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Objective: The goal of this article is to illustrate the problem-driven, cumulative, and highly interdisciplinary nature of human factors research by providing a brief overview of the work on mode errors on modern flight decks over the past two decades. Background: Mode errors on modern flight decks were first reported in the late 1980s. Poor feedback, inadequate mental models of the automation, and the high degree of coupling and complexity of flight deck systems were identified as main contributors to these breakdowns in human-automation interaction. Various improvements of design, training, and procedures were proposed to address these issues. Methods: The author describes when and why the problem of mode errors surfaced, summarizes complementary research activities that helped identify and understand the contributing factors to mode errors, and describes some countermeasures that have been developed in recent years. Results: This brief review illustrates how one particular human factors problem in the aviation domain enabled various disciplines and methodological approaches to contribute to a better understanding of, as well as provide better support for, effective human-automation coordination. Conclusion: Converging operations and interdisciplinary collaboration over an extended period of time are hallmarks of successful human factors research. Application: The reported body of research can serve as a model for future research and as a teaching tool for students in this field of work.

Objective The aim of this study was to establish the effects of simultaneous and asynchronous masking on the detection and identification of visual and auditory alarms in close temporal proximity. Background In complex and highly coupled systems, malfunctions can trigger numerous alarms within a short period of time. During such alarm floods, operators may fail to detect and identify alarms due to asynchronous and simultaneous masking. To date, the effects of masking on detection and identification have been studied almost exclusively for two alarms during single-task performance. This research examines 1) how masking affects alarm detection and identification in multitask environments and 2) whether those effects increase as a function of the number of alarms. Method Two experiments were conducted using a simulation of a drone-based package delivery service. Participants were required to ensure package delivery and respond to visual and auditory alarms associated with eight drones. The alarms were presented at various stimulus onset asynchronies (SOAs). The dependent measures included alarm detection rate, identification accuracy, and response time. Results Masking was observed intramodally and cross-modally for visual and auditory alarms. The SOAs at which asynchronous masking occurred were longer than reported in basic research on masking. The effects of asynchronous and, even more so, simultaneous masking became stronger as the number of alarms increased. Conclusion Masking can lead to breakdowns in the detection and identification of alarms in close temporal proximity in complex data-rich domains. Application The findings from this research provide guidance for the design of alarm systems.

Objective: The objective was to use eye tracking to trace the underlying changes in attention allocation associated with the performance effects of clutter, stress, and task difficulty in visual search and noticing tasks. Background: Clutter can degrade performance in complex domains, yet more needs to be known about the associated changes in attention allocation, particularly in the presence of stress and for different tasks. Frequently used and relatively simple eye tracking metrics do not effectively capture the various effects of clutter, which is critical for comprehensively analyzing clutter and developing targeted, real-time countermeasures. Method: Electronic medical records (EMRs) were chosen as the application domain for this research. Clutter, stress, and task difficulty were manipulated, and physicians' performance on search and noticing tasks was recorded. Several eye tracking metrics were used to trace attention allocation throughout those tasks, and subjective data were gathered via a debriefing questionnaire. Results: Clutter degraded performance in terms of response time and noticing accuracy. These decrements were largely accentuated by high stress and task difficulty. Eye tracking revealed the underlying attentional mechanisms, and several display-independent metrics were shown to be significant indicators of the effects of clutter. Conclusion: Eye tracking provides a promising means to understand in detail (offline) and prevent (in real time) major performance breakdowns due to clutter. Application: Display designers need to be aware of the risks of clutter in EMRs and other complex displays and can use the identified eye tracking metrics to evaluate and/or adjust their display.

Objective: We aimed to synthesize the literature on display clutter by reviewing definitions and measurement techniques and to develop a comprehensive, ergonomics-oriented perspective on clutter. We provide guidance for the selection of measurement approaches that can capture the various aspects and effects of clutter on visual search in particular. Background: There is agreement that clutter may represent a significant problem to operators. The challenge is to determine the ideal middle ground between excessive data and insufficient information. However, definitions of clutter vary widely, which explains the range of measurement approaches, including image-processing algorithms, performance evaluation, subjective evaluation, and eye tracking. It is important to understand the affordances of each technique and provide guidance for their use. Method: We provide a systematic review of clutter definitions and develop a performance-oriented perspective for ergonomics research. Next, we present a critical overview of clutter measurement approaches. The benefits and limitations of each technique are detailed, and recommendations for best practice are provided. Results: From an ergonomics perspective, clutter matters to the extent that it affects performance, particularly, visual search. A combination of measurement techniques can be employed in order to assess the performance costs stemming from the multiple aspects of clutter. Conclusion: Display clutter is a multifaceted construct that is a problem when it results in performance and attentional costs. The assessment of these costs is critical and requires the use of appropriate and complementary techniques. Application: It is important that the performance costs of clutter are detected reliably to be able to better support attention management.

Objective: The present study examined whether tactile change blindness and crossmodal visual-tactile change blindness occur in the presence of two transient types and whether their incidence is affected by the addition of a concurrent task. Background: Multimodal and tactile displays have been proposed as a promising means to overcome data overload and support attention management. To ensure the effectiveness of these displays, researchers must examine possible limitations of human information processing, such as tactile and crossmodal change blindness. Method: Twenty participants performed a unmanned aerial vehicle (UAV) monitoring task that included visual and tactile cues. They completed four blocks of 70 trials each, one involving visual transients, the other tactile transients. A search task was added to determine whether increased workload leads to a higher risk of change blindness. Results: The findings confirm that tactile change detection suffers in terms of response accuracy, sensitivity, and response bias in the presence of a tactile transient. Crossmodal visual-tactile change blindness was not observed. Also, change detection was not affected by the addition of the search task and helped reduce response bias. Conclusion: Tactile displays can help support multitasking and attention management, but their design needs to account for tactile change blindness. Simultaneous presentation of multiple tactile indications should be avoided as it adversely affects change detection. Application: The findings from this research will help inform the design of multimodal and tactile interfaces in data-rich domains, such as military operations, aviation, and healthcare.

ObjectiveThis research sought to determine whether people can perceive and process three nonredundant (and unrelated) signals in vision, hearing, and touch at the same time and how aging and concurrent task demands affect this ability.BackgroundMultimodal displays have been shown to improve multitasking and attention management; however, their potential limitations are not well understood. The majority of studies on multimodal information presentation have focused on the processing of only two concurrent and, most often, redundant cues by younger participants.MethodTwo experiments were conducted in which younger and older adults detected and responded to a series of singles, pairs, and triplets of visual, auditory, and tactile cues in the absence (Experiment 1) and presence (Experiment 2) of an ongoing simulated driving task. Detection rates, response times, and driving task performance were measured.ResultsCompared to younger participants, older adults showed longer response times and higher error rates in response to cues/cue combinations. Older participants often missed the tactile cue when three cues were combined. They sometimes falsely reported the presence of a visual cue when presented with a pair of auditory and tactile signals. Driving performance suffered most in the presence of cue triplets.ConclusionPeople are more likely to miss information if more than two concurrent nonredundant signals are presented to different sensory channels.ApplicationThe findings from this work help inform the design of multimodal displays and ensure their usefulness across different age groups and in various application domains.

Objective: The goal of the present study was to develop and empirically evaluate three countermeasures to tactile change blindness (where a tactile signal is missed in the presence of a tactile transient). Each of these countermeasures relates to a different cognitive step involved in successful change detection. Background: To date, change blindness has been studied primarily in vision, but there is limited empirical evidence that the tactile modality may also be subject to this phenomenon. Change blindness raises concerns regarding the robustness of tactile and multimodal interfaces. Method: Three countermeasures to tactile change blindness were evaluated in the context of a highly demanding monitoring task. One countermeasure was proactive (alerting the participant to a possible change before it occurred) whereas the other two were adaptive (triggered after the change upon an observed miss). Performance and subjective data were collected. Results: Compared to the baseline condition, all countermeasures improved intramodal tactile change detection. Adaptive measures resulted in the highest detection rates, specifically when signal gradation was employed (i.e., when the intensity of the tactile signal was increased after a miss was observed). Conclusion: Adaptive displays can be used to counter the effects of change blindness and ensure that tactile information is reliably detected. Increasing the tactile intensity after a missed change appears most promising and was the preferred countermeasure. Application: The findings from this study can inform the design of interfaces employing the tactile modality to support monitoring and attention management in data-rich domains.

Objective: A novel vibrotactile display type was investigated to determine the potential benefits for supporting the attention and task management of anesthesiologists. Background: Recent research has shown physiological monitoring and multitasking performance can benefit from displaying patient data via alarm-like tactile notifications and via continuously informing auditory displays (e.g., sonifications). The current study investigated a novel combination of these two approaches: continuously informing tactile displays. Method: A tactile alarm and two continuously informing tactile display designs were evaluated in an anesthesia induction simulation with anesthesiologists as participants. Several performance measures were collected for two tasks: physiological monitoring and anesthesia induction. A multi-task performance score equivalently weighted components from each task, normalized across experimental scenarios. Subjective rankings of the displays were also collected. Results: Compared to the baseline (visual and auditory only) display configuration, each tactile display significantly improved performance in several objective measures, including multitask performance score. The continuously informing display that encoded the severity of patient health into the salience of its signals supported significantly better performance than the other two tactile displays. Contrasting the objective results, participants subjectively ranked the tactile alarm display highest. Conclusion: Continuously informing tactile displays with alarm-like properties (e.g., salience mapping) can better support anesthesiologists' physiological monitoring and multitasking performance under the high task demands of anesthesia induction. Adaptive display mechanisms may improve user acceptance. Application: This study can inform display design to support multitasking performance of anesthesiologists in the clinical setting and other supervisory control operators in work domains characterized by high demands for visual and auditory resources.

Objective: This article provides an overview of tactile displays. Its goal is to assist human factors practitioners in deciding when and how to employ the sense of touch for the purpose of information representation. The article also identifies important research needs in this area. Background: First attempts to utilize the sense of touch as a medium for communication date back to the late 1950s. For the next 35 years progress in this area was relatively slow, but recent years have seen a surge in the interest and development of tactile displays and the integration of tactile signals in multimodal interfaces. A thorough understanding of the properties of this sensory channel and its interaction with other modalities is needed to ensure the effective and robust use of tactile displays. Methods: First, an overview of vibrotactile perception is provided. Next, the design of tactile displays is discussed with respect to available technologies. The potential benefit of including tactile cues in multimodal interfaces is discussed. Finally, research needs in the area of tactile information presentation are highlighted. Results: This review provides human factors researchers and interface designers with the requisite knowledge for creating effective tactile interfaces. It describes both potential benefits and limitations of this approach to information presentation. Conclusion: The sense of touch represents a promising means of supporting communication and coordination in human-human and human-machine systems. Application: Tactile interfaces can support numerous functions, including spatial orientation and guidance, attention management, and sensory substitution, in a wide range of domains.

Operators in high-risk domains such as aviation often need to make decisions under time pressure and uncertainty. One way to support them in this task is through the introduction of decision support systems (DSSs). The present study examined the effectiveness of two different DSS implementations: status and command displays. Twenty-seven pilots (9 pilots each in a baseline, status, and command group) flew 20 simulated approaches involving icing encounters. Accuracy of the decision aid (a smart icing system), familiarity with the icing condition, timing of icing onset, and autopilot usage were varied within subjects. Accurate information from either decision aid led to improved handling of the icing encounter. However, when inaccurate information was presented, performance dropped below that of the baseline condition. The cost of inaccurate information was particularly high for command displays and in the case of unfamiliar icing conditions. Our findings suggest that unless perfect reliability of a decision aid can be assumed, status displays may be preferable to command displays in high-risk domains (e.g., space flight, medicine, and process control), as the former yield more robust performance benefits and appear less vulnerable to automation biases.

This study examined the effects of conflict type, time pressure, and display design on operators' ability to make informed decisions about proposed machine goals and actions in a management-by-consent context. A group of 30 B757 pilots were asked to fly eight descent scenarios while responding to a series of air traffic control clearances. Each scenario presented pilots with a different conflict that arose from either incompatible goals contained in the clearance or inappropriate implementation of the clearance by automated flight deck systems. Pilots were often unable to detect these conflicts, especially under time pressure, and thus failed to disallow or intervene with proposed machine actions. Detection performance was particularly poor for conflicts related to clearance implementation. These conflicts were most likely to be missed when automated systems did more than the pilot expected of them. Performance and verbal protocol data indicate that the observed difficulties can be explained by a combination of poor system feedback and pilots' difficulties with generating expectations of future system behavior. Our results are discussed in terms of their implications for the choice and implementation of automation management strategies in general and, more specifically, with respect to risks involved in envisioned forms of digital air-ground communication in the future aviation system. Actual or potential applications of this research include the design of future data link systems and procedures, as well as the design of future automated systems in any domain that rely on operator consent as a mechanism for human-machine coordination.

Objectives: This study sought to determine whether performance effects of crossmodal spatial links that were observed in earlier laboratory studies scale to more complex environments and need to be considered in multimodal interface design. It also revisits the unresolved issue of cross-modal cuing asymmetries. Background: Previous laboratory studies employing simple cues, tasks, and/or targets have demonstrated that the efficiency of processing visual, auditory, and tactile stimuli is affected by the modality, lateralization, and timing of surrounding cues. Very few studies have investigated these cross-modal constraints in the context of more complex environments to determine whether they scale and how complexity affects the nature of crossmodal cuing asymmetries. Method: A microworld simulation of battlefield operations with a complex task set and meaningful visual, auditory, and tactile stimuli was used to investigate cuing effects for all cross-modal pairings. Results: Significant asymmetric performance effects of cross-modal spatial links were observed. Auditory cues shortened response latencies for collocated visual targets but visual cues did not do the same for collocated auditory targets. Responses to contralateral (rather than ipsilateral) targets were faster for tactually cued auditory targets and each visual-tactile cue-target combination, suggesting an inhibition-of-return effect. Conclusions: The spatial relationships between multimodal cues and targets significantly affect target response times in complex environments. The performance effects of cross-modal links and the observed cross-modal cuing asymmetries need to be examined in more detail and considered in future interface design. Application: The findings from this study have implications for the design of multimodal and adaptive interfaces and for supporting attention management in complex, data-rich domains.

Objective: To examine operator strategies for diagnosing and recovering from errors and disturbances as well as the impact of automation design and time pressure on these processes. Background: Considerable efforts have been directed at error prevention through training and design. However, because errors cannot be eliminated completely, their detection, diagnosis, and recovery must also be supported. Research has focused almost exclusively on error detection. Little is known about error diagnosis and recovery, especially in the context of event-driven tasks and domains. Method: With a confederate pilot, 12 airline pilots flew a 1-hr simulator scenario that involved three challenging automation-related tasks and events that were likely to produce erroneous actions or assessments. Behavioral data were compared with a canonical path to examine pilots' error and disturbance management strategies. Debriefings were conducted to probe pilots' system knowledge. Results: Pilots seldom followed the canonical path to cope with the scenario events. Detection of a disturbance was often delayed. Diagnostic episodes were rare because of pilots' knowledge gaps and time criticality. In many cases, generic inefficient recovery strategies were observed, and pilots relied on high levels of automation to manage the consequences of an error. Conclusion. Our findings describe and explain the nature and shortcomings of pilots' error management activities. They highlight the need for improved automation training and design to achieve more timely detection, accurate explanation, and effective recovery from errors and disturbances. Application: Our findings can inform the design of tools and techniques that support disturbance management in various complex, event-driven environments.

Objective: To examine whether continually updated information about a system's confidence in its ability to perform assigned tasks improves operators' trust calibration in, and use of, an automated decision support system (DSS). Background: The introduction of decision aids often leads to performance breakdowns that are related to automation bias and trust miscalibration. This can be explained, in part, by the fact that operators are informed about overall system reliability only, which makes it impossible for them to decide on a case-by-case basis whether to follow the system's advice. Method: The application for this research was a neural net-based decision aid that assists pilots with detecting and handling in-flight icing encounters. A multifactorial experiment was carried out with two groups of 15 instructor pilots each flying a series of 28 approaches in a motion-base simulator. One group was informed about the system's overall reliability only, whereas the other group received updated system confidence information. Results: Pilots in the updated group experienced significantly fewer icing-related stalls and were more likely to reverse their initial response to an icing condition when it did not produce desired results. Their estimate of the system's accuracy was more accurate than that of the fixed group. Conclusion: The presentation of continually updated system confidence information can improve trust calibration and thus lead to better performance of the human-machine team. Application: The findings from this research can inform the design of decision support systems in a variety of event-driven high-tempo domains.