Conclusions - Modeling Users' Experiences with Interactive Systems - page 136

7.1.1 Conceptualizing Diversity in User Experience

A long-standing assumption in the field of psychophysics is that different individ-
uals will more or less agree on perceptual judgments such as how much noise, or
blur, an image contains, or how much friction, or inertia, one may find in a haptic
control. This work highlighted that this assumption, often referred to as the princi-
ple of homogeneity of perception (Martens, 2003), does not necessarily hold in the
context of cognitive judgments of the quality of interactive products.
Using a framework from (Hassenzahl, 2005), we conceptualized diversity as ex-
isting at two different stages in the formation of an overall evaluative judgment about
an interactive product. Perceptual diversity lies in the process of forming product
quality perceptions (e.g. novel, easy to use) on the basis of product features. For in-
stance, different individuals may infer different levels on a given quality of the same
product, e.g. disagree on its novelty. Evaluative diversity lies in the process of form-
ing overall evaluations of the product (e.g. good-bad) on the basis of product quality
perceptions. For instance, different individuals may form different evaluative judg-
ments even while having no disagreement on the perceived quality of the product,
e.g. both might think of it as a novel and hard-to-use product, but they disagree on
the relative importance of each quality.

7.1.2 Establishing Empirical Evidence for the Prevalence of

Diversity in User Experience

We identified two critical sources for diversity in the context of users' experiences
with interactive products: (a) interpersonal diversity in users' responses to early
conceptual designs, and (b) dynamics of users' experiences over time.

7.1.2.1 Interpersonal Diversity in Users' Responses to Early Conceptual

Designs

Den Ouden (2006) highlighted that design decisions made early in the conceptual
phase and particularly the ones relating to product definition are responsible for the
majority of soft reliability problems. This leads to questioning the degree to which
such design decisions are grounded on empirical insights about users' preferences.
Based on a number of informal communications with stakeholders in concept de-
sign practices, we observed that it is often difficult to trace back the reasons that
motivated certain design decisions. The questions raised then were on what basis
are design decisions made? Can designers really foresee users' preferences? Chap-
ter 2 presented a study that inquired into the differences between designers' and
users' views on a set of early conceptual designs. The study highlighted that de-
signers' views can be substantially different from the ones of designers. Even in
a case where designers and users preferred the same product, users were found to
base their preference on substantially different reasons, i.e. they valued different
product qualities than the ones valued by the designers. It was further highlighted
that both designers and users, in judging the quality of these conceptual designs,