Interactions - November/December 2014

that failure to complete the associated task would have dire consequences. This follows the logic that if you do something out of self-preservation, then you believe that you would be harmed in some way if you failed to do the task. This criterion helps establish that the task is associated with a scenario of sufficient gravity to compel vigilance.

Using these criteria, a small pilot study was performed within which two user groups were recruited and their device usage monitored for vigilance.

One user group contained situated users and the other group contained mobile users. Eight participants were selected for each group— 16 in total.

Participants were asked to maintain an online daily journal, where they described a specific session of use that occurred on that day. Over the course of two weeks, each participant logged

14 unique journal entries. A total of 224 journal entries were recorded.

Users were not directly asked if
they were being vigilant or not. Rather,
they provided details about their
usage sessions: what they were doing,
the importance of these tasks, what
prompted their usage session, and if
failure to perform the tasks would have
created any problems. A specific subset
of the responses was associated with
the vigilance criteria. If a participant’s
journal entry on any particular day
contained all of the responses that
mapped into the vigilance criteria,
then that session of use was flagged as a
vigilant one.

For the mobile group, 43. 8 percent of the recorded sessions were vigilant. For the situated group, 14. 3 percent of the recorded sessions were vigilant. Thus, mobile users were about three times more likely to be vigilant than situated users (Figure 3).

Mobile users had a higher standard deviation of 2. 6 vigilant sessions per user compared with 1. 5 for the situated users, indicating greater variance in the vigilance of mobile users. This could be because mobile devices support a greater diversity of usage scenarios, whereas situated usage was more often correlated with planned work.

There may also be more variation among mobile users in the perceived importance of monitoring the device.

For a portion of the study, users were also directly asked if they felt a need to be watchful over their devices each day.

On 78 percent of the days observed, mobile users said yes, compared with 44 percent for situated users. The ratio of daily watchfulness to vigilant sessions was 1.8: 1 for mobile users, and 3: 1 for situated users. As a measure of quality control for the study, vigilant sessions

1. Vigilant Sessions

The percentage of documented sessions that matched the vigilance criteria.

2. Watchful Days

Percentage of days that users felt the need to be watchful.

MOBILE 43.8%

14.3%

78%

SITUATED

COHORT VIGILANT SESSIONS
VIGILANCE – CORRELATION TO WATCHFULNESS
WATCHFUL
DAYS

44%

25 (78%)

14 (44%)

15

6

15

5

100%

83%

32 days
Vigilant sessions on
days where users
noted watchfulness
Vigilant sessions on
days where users felt
need to be watchful
Correlation of
vigilant sessions
and watchful days