Balancing Awareness and Interruption in Mobile Patrol using Context-Aware Notification

In mobile computing, a fundamental problem is maintaining awareness of the environment and of information presented as messages on a mobile device. In mobile police patrols, officers need to pay attention to their direct environment and stay informed of incidents elsewhere. To prevent unwanted interruption, a context-aware notification system adapts the timing and appearance of incident messages, based on user activity (available, in transit, or busy) and message priority (high, normal, or low). The authors evaluated the benefits and costs of adaptive notification compared to three uniform notification styles (presenting full messages, postponing messages or presenting indicators). Thirty-two trained student participants used a prototype notification system in a controlled mobile patrol task. The results were validated in a follow-up study with twenty-four police officers. DOI: 10.4018/jmhci.2012070101 2 International Journal of Mobile Human Computer Interaction, 4(3), 1-27, July-September 2012 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. awareness of their direct environment and of incidents elsewhere. Current notification systems in the police domain broadcast all incident messages to all officers as a central dispatcher does not know the current activity of each officer in detail. While this maintains officers’ awareness of incident messages, it can diminish awareness of the environment due to unwanted interruption. This causes officers to focus their attention inappropriately (e.g., on the device instead of on the environment) and can result in decision errors, longer response times and potentially dangerous situations. For example, a message about an illegally parked car (low priority) might be irrelevant and distracting for an officer who is just apprehending a suspect (high priority). However, to a high priority message about a colleague in danger, even officers engaged in an incident need to respond quickly. So, depending on two important context factors (message priority and officer activity), an incident message might constitute an unwanted or an appropriate interruption. This illustrates a fundamental problem in mobile human-computer interaction: the costbenefit trade-off that exists between awareness and interruption. Awareness of incident messages on a mobile device may be more important than the need to focus on the environment, requiring an interruption. On the other hand, avoiding interruption (e.g., by postponing messages) comes at the cost of delayed awareness of the message (Horvitz, Apacible, & Subramani, 2005; McCrickard & Chewar, 2003). Depending on the context (i.e., priority of the message), delayed awareness might not be a problem at all. Hence, to balance this awareness trade-off, notification systems should determine when a particular interruption is appropriate (appropriate timing) and how it should be presented (appropriate appearance) (Bailey & Konstan, 2006; McCrickard & Chewar, 2003; Streefkerk, van Esch-Bussemakers, & Neerincx, 2006). Previous research has shown that postponing, scheduling or deferring interruptions until appropriate moments mitigates the negative effects of these interruptions (Adamczyk & Bailey, 2004; Iqbal & Bailey, 2008; McFarlane, 2002). Also, the presentation modality (e.g., visually, auditorially) and salience of the message influences its interruptiveness (Kern & Schiele, 2003; Nagata, 2003; Streefkerk, van Esch-Bussemakers, & Neerincx, 2007). So in short, mobile users want to stay aware of incoming messages, but do not want to be disturbed when they are busy, unless the message is important. The level of interruption is determined by when and how a mobile device presents a message. To address this awareness-interruption trade-off, we design a context-aware notification system that adapts the notification style; i.e., the timing (e.g., postpone message) and appearance (e.g., use an indicator icon) of an incident message. The system takes into account users’ activity (available for a new incident, in transit to an incident or handling an incident) and relative priority of the message (higher, equal or lower than the current incident) at the moment of notification to determine which notification style is appropriate. This is expected to balance the awareness-interruption trade-off: limiting unwanted interruption while maintaining awareness of the environment. In this paper, we take the police domain as application domain using the following approach. First, based on previous research and context modeling in the police domain, we demonstrate that the awareness trade-off is indeed problematic in this domain. Next, we test the effects of different notification styles on the awareness trade-off in a controlled mobile experiment with non-professional participants. Finally, we validate the results of the first study with a follow-up study (previously presented at a conference) in which police officers use the same context-aware notification system in a realistic task setting. Designing for mobile professional domains, such as the police domain, requires an iterative approach in which design solutions are incrementally improved (Neerincx & Lindenberg, 2008). The first study evaluates the benefits and drawbacks of four intermediate notification style designs on task performance and the user experience. 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