  The proliferation of network-connected devices and applications has resulted
in people receiving dozens, or hundreds, of notifications per day. When people
are in the presence of others, each notification poses some risk of accidental
information disclosure; onlookers may see notifications appear above the lock
screen of a mobile phone, on the periphery of a desktop or laptop display, or
projected onscreen during a presentation. In this paper, we quantify the
prevalence of these accidental disclosures in the context of email
notifications, and we study people's relevant preferences and concerns. Our
results are compiled from an exploratory retrospective survey of 131
respondents, and a separate contextual-labeling study in which 169 participants
labeled 1,040 meeting-email pairs. We find that, for 53% of people, at least 1
in 10 email notifications poses an information disclosure risk. We also find
that the real or perceived severity of these risks depend both on user
characteristics and attributes of the meeting or email (e.g. the number of
recipients or attendees). We conclude by exploring machine learning algorithms
to predict people's comfort levels given an email notification and a context,
then we present implications for the design of future contextually-relevant
notification systems.
