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investigations often focus upon representative users and use cases, omitting
extreme cases. As understandable as this strategy might be, a focus on
general cases may miss out on some of the insights that might be gained from
examining less familiar perspectives.
Geo-location services—tools that combine global positioning system
(GPS) facilities with data and communication tools—have spawned numerous
computing tools and services. Possibilities include facilities for finding nearby
friends or restaurants; games; educational systems based on the location of
items of interest in natural environments; and location-based data collection
covering entire cities.
A case study based on extremes was used to explore some of the questions
regarding perceptions of location and privacy (Troshynski et al., 2008). This
investigation examined the habits and perceptions of a group of sex offenders
who were required to have their locations tracked via GPS as part of their
parole agreements. Building from theories that argue that marginalized groups
may possess instructive insights into society, these researchers hoped to use
this extreme population to reconsider HCI questions about location-based
systems. Data collection involved semistructured focus group sessions with 10
parolees who were already participating in a pilot study on the use of GPS for
parole supervision for sex offenders. Although several individuals participated,
comments were analyzed as an undifferentiated whole, making this a single-
case study of the group of parolees.
Analysis of the focus group data led to the identification of three main
themes describing the impact of the system on the participants. The GPS
systems structured their perception of space, making them acutely aware of
how far they were from home and how close they may have come to forbidden
locations such as schools and parks. The systems also constrained their time:
the need to regularly charge batteries limited their ability to spend long periods
of time away from convenient sources of electricity. The parolees' sense of their
bodies was also changed, as the ankle-mounted GPS units both made certain
clothing choices (such as short pants) impractical and effectively prohibited
swimming, bathing, or other activities that might have exposed the unit to the
possibility of water damage. The researchers used these insights to fuel a more
general consideration of location-based interfaces in specific social and cultural
contexts (Troshynski et al., 2008).
The value of these extreme cases lies in the distance between their
perspectives and motivations and those of “typical” users of GPS-based
computing systems. Generalization was not the goal of this study—it is hard
to see how the concerns of a group of parolees who were required to use these
systems might be applied to voluntary users of location-based systems for
game playing or locating friends. Instead, the comments of this atypical user
group provided a richer understanding that might not have emerged through
investigation of the expected case.