Duncan P. Brumby

iPod distraction: effects of portable music-player use on driver performance

Portable music players such as Apples iPod have become ubiquitous in many environments, but one environment in particular has elicited new safety concerns and challenges -- in-vehicle use while driving. We present the first study of portable music-player interaction while driving, examining the effects of iPod interaction by drivers navigating a typical roadway in a driving simulator. Results showed that selecting media on the iPod had a significant effect on driver performance as measured by lateral deviation from lane center; the effect was comparable to previously reported effects of dialing a cellular phone. In addition, selecting media and watching videos had a significant effect on car-following speed, resulting in speed reductions that presumably compensated for impaired lateral performance. Given that iPod interaction has become increasingly common while driving, these results serve as a first step toward understanding the potential effects of portable music-player interaction on driver behavior and performance.

Recovering from an interruption: Investigating speed−accuracy trade-offs in task resumption behavior.

Interruptions are disruptive because they take time to recover from, in the form of a resumption lag, and lead to an increase in the likelihood of errors being made. Despite an abundance of work investigating the effect of interruptions on routine task performance, little is known about whether there is a link between how quickly a task is resumed following an interruption (i.e., the duration of the postinterruption resumption lag) and the likelihood that an error is made. Two experiments are reported in which participants were interrupted by a cognitively demanding secondary mental arithmetic task while working on a routine sequential data-entry task. In Experiment 1 the time-cost of making an error on the primary task was varied between conditions. When errors were associated with a high time-cost penalty, participants made fewer errors and resumed the primary task more slowly than when errors were associated with a low time-cost penalty. In Experiment 2 participants were prohibited from resuming the primary task quickly by a 10-s system lockout period following the completion of the interrupting task. This lockout period led to a significant reduction in resumption errors because the lockout prohibited fast, inaccurate task resumptions. Taken together, our results suggest that longer resumption lags following an interruption are beneficial in terms of reducing the likelihood of errors being made. We discuss the practical implications of how systems might be designed to encourage more reflective task resumption behavior in situations where interruptions are commonplace. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Focus on driving: how cognitive constraints shape the adaptation of strategy when dialing while driving

We investigate how people adapt their strategy for interleaving multiple concurrent tasks to varying objectives. A study was conducted in which participants drove a simulated vehicle and occasionally dialed a telephone number on a mobile phone. Experimental instructions and feedback encouraged participants to focus on either driving or dialing. Results show that participants adapted their task interleaving strategies to meet the required task objective, but in a manner that was nonetheless intricately shaped by internal psychological constraints. In particular, participants tended to steer in between dialing chunks of digits even when extreme vehicle drift implied that more reactive strategies would have generated better lane keeping. To better understand why drivers interleaved tasks at chunk boundaries, a modeling analysis was conducted to derive performance predictions for a range of dialing strategies. The analysis supported the idea that interleaving at chunk boundaries efficiently traded the time given up to dialing with the maintenance of a central lane position. We discuss the implications of this work in terms of contributions to understanding how cognitive constraints shape strategy adaptations in dynamic multitask environments.

Strategies for guiding interactive search: An empirical investigation into the consequences of label relevance for assessment and selection

ABSTRACT When searching a novel Web page, people often estimate the likelihood that labeled links on the page will lead to their goal. A rational analysis of this activity suggests that people should adjust their estimate of the likelihood that any one item will lead to the goal in a manner that is sensitive to the context provided by the likelihoods that other items on the page will lead to the goal. Two experiments were designed to provide evidence to discriminate between this account and others found in the literature (e.g., satisficing and assess-all accounts). The experiments systematically manipulated the relevance of the distractor items and the location of the target item on the page. The results showed that (a) a high-value item was more likely to be selected when it was first encountered if the relevance of competing distractors was relatively low and (b) more items were assessed prior to selection when the distractors were of greater semantic relevance to the goal. The location manipulation showed that if more distractors were assessed prior to the target item, then the relevance of the distractors had a greater influence on the decision as to whether to select the target immediately. These results suggest that decisions as to when to select an item from the page are sensitive to the context provided by the likelihoods of all of the items so far assessed and not just to the most recent item. The findings are therefore inconsistent with both satisficing and assess-all accounts of interactive search.

Strategic Adaptation to Performance Objectives in a Dual­Task Setting

How do people interleave attention when multitasking? One dominant account is that the completion of a subtask serves as a cue to switch tasks. But what happens if switching solely at subtask boundaries led to poor performance? We report a study in which participants manually dialed a UK-style telephone number while driving a simulated vehicle. If the driver were to exclusively return his or her attention to driving after completing a subtask (i.e., using the single break in the xxxxx-xxxxxx representational structure of the number), then we would expect to see a relatively poor driving performance. In contrast, our results show that drivers choose to return attention to steering control before the natural subtask boundary. A computational modeling analysis shows that drivers had to adopt this strategy to meet the required performance objective of maintaining an acceptable lateral position in the road while dialing. Taken together these results support the idea that people can strategically control the allocation of attention in multitask settings to meet specific performance criteria.

Natural Break Points The Influence of Priorities and Cognitive and Motor Cues on Dual-Task Interleaving

What factors determine when people interleave tasks when multitasking? Here the authors look at the role of priorities and cognitive and motor cues. A study was conducted in which participants steered a simulated vehicle while also dialing two phone numbers that contained sets of repeating digits. Participants tended to interleave tasks after typing in a complete set of repeating digits and sometimes also at the cognitive chunk boundary. The exact pattern of how participants interleaved these tasks depended on their priority objective. A modeling analysis that explored performance for a series of alternative strategies for task interleaving, given the cognitive and task constraints, suggested why participants avoided interleaving at other points: Such strategies tend to move performance away from a trade-off curve that strikes an optimal balance between dialing and driving performance. The study highlights the role that cognitive and motor cues can play in dual-task performance and the importance of being aware, and acting on, priorities. Further implications and limitations are discussed.

Smart Citizen Sentiment Dashboard: A Case Study Into Media Architectural Interfaces

In this paper we introduce the notion of media architectural interfaces (MAIs), which describe the relation between users engaging with dynamic content on media façades through tangible artifacts on street level. Firstly, we outline existing research concerned with public displays, urban screens and media facades, secondly we summarize related works that explore mediated urban interactions in connection with MAIs. We report on the technical set up of a field study, in which we deployed a novel tangible user interface (TUI), called the Smart Citizen Sentiment Dashboard (SCSD). This device gives citizens the opportunity to express their mood about local urban challenges. The input from this TUI is then instantly displayed on a very large (3700 sqm) media façade. The installation ran for three weeks during a media arts festival in Sao Paulo, Brazil. During this deployment period, we were able to gather data to help us understand the relationship between passers-by, participants, the TUI and the media façade. As a result we identified emergent behavior in the immediate space around the TUI and the wider urban space. The contribution this paper makes is in highlighting challenges in the design and deployment of large-scale media architectural interfaces.

Fast or safe?: how performance objectives determine modality output choices while interacting on the move

In-car devices that use audio output have been shown to be less distracting than traditional graphical user interfaces, but can be cumbersome and slow to use. In this paper, we report an experiment that demonstrates how these performance characteristics impact whether people will elect to use an audio interface in a multitasking situation. While steering a simulated vehicle, participants had to locate a source of information in a short passage of text. The text was presented either on a visual interface, or using a text-to-speech audio interface. The relative importance of each task was varied. A no-choice/choice paradigm was used in which participants first gained experience with each of the two interfaces, before being given a choice on which interface to use on later trials. The characteristics of the interaction with the interfaces, as measured in the no-choice phase, and the relative importance of each task, had an impact on which output modality was chosen in the choice phase. Participants that prioritized the secondary task tended to select the (faster yet more distracting) visual interface over the audio interface, and as a result had poorer lane keeping performance. This work demonstrates how a users task objective will influence modality choices with multimodal devices in multitask environments.

A cognitive constraint model of dual-task trade-offs in a highly dynamic driving task

The paper describes an approach to modeling the strategic variations in performing secondary tasks while driving. In contrast to previous efforts that are based on simulation of a cognitive architecture interacting with a task environment, we take an approach that develops a cognitive constraint model of the interaction between the driver and the task environment in order to make inferences about dual-task performance. Analyses of driving performance data reveal that a set of simple equations can be used to accurately model changes in the lateral position of the vehicle within the lane. The model quantifies how the vehicles deviation from lane center increases during periods of inattention, and how the vehicle returns to lane center during periods of active steering. We demonstrate the benefits of the approach by modeling the dialing of a cellular phone while driving, where drivers balance the speed in performing the dial task with accuracy (or safety) in keeping the vehicle centered in the roadway. In particular, we show how understanding, rather than simulating, the constraints imposed by the task environment can help to explain the costs and benefits of a range of strategies for interleaving dialing and steering. We show how particular strategies are sensitive to a combination of internal constraints (including switch costs) and the trade-off between the amount of time allocated to secondary task and the risk of extreme lane deviation.

Interrupted by a phone call: exploring designs for lowering the impact of call notifications for smartphone users

Mobile phones have evolved significantly in recent years from single-purpose communication devices to multi-purpose computing devices. Despite this evolution, the interaction model for how incoming calls are handled has barely changed. Current-generation smartphones still use abrupt full-screen notifications to alert users to incoming calls, demanding a decision to either accept or decline the call. These full-screen notifications forcibly interrupt whatever activity the user was already engaged in. This might be undesirable when the users primary task was more important than the incoming call. This paper explores the design space for how smartphones can alert users to incoming calls. We consider designs that allow users to postpone calls and also to multiplex by way of a smaller partial-screen notification. These design alternatives were evaluated in both a small-scale controlled lab study as well as a large-scale naturalistic in-the-wild study. Results show that a multiplex design solution works best because it allows people to continue working on their primary task while being made aware that there is a caller on the line. The contribution of this work is an enhanced interaction design for handling phone calls, and an understanding of how people use it for handling incoming calls.