Introduction - Modeling Users' Experiences with Interactive Systems - page 2

main uncertainty in new product development projects; while in the '90s the uncer-
tainty related to the technology in relation to cost-effective mass production, in the
current market the dominant uncertainty relates to the attractiveness of the product
and users' expectations about the product functions.
These trends are reflected in the development of the field of Human-Computer
Interaction, from the study of usability as a critical factor to the acceptance of inter-
active products, to a more holistic understanding of users' experiences with inter-
active products, leading to the study of new concepts like pleasure (Jordan, 2000),
fun (Blythe et al., 2003), aesthetics (Tractinsky et al., 2000) and hedonic qualities
(Hassenzahl, 2004). While a wealth of techniques and methods exist for ensuring
the usability of interactive products, research on user experience evaluation meth-
ods is only at its infancy. This topic aims at highlighting methodological issues in
user experience evaluation and proposes a number of methods for inquiring into
users' experiences with interactive products.

1.1 From Usability to Experience

The field of Human-Computer Interaction was for a long time identified as the field
of usability engineering. Usability was seen as critical to user acceptance and a
wealth of principles (e.g., Norman, 1988), design guidelines (e.g., Nielsen and
Bellcore, 1992) and evaluation techniques (e.g., Dix et al., 2004) have become in-
strumental in the development of usable products. The field of usability engineering
readily acknowledged the dual nature of the usability concept: its objective and sub-
jective side. One of the most dominant definitions of usability, for instance, the ISO
9241-11 standard (1996) defines usability as

“the extend to which a product can be used by specific users to achieve speci-
fied goals with effectiveness, efficiency and satisfaction in a specified context
of use”.

Effectiveness represents the accuracy and completeness with which users achieve
certain goals and is typically measured through observed error rates, binary task
completion, and quality of the outcome for a given task (see Frøkjær et al., 2000;
Hornbæk and Law, 2007). Efficiency can be characterized as effectiveness in rela-
tion to resources spent and is typically measured through task completion time and
learning time. One can note that both these components, effectiveness and efficiency
represent the objective side of usability. The third component, user satisfaction, rep-
resents users' comfort in using and overall attitude to the product and is typically
measured through psychometric scales on overall preference, product quality per-
ceptions and specific attitudes towards the interface (see Hornbæk and Law, 2007).
An assumption underlying the distinction between the subjective and objective
side of usability was that these two would strongly correlate. Nielsen and Levy
(1994), in a meta-analysis of a selected set of 57 studies found that in 75% of the
cases, users' overall preference was strongly related to overall performance. These
findings have, however, been repeatedly questioned in subsequent studies suggesting