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Understanding how interfaces

affect users

5.1 Introduction
5.2 What are affective aspects?
5.3 Expressive interfaces
5.4 User frustration
5.5 A debate: the application of anthropomorphism to interaction design
5.6 Virtual characters: agents
5.6.1 Kinds of agents
5.6.2 General design concerns: believability of virtual characters

5.1 Introduction
An overarching goal of interaction design is to develop interactive systems that
elicit positive responses from users, such as feeling at ease, being comfortable, and
enjoying the experience of using them. More recently, designers have become in-
terested in how to design interactive products that elicit specific kinds of emotional
responses in users, motivating them to learn, play, be creative, and be social. There
is also a growing concern with how to design websites that people can trust, that
make them feel comfortable about divulging personal information or making a
purchase.
We refer to this newly emerging area of interaction design as affective aspects.
In this chapter we look at how and why the design of computer systems cause cer-
tain kinds of emotional responses in users. We begin by looking in general at ex-
pressive interfaces, examining the role of an interface's appearance on users and
how it affects usability. We then examine how computer systems elicit negative re-
sponses, e.g., user frustration. Following this, we present a debate on the controver-
sial topic of anthropomorphism and its implications for designing applications to
have human-like qualities. Finally, we examine the range of virtual characters de-
signed to motivate people to learn, buy, listen, etc., and consider how useful and
appropriate they are.