Large Scale User Trials - Human-Computer Interaction and Innovation in Handheld, Mobile and Wearable Technologies - page 146

people now regularly carrying mobile computing
devices with them. Allied to this has been the
creation of a number of 'app stores' on various
platforms for distributing applications to these
mobile devices. Such distribution mechanisms
offer great potential to researchers in recruiting far
larger numbers of users than is currently typical
for ubicomp trials. To study this method of recruit-
ment and assess its implications for conducting
research, we ported Feeding Yoshi to the iPhone,
calling it Hungry Yoshi (McMillan et al, 2010). By
releasing the app as a free download via a public
software repository we aimed to attract large
numbers of users from all over the world. Users
could install the app through a mechanism that
they were already comfortable with and we hoped
that having the application on their own devices
would lead to more naturalistic interactions.
In pioneering this form of distribution for
large-scale ubicomp system trials, we were able
to further explore the boundaries of time and space
in ubicomp applications and examine the use of
existing evaluation techniques. The Hungry Yoshi
trial began in September 2009 and is still ongoing
(At the time of writing the trial has been running
for a year.) The trial has included qualitative and
quantitative data analysis and engaging users
worldwide in the iterative design and adaptation
of the game.
Like Ego and the earlier version of Feeding
Yoshi, interacting with participants was the great-
est challenge in Hungry Yoshi. Our first dialogue
with users was to explain the nature of the trial and
gain consent that any data generated from the user
could be used for the purposes of our research.
As such, a terms and conditions screen is shown
on first launch, explaining the trial, who the re-
searchers are, the information we record through
use of the application, ways of contacting us and
ways to opt out of the trial. Since the application
is submitted to a global audience, these terms are
provided in four different languages. These terms
had to be agreed to before the user could begin to
use the application.

Although users were informed of the nature of
the trial on first launch, the majority did not physi-
cally meet with researchers and as such evaluator
contact with participants had to be approached
in a different manner. The users had not come
to us explicitly as 'trial participants', but were
simply smartphone owners wishing to download
and play a new game that had become available
on the store. As this was a new scenario for us
as evaluators, we saw the need to introduce two
new mechanisms into the evaluation to remain in
contact with participants: tools for communication
within Hungry Yoshi, and communication via a
social networking web site.
Following on from the use of FlexFill to elicit
responses to evaluator-posed questions during a
trial, Hungry Yoshi included communication with
researchers built into the app as a game feature.
Within the game itself we built a mechanism
that enabled users to earn 'tokens' to help them
in the game by performing tasks that were set by
researchers throughout the course of the trial. In
this way, we could relay messages to participants,
ask specific questions and receive feedback as
appropriate.
In addition to the task system, FlexiFill was
extended to make use of Facebook, a popular
online social networking application. Facebook
was used as a means of facilitating more in-depth
dialogues and to support communication between
participants themselves. Users could optionally
log into the application using Facebook Connect,
a service with an iPhone API that allows users to
verify themselves and log in to third party sites
and applications using their Facebook accounts. In
establishing links via Facebook, it was also pos-
sible to contact participants to set up interviews via
telephone or Skype, so that more qualitative means
of evaluation could be performed. In running the
trial of Hungry Yoshi with a set of participants
we never physically met, we as researchers were
further detached from interviewees again, as had
been the case when moving from Treasure to the
original version of Feeding Yoshi. However, by