam: IOS Press, 198-205.

Pdf Abstract This paper discusses our vision of the future with respect to the introduction of virtual assistants in the e-market. It presents the latest evolution of the involvement framework, an on-going model aimed at driving the design and the evaluation of social agents virtual characters designed to set up lasting relationships with the users. The framework is based on a review of the literature and on the systematic analysis of the first generation social agents available on the Web. Moreover, it is enriched by empirical results of two user-based evaluations of Granny, a social agent that tries to inject a specific personality into the interaction between a financial service provider and a customer. The assumption behind our research is that social agents require a reexamination of the traditional HCI approach to system design and evaluation. Both the usability framework and the media equation paradigm need to be updated to account for the peculiarity of the new interaction form. Keywords: social agents, user-experience, design and evaluation.

De Angeli, A., Gerbino, W., Nodari, E. and Petrelli, D. (1999). From tools to friends: Where is the borderline? Proceedings of the UM'99 Workshop on Attitude, Personality and Emotions in User-Adapted Interaction, Banff, Canada, June 23, 1-10.

Pdf Abstract A successful communication is mediated by at least three factors: (a) the initial mental model of the conversational partner; (b) the evolution of this model over the course of communication; (c) the speaker's individual ability to adapt to different partners. This simple framework can explain many different types of information exchange: from interpersonal conversation, to human-machine interaction. The entity that changes is the type of mental representation elicited by different targets. Tools elicit mental models (Johnson-Laird, 1983), representing the system in the form of available functionality and procedures to operate it. From these models, users inference about what the system is, how it works, and why it works that way (Carrol and Olson, 1988). On the contrary, persons elicit more complex representations integrating social and physical information. From these representations, speakers inference about behaviour, intentions, attitudes, emotions, ideas, and personality traits of other human being s. As a new generation of interfaces based on the assistant metaphor begins to evolve (see, for instance, the workshop on Behavior Planning for Life-Like Characters and Avatars), the representation induced by computers may drastically change. Normally, computers are perceived as cognitive artifacts: artificial tools that store, manipulate, and retrieve information (Norman, 1991). They are objects created by human beings to support representational functions and improve user's performances. Computers elaborate symbols. Because of this peculiarity, they have never been perceived exactly as machines, simple pieces of hardware. On the contrary, since the beginning of the computer age, a similarity with human beings has been detected and commonly proposed to explain the machine behaviour. As a consequence, computers have a memory and speak a language. During the last years, the human metaphor has been continuously strengthened. The evolution of interface techniques requires computers to be friendly with users ; intelligent agents should be artificial delegates. Agents are special entities: neither tools, nor friends. To be effective, they are expected to understand human needs, taking charge of routine operations, co-operatively driving the user towards the desired goal. Being "active", agents are different from traditional interfaces; being "artificial" they probably would never understand the whole complexity of human behaviour. Nevertheless, enhancing the interaction bandwidth between users and computers, agents have the potential for transforming computers into social artifacts. Agents are capable of setting up relationships with users and sometimes can respond socially to them. For all these reasons, Human-Computer Interaction (HCI) can now shift from a prevalent instrumental activity, involving mainly problem solving and reasoning capabilities, towards social cognition, a much more complex activity. Social cognition concerns how people make sense of other people and themselves, how humans create and mai ntain relationship with others, how people cooperate or compete with others. Cognitive activity occurs during interaction with tools, social cognition mediates our relationships with friends. Social stimuli are more complex than objects. Compared to objects, people are more likely to be causal agents, to perceive while they are perceived, to change because they are perceived, and to involve the observer self. Further, many important attributes of social stimuli are non directly observable (e.g., traits, intents, attitudes), and the accuracy of observations is hard to determine. All these difficulties may be enhanced in innovative HCI, because also very sophisticated agents will always be different from traditional social stimuli. Computers have a mixed status of social and non social objects (Turkle, 1995): the machine is animate, but not sentient. As a consequence, a number of fundamental social cues driving interpersonal interaction get lost during HCI. Moreover, current technology is not able to repro duce real conversations, the prototypical form of social exchange. When talking to a computer, humans maintain a conversational framework, but tend to reduce syntax complexity, utterance length, lexicon richness, and pronoun frequency (Johnsson and Dahlback, 1988). In other words, they select a simplified register, even if the (simulated) system displays human capabilities (De Angeli, 1991). This line of reasoning drive us towards the following conclusion. Agents are expected to be new objects of our social world. Therefore, even accepting that intelligent agents trigger social behaviour, we must be ready to differentiate agents from human beings. This imply understanding the innovative social codes and rules driving the interaction between users and agents. Such a knowledge is instrumental to a successful design. Effective technology requires a deep effort for understanding what or who agents are, and how agent characteristic influence users behaviour. At this aim, empirical research, especially in the form of early simulation, is instrumental to understand the innovative form of interaction. This aspect has been often disregarded. Nowadays, anthropomorphic agents are created without wondering what will be their impact on users behaviour or what makes them social. This paper is a preliminary contribution towards a predictive model explaining user behaviour during interaction with intelligent agents. Moving from the basic assumption that people plan their communicative behaviour having a representation of the partner in mind, it investigates the representation induced by systems based on different interaction paradigms. The first section reports some reflections on anthropomorphism in HCI and on the peculiar status of agents as social artifacts. Then, a simulation experiment is presented. Comparing the direct manipulation paradigm with an agent paradigm, it is aimed at providing an initial explanation about what factors are responsible for anthropomorphic attributions. To make the comparison meaningful, communication between users and agents was limited to typed natural language. Two dialogue styles were tested: a completely natural one and a restricted one. Results and implications of our findings for the design of effective agents are discussed in the final part.

De Angeli, A. (1995). Donne nelle reti elettroniche. Sistemi Intelligenti, 3, 373-391.

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Landragin, F., De Angeli, A., Wolff, F., Lopez, P. and Romary, L. (2002). Relevance and perceptual constraints in multimodal referring actions. In K. van Deemter and R. Kibble (Eds.), Information Sharing: Reference and Presupposition in Natural Language Generation and Interpretation, (pp. 391-410) Stanford CA: CSLI Publications.

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De Angeli, A. and Petrelli, D. (2000). Bridging the gap between NLP and HCI: A new synergy in the name of the user. CHI2000 Workshop on Natural Language Interfaces.

Pdf Abstract When usability became a major concern in system design, a dichotomy among visual and verbal language arose. Even if both interaction modalities were considered adequate to human capability, the past decades saw the dominance of the graphical approach. In this paradigm, the primary interaction style is Direct Manipulation (DM); verbal language is just a subordinated modality. Words or plain utterances (in the form of menus, error messages or icon labels) are used only when pictures and actions need to be disambiguated. This primitive form of Natural Language (NL) represents an asymmetric medium of communication, since verbal elements are meaningful only to the user. Till very recently, the Human-Computer Interaction (HCI) community has disregarded NL communication. A direct evidence for this claiming comes from a meta-analysis of previous CHI proceedings. In the period from 1995 to 1999, papers addressing written NL, speech or multimodal communication represent a very small minority, ranging from 3% in 19 95 and 1998 to 6% in 1996. At the same time, researchers who work in the NL Processing (NLP) field have been mainly interested in the computational treatment of linguistic inputs. With a few exceptions, designers neglected user studies, relying on the fact that the interaction would have been naturally user friendly.Despite this, a new tendency is emerging: HCI and NLP are recently unifying their effort to build innovative intelligent interfaces. The change elicits a number of questions that can be proposed as topics for discussion: (a) Are HCI and NLP complementary fields? (b); Where can they meet?; (c) How will NL modify HCI?

De Angeli, A. (1999). Linguaggio e gestualità nell'interazione con il computer: Verso il dialogo flessibile. Sistemi Intelligenti, 2, 333-357.

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De Angeli, A., Gerbino, W., Cassano, G. and Petrelli, D. (1998). Visual Display, pointing, and natural language: The power of multimodal interaction. In T. Catarci et al. (Eds.) Proceedings of the Working Conference on Advanced Visual Interfaces AVI'98, (pp. 164-173) ACM Press.

Pdf Abstract This paper examines user behavior during multimodal human-computer interaction (HCI). It discusses how pointing, natural language, and graphical layout should be integrated to enhance the usability of multimodal systems. Two experiments were run to study simulated systems capable of understanding written natural language and mouse-supported pointing gestures. Results allowed to: (a) develop a taxonomy of communication acts aimed at identifying targets; (b) determine the conditions under which specific referent identification strategies are likely to be produced; (c) suggest guidelines for designing effective multimodal interfaces; (d) show that performance is strongly influenced by interface graphical layout and by user expertise. Our study confirms the value of simulation as a tool for building HCI models and supports the basic idea that linguistic, visual, and motor cues can be integrated to favor effective multimodal communication.

De Angeli, A., Gerbino, W., Romary, L. and Wolff, F. (1999). The Ecological approach to multimodal system design. In A. Braffort et al. (Eds.), Gesture-based communication in Human-Computer Interaction, Lecture Notes in Artificial Intelligence 1739 (pp. 49-52), Berlin: Springer-Verlag.

Pdf Abstract Following the ecological approach to visual perception, this paper presents a framework that emphasizes the role of vision on referring actions. In particular, affordances are utilized to explain gestures variability in a multimodal human-computer interaction. Such a proposal is consistent with empirical findings obtained in different simulation studies showing how referring gestures are determined by the mutuality of information coming from the target and the set of movements available to the speaker. A prototype that follows anthropomorphic perceptual principles to analyze gestures has been developed and tested in preliminary computational validations.

De Angeli, A., Romary, L. and Wolff, F. (1999). Ecological interfaces: Extending the pointing paradigm by visual context. In P. Bouquet et al. (Eds.), Modeling and Using Context, Lecture Notes in Artificial Intelligence 1688 (pp. 91-104), Berlin: Springer-Verlag.

Pdf Abstract Following the ecological approach to visual perception, this paper presents an innovative framework for the design of multimodal systems. The proposal emphasises the role of the visual context on gestural communication. It is aimed at extending the concept of affordances to explain referring gesture variability. The validity of the approach is confirmed by results of a simulation experiment. A discussion of practical implications of our findings for software architecture design is presented.

De Angeli, A., Wolff, F., Lopez, P. and Romary, L. (1999). Relevance and perceptual constraints in multimodal referring actions. Proceedings of the Workshop on Deixis Demonstration and Deictic Belief, ESSLLI XI, 49-56.

Pdf Abstract This paper presents a first attempt to score the relevance of multimodal referring expressions within a task oriented environment. It is based upon the application of the ecological approach to multimodal system design, which in particular implies that perception has to play a central role in the understanding of a gestural designation. The results of an experimental work is presented, together with the scores obtained by combining the linguistic characteristic of the referring expression and the properties of the corresponding gestures (if any). Even if the calculus that we present has to be refined it seems to be already suited to validate our approach regarding the importance group salience and access type in the choice of a referring mode.

Wolff, F., De Angeli, A. and Romary, L. (1998). Acting on a visual word: The role of perception in multimodal HCI. Papers from the 1999 AAAI Workshop on Representations for Multimodal Human-Computer Interaction, Technical Report WS-98-09, AAAI Press, 89-93.

Pdf Abstract Following the ecological approach to visual perception, this paper investigates multimodal referring acts in Human- Computer Interaction. Preliminary results from a simulation experiment allow to: (a) clarify the effect of perceptual organization on multimodal communication; (b) provide guidelines for designing effective multimodal interfaces. Demonstrating that both the verbal and the gestural part of a referential act are influenced by perception, we confirm the need and the utility of taking into account perceptual organization to analyze referential expressions in a more robust way. As a conclusion, we show how these results can lead to an actual implementation of a gesture interpretation module directed by the reference analysis process.

Oviatt, S., De Angeli, A. and Kuhn, K. (1997). Integration and synchronization of input modes during multimodal human-computer interaction. CHI'97 Conference Proceedings, New York: ACM Press, 415-422; also in E. Andre (Ed.) Proceedings of the ACL Workshop on Referring Phenomena in a Multimedia Context and Their Computational Treatment, ACL/EACL-97, 1-13.

Pdf Abstract Our ability to develop robust multimodal systems will depend on knowledge of the natural integration patterns that typify people's combined use of different input modes. To provide a foundation for theory and design, the present research analyzed multimodal interaction while people spoke and wrote to a simulated dynamic map system. Task analysis revealed that multimodal interaction occurred most frequently during spatial location commands, and with intermediate frequency during selection commands. In addition, microanalysis of input signals identified sequential, simultaneous, point-and-speak, and compound integration patterns, as well as data on the temporal precedence of modes and on inter-modal lags. In synchronizing input streams, the temporal precedence of writing over speech was a major theme, with pen input conveying location information first in a sentence. Linguistic analysis also revealed that the spoken and written modes consistently supplied complementary semantic information, rather than re dundant. One long-term goal of this research is the development of predictive models of natural modality integration to guide the design of emerging multimodal architectures.

Petrelli, D., De Angeli, A., Gerbino, W. and Cassano, G. (1997). Referring in multimodal systems: The role of expertise and system features. In E. Andre (Ed.) Proceedings of the ACL Workshop on Referring Phenomena in a Multimedia Context and Their Computational Treatment, ACL/EACL-97, 14-20.

Pdf Abstract This paper empirically investigates how humans use reference in space when interacting with a multimodal system able to understand written natural language and pointing with the mouse. We verified that user expertise plays an important role in the use of multimodal systems: experienced users performed 84% multimodal inputs while inexpert only 30%. Moreover experienced are able to efficiently use multimodality shortening the written input and transferring part of the reference meaning on the pointing. Results showed also the importance of the system layout: when very short labels (one character) are available users strongly adopt a redundant reference strategy, i.e. they referred to the object in a linguistic way and use pointing too. Starting from these facts some guidelines for future multimodal systems are suggested.

De Angeli, A., Petrelli, D. and Gerbino, W. (1996). Interface features affecting deixis production: A simulation study. In L. Messing (Ed.) Proceedings of the ICSLP Workshop on the Integration of Gesture in Language and Speech, October 7-8, Newark and Wilmington Delaware, USA, pp. 195-204.

Pdf Abstract This paper examines gestural deixis production in a multimodal (natural language and pointing) interaction. Users (N=30) were required to fill in 4 forms by interacting with a simulated system. Labelling of Entry Fields (LEF, Complete-Partial; between-subject) and Feedback (Present-Absent within-subject) were manipulated in a 2*2 design. Results indicate that deixis occurred more frequently in the Partial-LEF condition. Specific input device constraints influenced intermodal integration: pointing was performed after the end of writing, although feedback presence increased modality shifts. Simulation offered a valuable tool for the development of multimodal interaction models. Keywords: nonverbal communication, body language, Sign language vs. gestures, deixis (deictic), language production

De Angeli, A., Coventry , L., Johnson, G., Renaud, K. (2005). Is a picture really worth a thousand words? Exploring the feasibility of graphical authentication systems. International Journal of Human-Computer Studies, 63 (1-2), 128-152.

Pdf Abstract The weakness of knowledge-based authentication systems, such as passwords and Personal Identification Numbers (PINs), is well known, and reflects an uneasy compromise between security and human memory constraints. Research has been undertaken for some years now into the feasibility of graphical authentication mechanisms in the hope that these will provide a more secure and memorable alternative. The graphical approach substitutes the exact recall of alphanumeric codes with the recognition of previously learnt pictures, a skill at which humans are remarkably proficient. So far, little attention has been devoted to usability and initial research has failed to conclusively establish significant memory improvement. This paper reports two user studies comparing several implementations of the graphical approach with PINs. Results demonstrate that pictures can be a solution to some problems relating to traditional knowledge-based authentication but that they are not a simple panacea, since a poor design can eliminate the picture superiority effect in memory. The paper concludes by discussing the potential of the graphical approach and providing guidelines for developers contemplating using these mechanisms. Keywords: User authentication; visual memory; usability; security

Renaud, K. and De Angeli, A. (2004). My password is here! An investigation into Visuo-Spatial Authentication Mechanisms. Interacting with Computers, 1-25.

Pdf Abstract Passwords are the almost universal authentication mechanism, even though they are basically flawed and cause problems for users due to poor memorability. Graphical methods of authentication have recently excited some interest but little is known about their actual efficacy. There are basically two types of graphical authentication mechanisms: recognition-based and location-based-also called visuo-spatial mechanisms. Whereas some kinds of recognition-based graphical authentication mechanisms have been evaluated by various researchers, there is still a need to investigate locationbased graphical authentication mechanisms in a more rigorous fashion to determine whether they could be a viable alternative to traditional passwords for web usage. This paper discusses graphical authentication mechanisms in general and reports on the evaluation of one particular visuo-spatial mechanism, aimed at augmenting the password paradigm by providing a way to record passwords securely. Results and findings are presented, and conclusions drawn, some of which can also be applied to other types of visuo-spatial mechanisms. We also propose a set of metrics which can be used to measure the quality of web authentication mechanisms and apply these to a range of existing authentication mechanisms. Keywords: User authentication; Graphical mechanisms; Visuo-spatial memory; Evaluation; Web authentication; Metrics

Coventry, L., De Angeli, A. and Johnson, G.I. (2003). Usability and biometric verification at the ATM interface. CHI 2003 Conference Proceedings, April 5-10, 2003, Fort Lauderdale, Florida, New York: ACM press, 153-160.

Pdf Abstract This paper describes some of the consumer-driven usability research conducted by NCR Self Service Strategic Solutions in the development of an understanding of usability and user acceptance of leadingedge biometrics verification techniques. We discuss biometric techniques in general and focus upon the usability phases and issues, associated with iris verification technology at the Automated Teller Machine (ATM) user interface. The paper concludes with a review of some of the major research issues encountered, and an outline of future work in the area. Keywords: ATMs, biometrics technology, iris verification, usability techniques.

Coventry, L., De Angeli, A. and Johnson, G.I. (2003). Biometric verification at a self-service interface. In P.T. McCabe (Ed.) Contemporary Ergonomics 2003 (pp. 247-252) London: Taylor & Francis.

Pdf Abstract The term biometrics refers to a variety of identification techniques, based on a physical, or behavioural user characteristic. Traditionally, access to ATMs, has been controlled by possession of an artefact (card) and knowledge of a Personal Identification Number (PIN). Biometric verification is a potential alternative. At NCR, investigations into biometrics have been undertaken over a number of years. These investigations have used a variety of methods to gradually acquire a sound understanding of consumers' issues. Our research has revealed a number of non-trivial issues with the introduction of this type of technology to the general public. We will present some of our findings and general understanding of the public's attitudes towards and behaviour with, biometrics verification in general and specifically fingerprint at the ATM.

De Angeli, A., Coventry, L, Johnson, G.I and Coutts, M. (2003). Usability and user authentication: Pictorial passwords vs. PIN. In P.T.McCabe, (Ed.). Contemporary Ergonomics 2003 (pp. 253-258) London: Taylor & Francis.

Pdf Abstract This paper presents the design and evaluation of the Visual Identification Protocol (VIP) an innovative solution to user authentication based on pictures and visual memory. Three authentication systems were prototyped and compared with the PIN approach in a longitudinal evaluation. The study revealed important knowledge about attitudes towards and behaviour with different authentication approaches. VIP was found to be easier to remember and preferred by users, but its usability can be easily disrupted by an inappropriate solution. A detailed error analysis is presented to help understand the limits and constraints of visual memory. This knowledge is instrumental in designing innovative authentication system of this type.

Coventry, L., De Angeli, A. and Johnson, G.I. (2003). Honest it's me! Self service verification. CHI 2003 Workshop on Human-Computer Interaction and Security Systems, April 5-10, 2003, Fort Lauderdale, Florida.

Pdf Abstract At NCR we have been involved with tracking and evaluating different biometric technologies for a number of years. We have adopted a pluralistic approach evaluating from both a technology and user perspective. Multiple evaluation techniques have also been used. Some of our findings and implementation implications have been summarised in this paper, from the consumers' perspective. We cover the issues of selecting a biometric, enrolment, consumer fears and ultimately consumer acceptance. Keywords: Biometric, verification, usability

Liddell, J., Renaud, K. and De Angeli, A. (2003). Using a combination of sound and images to authenticate web users. Short Paper HCI 2003. 17th Annual Human Computer Interaction Conference. Designing for Society. Bath, England. 8-12 Sept, 2003.

Pdf Abstract Passwords and pin numbers are ubiquitous even though they are basically flawed and cause problems for users due to memorability problems. There is a need for other mechanisms to be investigated. This paper explores a mechanism for web-based authentication which does not require any expensive hardware or extra software. Two experiments were conducted using a combination of sound and images to authenticate web site users ? exploiting users? associative memory strengths. The results and findings are presented, and conclusions drawn. Keywords: Authentication, Associative Memory, Memorability, Sound and Image.

De Angeli, A., Coutts, M., Coventry, L., Johnson, G.I, Cameron, D. and Fischer M. (2002). VIP: a visual approach to user authentication. Proceedings of the Working Conference on Advanced Visual Interfaces AVI 2002, ACM Press, pp. 316-323.

Pdf Abstract This paper addresses knowledge-based authentication systems in self-service technology presenting the design, implementation and evaluation of the Visual Pin concept. The basic idea behind it is to use pictures instead of numbers as a means for user authentication. Three different identification systems based on images and visual memory were designed and compared with the traditional PIN approach in a longitudinal study involving 61 users. The study addressed both performance criteria (number and types of errors, reaction time, action time) and subjective evaluation collected by a battery of psychometric instruments developed for this research. The study and associated design exploration revealed important knowledge about users and their attitudes towards and behaviour with authentication systems, including novel approaches using images. The Visual PIN was found to provide a promising and easy-to-use alternative to the numeric code. It is easier to remember, preferred by consumer and potentially more se cure. Results also provided guidelines to help designers make the best use of the natural power of visual memory in security solutions. A novel and successful procedure for enrolment is also discussed. Keywords: User authentication, security, visual memory, usability.

Culture & Design

De Angeli, A., Athavankar, U.A., Joshi, A., Coventry, L. and Johnson, G.I. (2004). Introducing ATM's in India: A contextual enquiry. Interacting with Computers special issue: Global human-computer systems, 16(1) 29-44.

Pdf Abstract This paper presents a method and results of an ethnographic study aimed at building an understanding of Automatic Teller Machine (ATM) adoption in Mumbai, India. The study combined field observations and semi-structured interviews (N=43) of early ATM adopters, bank customers who do not use ATMs, and people who used the ATM for the first time as part of our research. Data were analysed to identify specific cultural traits that may affect the adoption of ATMs in urban India. Results demonstrated the unique role of the cultural context in affecting users' expectations and behavioural possibilities, thus determining people's response to the machine. This led to the conclusion that an understanding of cultural biases and metaphors can facilitate technology diffusion and acceptance informing design localisation and supporting the development of strategies to motivate and train users. Keywords: ATMs adoption; Design localisation; Hofstede's culture dimensions; Emerging market; Ethnography, Cross-cultural user research.

De Angeli, A., Coventry, L., Johnson, G.I. (2003). ATM's adoption in developing countries: Deja' vu or not? 2nd BCS HCI Group Workshop on Culture and HCI: Bridging Cultural and Digital Divides.

Pdf Abstract This paper proposes some thoughts on, and insights into, technology adoption in different cultural contexts, analysing the relationship between Hoffstede's cultural value dimensions and ATM's adoption in urban India. It is based on an ethnographic study carried out in Mumbai in autumn 2002 combining field observations and structured interviews (N=43). The sample consisted of early ATM users, bank customers who have not chosen to use ATM's, and first time users, or people who decided to try out an ATM for the first time as part of our research. Findings are analysed to identify specific cultural issues which are likely to affect the adoption of ATM's in urban India and compare this process with existing knowledge of ATM adoption in western countries.

E-learning

Costabile, M.F., De Angeli, A., Roselli, T., Lanzilotti, R. and Plantamura, P. (2003). Evaluating the educational impact of a tutoring hypermedia for children. Information Technology in Childhood Education Annual, 1, 289-308.

Pdf Abstract Several hypermedia environments have been developed in the last few years with the intention of promoting the acquisition of knowledge on a wide range of topics and developing problem-solving abilities. However, there are many different and sometimes conflicting claims about the capability of these environments to promote meaningful learning. We have developed a hypermedia learning environment with a tutorial component that exploits Artificial Intelligence techniques. This hypermedia, called Logiocando, targets a special category of users, namely children of the fourth level of primary school (9-10 years old), to teach them basic concepts of logic. Two empirical evaluations of the educational impact of Logiocando have been performed. Such experiments compared two teaching approaches: the computer-based one that relies on the hypermedia system, and the traditional one that relies on classroom instruction. The studies involved a total of 94 pupils from a primary school. Results showed that Logiocando can c ertainly be considered a valid support in the process of learning and deepening logic knowledge, provided that children are adequately motivated. Keywords: Intelligent tutoring hypermedia, pedagogical efficiency, usability, user-centred design.

Costabile, M.F., Roselli, T., Lanzilotti, R., Plantamura, P. and De Angeli, A. (2003). Does Hypermedia really work for tutoring children? IEEE Multimedia, April-June, 65-69.

Pdf Abstract The advent of multimedia technology has produced an explosion of research on the use of computers in education. Indeed, the computer is a rich communication tool that instructors can use for effectively illustrating ideas. However, compared to human communication, computers lack several features needed for satisfactory communication. They don't have analogies to eyes, ears, voice, and hands that humans use for acquiring information; neither can they create different information representations. Graphic, video, animation, and sound use in multimedia systems attempts to overcome these limitations to develop systems that can better communicate and cooperate with humans. Several recently developed hypermedia environments - both online (on the World Wide Web) or offline (on CD-ROM) - promote knowledge acquisition on a wide range of topics and attempt to teach problem-solving abilities in users. However, the basic question of whether hypermedia learning environments actually promote learning is still debatable , Our work here refers to a hypermedia designed for a particular category of users, namely children in a primary school. The hypermedia offers a tutoring component to teach basic logic concepts to children. We call this hypermedia Logiocando, a name obtained by merging two Italian words (Logica Giocando) and meaning "playing with logic." To determine whether this tutoring hypermedia really works (that is, to check its instructional validity), we performed two experiments that evaluated the pedagogical efficiency of the hypermedia in comparison to traditional classroom instruction.

Costabile, M.F., De Angeli, A., Roselli, T. (2001). Experimental evaluation of an intelligent tutoring system. In N. Avouris and N. Fakotakis, Advances in Human-Computer Interaction I (pp. 135-139) Patras: Typorama.

Pdf Abstract Several hypermedia learning environments have been de-veloped in the last years, with the objective of helping students to acquire specific concepts on a given topic, as well as problem-solving abilities. However, there are still many different and sometimes conflicting claims about learning effectiveness by means of such environments. We present an empirical evaluation of a learning hyper-media with a tutorial component that exploits Artificial Intelligence techniques. This hypermedia, called Logio-cando, has been designed to be used by a special cate-gory of users, namely children of the fourth level of pri-mary school, to help them to learn basic concepts of logic. This category of users demands special attention to usability of the hypermedia. For this reason, project and development of the hypermedia have been carried out fol-lowing a strict user-centred methodology, in order to build a system that satisfies clear usability objectives. The aim of the controlled experiment here reported was to evalua te the learning effectiveness of Logiocando and to estimate the difference between two approaches: the computer-based one, that uses a hypermedia system, and the traditional one, that uses the typical lesson in class-room. The results have shown that the hypermedia can certainly be considered a valid support in the process of learning and deepening a topic. Keywords: Intelligent tutoring hypermedia, usability, user-centred design, learning effectiveness.

Usability & 'New' Usability

Sutcliffe, A. and De Angeli, A. (2005). Assessing Interaction Styles in Web User Interfaces. Interact 2005. LNCS 3585, 406-417.

Pdf Abstract An evaluation of two websites with the same content but different interface styles (traditional menu-based and interactive metaphors) is described. A formative usability evaluation was carried out with heuristic assessment of aesthetics followed by post-test memory. The subjects had more problems with the metaphor-based site, but rated it more favourably on the aesthetics heuristics. There was no difference in free memory recall between the sites. The implications for website design and evaluation are discussed.

De Angeli, A., Matera, M., Costabile, M.F., Garzotto, F. and Paolini, P. (2003). On the advantages of a systematic inspection for evaluating hypermedia usability. International Journal of Human-Computer Interaction. 15(3).

Pdf Abstract It is indubitable that usability inspection of complex hypermedia is still an "art", in the sense that a great deal is left to the skills, experience, and ability of the inspectors. Training inspectors is difficult and often quite expensive. The SUE inspection technique has been proposed to help usability inspectors share and transfer their evaluation know-how, to simplify the hypermedia inspection process for newcomers, and to achieve more effective and efficient evaluation results. SUE inspection is based on the use of evaluation patterns, called Abstract Tasks, which precisely describe the activities to be performed by evaluators during inspection. This paper highlights the advantages of this inspection technique, by presenting its empirical validation through a controlled experiment. Two groups of novice inspectors have been asked to evaluate a commercial hypermedia CD-ROM applying the SUE inspection or the traditional heuristic evaluation. The comparison was based on three major dimensions: effectiv eness, efficiency, and satisfaction. Results have shown a clear advantage of the SUE inspection over the traditional inspection on all dimensions, demonstrating that Abstract Tasks are efficient tools to drive the evaluator's performance.

Costabile, M.F., De Angeli, A. and Matera, M. (2001). Guiding usability evaluators during hypermedia inspection. Proceedings of IEEE Symposia on Human-Centric Computing Languages and Environments. Stresa, Italy, 5-7 September, 332-333.

Pdf Abstract This paper presents an empirical validation of the Abstract Tasks (ATs), which are operational guidelines driving the inspection activities during a usability evaluation. Two groups of inspectors evaluated a multimedia CD-ROM, one group using the ATs, the other group using a list of heuristics. Results demonstrated a better performance of the AT group but raised some issues concerning the acceptability of the technique.

De Angeli, A., Matera, M., Costabile, M.F., Garzotto, F. and Paolini, P. (2000). Validating the SUE inspection technique. In Di Gesu’ et al. (Eds.) Proceedings of the Working Conference on Advanced Visual Interfaces AVI 2000, ACM Press, 142-150.

Pdf Abstract In the usability inspection of complex hypermedia a great deal is left to the skills, experience, and ability of the inspectors. The SUE inspection technique has been proposed to help usability inspectors share and transfer their evaluation know-how, make it easier the hypermedia inspection process for newcomers, and achieve more effective and efficient evaluations. The SUE inspection is based on the use of evaluation patterns, called Abstract Tasks, which precisely describe the activities to be performed by evaluators during inspection. This paper presents an empirical validation of this inspection technique: two groups of novice inspectors have been asked to evaluate a commercial hypermedia CD-ROM applying the SUE inspection or the traditional heuristic evaluation technique. Results have shown a clear advantage of the SUE inspection over the heuristic evaluation, demonstrating that Abstract Tasks are efficient tools to drive evaluator's performance.

Driving behaviour

Toffetti, A. Nodari, E., Zoldan, C., De Angeli, A., Gerbino, W. (2001). Analisi ergonomica con esperti di INFO2000. Atti del simposio su Human-Computer Interaction HCITALY 2001, VII Congresso della Societa' Italiana di Ergonomia (SIE), Firenze, September 26-27.

Pdf Abstract In questo articolo viene descritto un metodo di analisi euristica, derivato dalle metodologie utilizzate nel campo della 'Usability Engineering' e adattato al contesto automotive. Questo metodo viene applicato per progettare e valutare i dispositivi di bordo, in particolare quelli pi ricchi di funzionalita'. Viene qui riportata l'analisi euristica eseguita su un prototipo di sistema informativo denominato INFO2000. La fase di analisi del sistema con esperti stata seguita da una fase di progettazione di alcune funzioni non ancora implementate. La valutazione stata effettuata in due parti: alla prima fase di valutazione condotta dagli esperti, seguita una fase di valutazione con utenti. Lo scopo dell'analisi con esperti stato duplice: da una parte evidenziare e superare eventuali problemi di usabilita' dell'interfaccia ed ottimizzarla in relazione al contesto di guida in cui dovrebbe essere utilizzata (Intervento di analisi); dall'altra parte, progettare le nuove funzioni del sistema ancora in fase di sviluppo (Intervento di progettazione).

Toffetti, A., Nodari, E., Zoldan, C., De Angeli, A., and Gerbino, W. (2000). Age-related differences in driver-INFO2000 interaction. Proceedings of the 6th ERCIM Workshop on User Interfaces for All. Firenze, Italy, October 25-26, 362-363.

Pdf Abstract These pages summarize the user-based evaluation of INFO2000, the prototype of a multifunctional in-car information system. The aim of the study was to investigate the very first impact of INFO2000 on both young and elderly potential users. It emerged that INFO2000 was initially less usable for elderly. Nevertheless, this difference tended to diminish with the practice and the elderly attitude towards the system was positive.

De Angeli, A. et al. (1996). Driver reaction and behavior in a motorway environment equipped with an integrated VMS and on-board RDS-TMC information system. Proceedings of the Third Annual World Congress on Intelligent Transport Systems, Orlando, Florida, October, pp. 14-18.

Pdf

Gerbino, W., Ferrante, D., De Angeli, A. and Plet, S. (1995). Evaluation methods for driver support systems. Comunicazioni delConvegno Internazionale di Ergonomia Cognitiva, Padova, Italy, pp. 53-54.

Others

Ardito, C., Costabile, M.F., De Angeli, A., Pittarello, F. (to appear). Navigation help in 3D Worlds: some empirical evidences on use of sound. Multimedia Tools and Applications.

Pdf Abstract The concept of Interaction Locus (IL) has been introduced to help the users to orient, navigate, and identify relevant interaction areas in 3D Virtual Environments (VEs). The IL is a multimodal concept: it adds to the 3D visual scene parallel information channels that are perceived by other senses. In particular, the IL emphasizes the role of music as a navigation aid in a VE. This paper reports three user-evaluations of different IL enriched virtual worlds, and in particular of the role of the IL auditory component. Results suggest that audio in 3D plays not only an aesthetic role, which the users greatly appreciate, but also a functional role simplifying navigation and helping the users to recognise scenes in the environment. Such a functional role however is subordinated to a proper understanding of the link between music and virtual space. While these experiments refer to desktop virtual reality environments, their findings are general enough to inform the design of navigational tools for other segments of the mixed reality domain. Keywords: Auditory Interfaces, Experimental Evaluations, Interaction Locus, Usability, Virtual Environments

Costabile, M.F., De Angeli, A., Pittarello, F. and Ardito, C. (2003). Can audio help navigating in virtual environments? An experimental evaluation. Human-Computer Interaction INTERACT'03, Zurich, September 2003.

Pdf Abstract The concept of Interaction Locus (IL) has been introduced to help the users to orient, navigate, and identify relevant interaction areas in 3D Virtual Environments (VE). The IL is a multimodal concept: it adds to the 3D visual scene parallel information channels that are perceived by other senses. In particular, the IL emphasizes the role of music as a navigation aid in a VE. The paper reports two experimental evaluations of the audio component of the IL, as implemented in the web site of a famous Italian Museum. The experiments investigated the different roles (functional or aesthetic) that a music component may play in VE navigation and content fruition. Results suggest that music plays an aesthetic role that the users appreciate very much. It can also plays a functional role, helping users to recognise scenes in a VE, provided that the users are informed in advance of the semantic linkage between music and virtual space. Keywords: Virtual Environment, Usability, Audio Help, Web Museum, Experimental Evaluations

Coventry, L., Johnson, G. and De Angeli, A. (2002). Achieving accessibility through personalisation. Proceedings of HCI 2002, Banff London, short papers.

Pdf Abstract Accessibility is a goal towards which all public technology should aim. That is, to create technology which is usable by all people, regardless of their abilities. Achievement of this goal is limited by what is possible with current technology, what is commercially viable, and what is understood about matching technology to individuals, particularly of people with disabilities which can create barriers to Automated Teller Machine (ATM) access. This paper presents findings of our initial studies on the accessibility of ATMs.

De Angeli, A. and Gerbino, W. (1999). La psicologia della HCI. In M.F. Costabile and F. Paternò (Eds.) Atti di HCItaly'99, Roma, February 9.

Pdf Abstract Questo lavoro presenta alcune riflessioni sul contributo della psicologia alla progettazione di sistemi informatici. Attraverso la ricostruzione storica del ruolo delle scienze umane nella HCI, si vuole dimostrare la necessit dello sviluppo di una specifica psicologia della HCI, una disciplina di confine in cui confluisca parte dell'apparato teorico e metodologico della psicologia cognitiva, sociale e applicata. L'attuale stadio tecnologico che si concentra sullo sviluppo di sistemi intelligenti e flessibili presuppone infatti conoscenze psicologiche evolute che richiedono di superare le tradizionali barriere fra le varie aree di studio del comportamento umano.

Petrelli, D., De Angeli, A. and Convertino, G. (1999). A user-centered approach to user modelling. In J. Kay (Ed.) UM99 User Modeling, CISM Courses and lectures N. 407 (pp. 255-264) New York: Springer-Verlag, (award nominee paper).

Pdf Abstract Generally, user modeling concerns a person interacting with a standing console. This scenario does not represent the HyperAudio system in use: a visitor freely moves in a museum, gathering information from an adaptive and portable electronic guide. To provide designers with presumptive user behavior, data about visitor profiles and visit styles were collected through a questionnaire. The study pointed out unpredicted situations (e.g., the importance of social context) and confirmed some working hypotheses (e.g., the relevance of visit span). This paper reports on this experience, describing how to go from designer questions to guidelines for user modeling, making the best use of empirical data.

Bruno, N., De Angeli, A. and Gerbino, W. (1994). Visual cognitive factors in the evaluation of graphical user interfaces. In A. Grieco et al. (Eds.), Book of Short Papers WWDU'94, vol. II, Milano, October 2-5, 16-17.

Pdf

De Angeli, A. (1997).Valutare i sistemi flessibili un approccio globale alla HCI (Evaluating flexible systems: A global approach to HCI). PhD thesis, Psychology Dept. University of Trieste.

Pdf (Italian_only)

De Angeli, A. (1991). Dillo a maia: Un esperimento di interazione uomo-macchina (Talking to Maia: a Human-Machine Interaction Experiment). Master's thesis, Psychology Dept. University of Trieste.

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