good example of this is the availability
of differing speech rates for text-to-speech on VoiceOver for the iPhone
(Figure 1). The fastest rate is not very
understandable to people not used to it,
but is often preferred by blind users.
Ability-based design. One way to
realize universal design is ability-based
design as defined by Wobbrock et al. [ 5].
Ability-based design encourages
designers to focus on users’ abilities to
build into the system efficient ways to
make the system adapt to their abilities.
The system could adapt automatically,
or, more commonly, the system has user-selectable options to make the system
work effectively for a user’s abilities.
The speaking-rate slider for VoiceOver
is a great example. An ability-based
designer would know that reading text
through speech is intrinsically slower
than visually reading text. She would
know that speech can be sped up and,
with practice, still be understood. A
typical designer would likely assume the
most usable design for a text-to-speech
application is to make the speech as
natural as possible and not think about
less-natural rapid speech. By contrast,
the ability-based designer’s approach
yields a design that meets the needs of
users who are blind and have abilities
the average person does not.
Since it is often the case that designers
of technology are not necessarily the
users of that technology, it is important
they engage users in order to achieve
usable designs. This is especially
true for users with disabilities whose
abilities are not well understood by the
designers. User engagement is codified
in the ISO standard ISO 9241-210:2010
Ergonomics of human-system interaction
— Part 210: Human-centered design for
interactive systems, which delineates six
• The design is based upon an explicit
understanding of users, tasks, and
• Users are involved throughout
design and development.
• The design is driven and refined by
• The process is iterative.
• The design addresses the whole user
• The design team includes
multidisciplinary skills and
These principles are especially
DESIGN FOR USER
useful when thinking about designing
for people with disabilities using the
universal design approach. Since
typical designers and developers are
not disabled, how are they to practice
human-centered design? The design
cycle typically has four components:
analyzing, designing, prototyping,
and testing. The four-step process is
repeated until a satisfactory result
is obtained. At a minimum, in user-
centered design users are employed
in testing to determine the usability
by users with disabilities [ 6].
Unfortunately, it may be that that the
initial analysis and design is flawed, so
employing users earlier in the process
might be beneficial. In participatory
design (or co-design), users are also part
of the design team, helping to come up
with the requirements and features of
the design [ 7]. Finally, there is design
for user empowerment, where users
participate in all four steps of the
design cycle. User empowerment is a
concept I first introduced in a 2008
article [ 8] but have since refined.
Figure 2 describes these approaches.
The user-centered and participatory
design processes have the advantage
that the resulting designs from these
approaches are more likely to be
adopted by users with disabilities.
However, there is still something
paternalistic about having these
users participate only in the testing
and in designing the requirements
and features. In design for user
empowerment, users develop the
project, design the requirements and
features, develop the prototypes,
test the prototypes, and analyze the
results of testing to refine the design.
Naturally, it might not be the same
people involved in all these steps. For
example, designers and developers
should not be testers. The main reason
that people with disabilities should be
so deeply involved is that they have the
biggest stake in the eventual product.
In my view, there are two main
human characteristics needed for design
for empowerment: self-determination
and technical expertise. I will explore
each of these in more detail.
Self-determination. Self-determination means that those
with disabilities have control of, and
are not just passive recipients of,
Figure 2. Basic design cycle, user-centered
design, participatory design, and design for
INTERACTIONS.ACM.ORG MARCH–APRIL 2015 INTERACTIONS 27