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498 CHAPTER 16 Working with research participants with disabilities

in 3.5 hours. This same amount of time might be frustrating to someone who has
utilized the equipment for years. Each user with a disability (or a combination of
disabilities) is a unique individual, with a unique performance speed that they alone
consider to be their average “default speed.” The “default speed” should be taken
into consideration to determine individual usability. However, the “default speed”
can also be a complication when trying to compare the performance of a group of
users with a specific disability. For instance, typical data input and output speeds
vary more greatly for users with disabilities than for the general user population.
As an example, Blind users listen to their screen readers (e.g., JAWS, VoiceOver, and
Window-Eyes) at varying rates, and tend to think that any speed that is not their pre-
set speed is either too fast or too slow. In experimental studies with Blind users, you
may want to remove the potential confounding factor of having various screen reader
speeds in the mix by using one screen reader speed for every participant, although
this may frustrate the individuals who participate. Alternatively, you might check the
speech rate that each user has set on their computer, but note that they will not be
comparable across different screen reader brands.
In another example of the complexity of user differences within a specific impair-
ment population, for a screen reader user who listens to the screen reader at a very
rapid rate, they may be frustrated if a task takes more than 5 minutes to complete.
Another user, who listens to the screen reader at a much slower speed, may be very
satisfied if the same task takes 20 minutes to complete. Their personal expectations
of performance may not always be obvious to the researcher and this may be hard
to measure. Experience with the computer and confidence may also play a role. For
instance, imagine three Blind users, all of whom are attempting the same task. User
A may give up after 2 minutes of attempting the task, because they know that they
typically can only find information using four different navigation methods, and once
they have attempted all four navigation methods, it is pointless to continue, as they
are confident that they would not be able to use any other method and succeed. User B
may also give up after 2 minutes, but because they have low confidence. They are not
confident in their abilities and think it is unlikely that they will be able to complete
a task. User C does not give up, even after 45 minutes of attempting a task. While
the computing skill set of user C might be high or low, they are confident in their
abilities, and they repeatedly say, “I am not a quitter. I will keep going until I am able
to complete the task.” The authors of this book have personally witnessed all three
behaviors. In this example, time is not directly correlated to technical experience
or confidence, but rather, is influenced by both.
Experience can also play a factor in how people with disabilities perceive the user
experience. For instance, Blind users often do not subjectively rate interface prob-
lems as being as bad as the objective performance ratings document (Trewin et al.,
2015). One possible reason for this is that their previous experience with technology
includes so many barriers to be overcome, that their expectations for their interaction
experience are a low baseline, and interface problems may not be perceived as bad
as they really are (Trewin et al., 2015). For instance, the research documents that
Blind users may generally have a positive outlook (Trewin et al., 2015), and interface