Human Factors: The Journal of the Human Factors and Ergonomics Society recent issues

Socializing the Human Factors Analysis and Classification System: Incorporating Social Psychological Phenomena Into a Human Factors Error Classification System

Paletz, S. B. F., Bearman, C., Orasanu, J., Holbrook, J. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: The presence of social psychological pressures on pilot decision making was assessed using qualitative analyses of critical incident interviews. Background: Social psychological phenomena have long been known to influence attitudes and behavior but have not been highlighted in accident investigation models. Method: Using a critical incident method, 28 pilots who flew in Alaska were interviewed. The participants were asked to describe a situation involving weather when they were pilot in command and found their skills challenged. They were asked to describe the incident in detail but were not explicitly asked to identify social pressures. Pressures were extracted from transcripts in a bottom-up manner and then clustered into themes. Results: Of the 28 pilots, 16 described social psychological pressures on their decision making, specifically, informational social influence, the foot-in-the-door persuasion technique, normalization of deviance, and impression management and self-consistency motives. Conclusion: We believe accident and incident investigations can benefit from explicit inclusion of common social psychological pressures. Application: We recommend specific ways of incorporating these pressures into the Human Factors Analysis and Classification System.

False Alerts in Air Traffic Control Conflict Alerting System: Is There a "Cry Wolf" Effect?

Wickens, C. D., Rice, S., Keller, D., Hutchins, S., Hughes, J., Clayton, K. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: The aim is to establish the extent to which the high false-alarm rate of air traffic control midair conflict alerts is responsible for a "cry wolf" effect—where true alerts are not responded to and all alerts are delayed in their response. Background: Some aircraft collisions have been partly attributed to the cry wolf effect, and in other domains (health care and systems monitoring), there is a causal connection between false-alarm rate and cry wolf behavior. We hypothesized that a corresponding relationship exists in air traffic control (ATC). Method: Aircraft track and alert system behavior data surrounding 495 conflict alerts were analyzed to identify true and false alerts, trajectory type, and controller behavior. Forty-five percent of the alerts were false, ranging from 0.28 to 0.58. Results: Although centers with more false alerts contributed to more nonresponses, there was no evidence that these were nonresponses to true alerts or that response times were delayed in those centers. Instead, controllers showed desirable anticipatory behavior by issuing trajectory changes prior to the alert. Those trajectory pairs whose conflicts were more difficult to visualize induced more reliance on, and less compliance with, the alerting system. Conclusion: The high false-alarm rate does not appear to induce cry wolf behavior in the context of en route ATC conflict alerts. Application: There is no need to substantially modify conflict alert algorithms, but the conflict alert system may be modified to address difficult-to-visualize conflicts.

Effects of In-Car Support on Mental Workload and Driving Performance of Older Drivers

Davidse, R. J., Hagenzieker, M. P., van Wolffelaar, P. C., Brouwer, W. H. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: This study examined the extent to which driving performance of 10 older (70—88 years old) and 30 younger participants (30—50 years old) improves as a result of support by a driver assistance system. Background: Various studies have indicated that advanced driver assistance systems (ADAS) may provide tailored assistance for older drivers and thereby improve their safe mobility. Method: While drivers followed an urban route in a driving simulator, an ADAS provided them with prior knowledge on the next intersection. The system was evaluated in terms of effects on workload and safety performance. Results: Messages informing drivers about the right-of-way regulation, obstructed view of an intersection, and safe gaps to join or cross traffic streams led to safer driving performance. A message regarding an unexpected one-way street led to fewer route errors. In general, effects were the same for all age groups. Workload was not reduced by the support system. Conclusion: The evaluated support system shows promising effects for all age groups. Longer evaluation periods are needed to determine long-term effects. Application: The messages provided by the evaluated system are currently not provided by existing ADAS such as advanced cruise control and navigation systems, but they could possibly be added to them in the future.

Effects of Human--Machine Competition on Intent Errors in a Target Detection Task

Beck, H. P., McKinney, J. B., Dzindolet, M. T., Pierce, L. G. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: This investigation examined the impact of human—machine competition (John Henry effects) on intent errors. John Henry effects, expressed as an unwillingness to use automation, were hypothesized to increase as a function of operators’ personal investment in unaided performance. Background: Misuse and disuse often occur because operators (a) cannot determine if automation or a nonautomated alternative maximizes the likelihood of task success (appraisal errors) or (b) know the utilities of the options but disregard this information when deciding to use or not to use automation (intent errors). Although appraisal errors have been extensively studied, there is a paucity of information regarding the causes and prevention of intent errors. Methods: Operators were told how many errors they and an automated device made on a target detection task. Self-reliant operators (high personal investment) could depend on their performance or automation to identify a target. Other-reliant operators (low personal investment) could rely on another person or automation. Results: As predicted, self-reliance increased disuse and decreased misuse. Conclusion: When the disuse and misuse data are viewed together, they strongly support the supposition that personal investment in unaided performance affects the likelihood of John Henry effects and intent errors. Application: These results demonstrate the need for a model of operator decision making that takes into account intent as well as appraisal errors. Potential applications include developing interventions to counter the deleterious effects of human—machine competition and intent errors on automation usage decisions.

Height of Industrial Hand Wheel Valves Affects Torque Exertion

Wieszczyk, S. M., Marklin, R. W., Sanchez, H. J. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: The aim of this study was to determine how height of a hand wheel affects maximum torque production and risk of injury to the shoulders and back of workers. Background: Workers in the processing, refinery, and energy generation industries manually open and close valves with hand wheels that require high torque. This task is physically strenuous and can lead to shoulder musculoskeletal disorders (MSDs). Method: Maximum torque exertions in the clockwise and counterclockwise directions at three heights (knee, chest, and overhead) were tested. Results: The torque production in the counterclockwise (left) direction was greater than that of the clockwise (right) direction (150.5 N·m vs. 141 N·m). This main effect was independent of valve height, as there was no interaction between direction and valve height (p = .686). Participants exerted at least 10% greater torque at the overhead level than at the chest level (means of 153.2 N·m vs. 138.3 N·m). There was no difference in maximum torque between knee and overhead levels and between knee and chest levels. Conclusion: According to ergonomics principles, the risk of MSDs affecting the shoulder and trunk from turning valves should be lowest at chest height because the postures of the shoulder and trunk are at or near neutral. However, workers exerted greatest torque when the valve was located overhead. Whether valves located at overhead height, compared with chest height, present greater risk of MSDs to workers is not known. Application: Design engineers should avoid placing hand wheel valves at knee height or lower.

Harness Sizing and Strap Length Configurations

Hsiao, H., Whitestone, J., Taylor, S., Godby, M., Guan, J. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: This article describes the derivation of strap lengths and adjustments to fall-arrest harnesses and the development of harness size configurations. Background: Updated harness sizing configurations are needed to accommodate diverse populations in the current workforce. Method: Three-dimensional torso anthropometric data from 243 women and 258 men were incorporated into eight validated equations to develop a cost-effective harness sizing plan and to define strap lengths. Results: To met strap adjustable range goals and to accommodate 95% to 98% of the estimated population, two sizing options were identified. Conclusion: Study outcomes suggest system improvement with three to four sizes for women and three to four sizes for men, on which the adjustment ranges of the torso straps were within 15 to 17 cm and within 20 to 23 cm on thigh and hip straps. Application: This research provided harness sizing and cut-length information for harness design to reduce the risk of worker injury that results from poor fit or improper size selection.

Improving Extreme-Scale Problem Solving: Assessing Electronic Brainstorming Effectiveness in an Industrial Setting

Dornburg, C. C., Stevens, S. M., Hendrickson, S. M. L., Davidson, G. S. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: An experiment was conducted to compare the effectiveness of individual versus group electronic brainstorming to address difficult, real-world challenges. Background: Although industrial reliance on electronic communications has become ubiquitous, empirical and theoretical understanding of the bounds of its effectiveness have been limited. Previous research using short-term laboratory experiments have engaged small groups of students in answering questions irrelevant to an industrial setting. The present experiment extends current findings beyond the laboratory to larger groups of real-world employees addressing organization-relevant challenges during the course of 4 days. Methods: Employees and contractors at a national laboratory participated, either in a group setting or individually, in an electronic brainstorm to pose solutions to a real-world problem. Results: The data demonstrate that (for this design) individuals perform at least as well as groups in producing quantity of electronic ideas, regardless of brainstorming duration. However, when judged with respect to quality along three dimensions (originality, feasibility, and effectiveness), the individuals significantly (p < .05) outperformed the group. Conclusion: When quality is used to benchmark success, these data indicate that work-relevant challenges are better solved by aggregating electronic individual responses rather than by electronically convening a group. Application: This research suggests that industrial reliance on electronic problem-solving groups should be tempered, and large nominal groups may be more appropriate corporate problem-solving vehicles.

Feedback Preferences and Impressions of Waiting

Branaghan, R. J., Sanchez, C. A. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: Three experiments examined the effects of various feedback displays on user preference, apparent waiting durations, waiting time reasonableness, and other user experience measures. Background: User interface guidelines advocate keeping users informed about system status; however, the duration estimation literature shows that focusing on temporal information makes the wait seem longer. How can designers reconcile these issues? Methods: In three experiments, students chose movies from a simulated movie database and then were shown feedback displays (static, sequential dots, constant-rate progress bars, or variable-rate progress bars) for different durations. Users judged how reasonable the wait was and how long it lasted and then ranked their preference for the dialogs. Results: The pattern of preference results was different from duration-related judgments. Users preferred feedback that provided more information. On the other hand, when judging duration, users perceived simpler interfaces as being most reasonable. Conclusion: Different types of feedback are required for reducing perceived wait and increasing preference. Ratings of wait time reasonableness were consistent with the attentional gate theory of prospective timing; attention-demanding activity caused the wait to seem less reasonable. Preference, on the other hand, requires keeping users informed about the progress of operations. Application: Users prefer more feedback rather than less, even if it makes the wait seem less reasonable. However, the constant progress bar performed at the top of both reasonableness and preference, keeping users informed without increasing arousal or focusing attention on temporal stimuli. Other options are also discussed to make duration perceptions more reasonable.

Using Peripersonal Warning Signals to Orient a Driver's Gaze

Ho, C., Spence, C. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: We report a series of three experiments designed to assess the relative speed with which people can initiate speeded head-orienting responses following the presentation of spatial warning signals. Background: Recent cognitive neuroscience findings have shown that the human brain tends to treat stimuli occurring in peripersonal space as being somehow more behaviorally relevant and attention demanding than stimuli occurring in extrapersonal space. These brain mechanisms may be exploited in the design of warning signals. Method: Experiment 1 assessed the effectiveness of various different unisensory warning signals in eliciting a head-turning response to look at the potential source of danger requiring participants’ immediate attention; Experiment 2 assessed the latency of a driver’s responses to events occurring in the cued direction; Experiment 3 assessed the relative effectiveness of various warning signals in reorienting a person’s gaze back to a central driving task while he or she was distracted by a secondary task. Results: The results show that participants initiated head-turning movements and made speeded discrimination or braking responses significantly more rapidly following the presentation of a close rear auditory warning signal than following the presentation of either a far frontal auditory warning signal, a vibrotactile warning signal presented to their waist, or a peripheral visual warning signal. Conclusion: These results support the claim that the introduction of peripersonal warning signals results in a significant performance advantage relative to traditionally designed warnings. Application: Warning systems that have been designed around the constraints of the human brain offer great potential in the future design of multisensory interfaces.

Perception of Robot Passability With Direct Line of Sight and Teleoperation

Moore, K. S., Gomer, J. A., Pagano, C. C., Moore, D. D. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: To examine participants’ abilities to judge the passability of robots through apertures in direct-line-of-sight (DLS) and teleoperation (TO) conditions, two experiments were conducted. Background: Past work has demonstrated that operators find it difficult to perceive aspects of remote environments during TO. For example, urban search-and-rescue operators have experienced difficulty judging whether a robot could pass through openings or over obstacles. Although previous research has discussed perceptual difficulties in TO, the differences between DLS and TO have not been quantified. Method: In the first experiment, participants judged the smallest passable aperture widths for three robot sizes for both DLS and TO conditions. In the second experiment, aperture widths were judged for three camera heights and two robot distances during TO. Results: In the DLS condition, participants produced similar judgments for the three robot sizes using dimensionless measurements. In the TO condition, participants’ judgments were more variable and they judged smaller apertures as passable. Conclusion: Overall, participants judged apertures that were too small for the robot to pass as passable. This tendency was more pronounced in four instances: as robot size increased, during TO, when the camera was at its lowest height, and as distance between the robot and the aperture increased. Application: Judgments of passability help to quantify differences in perception between DLS and TO. These results will be useful in the design of training regimes for TO tasks. Increasing operator understanding of performance differences under varying conditions will lead them to be more accurate when making critical decisions in remote environments.

Effects of a Computer-Based Training Module on Drivers' Willingness to Engage in Distracting Activities

Horrey, W. J., Lesch, M. F., Kramer, A. F., Melton, D. F. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: This study examines the effect of a computer-based training module on drivers’ attitudes and behaviors with respect to in-vehicle distraction. Background: Research findings on the negative performance implications of distraction call for the need to mitigate these adverse effects. Method: Forty drivers (ages 18 to 20 yrs) were divided into two groups: a training group that completed the module and a control group that viewed an unrelated video. The training promoted enhanced metacognitive skills (e.g., planning, monitoring) and strategies to deal with distraction. Measures of willingness to perform in-vehicle activities while driving (involving the use of short videos) were assessed before and after the intervention. Drivers also performed in-vehicle tasks while driving an instrumented vehicle on a closed test track. Results: Following the training, drivers in the training group showed a decline in their ratings of willingness to engage in distracting activities along with a corresponding increase in perceived risk. In contrast, ratings from drivers in the control group did not change on any measures. Drivers in the training group were also more likely to perform in-vehicle tasks while the vehicle was parked compared with the control group—an obvious safety benefit. However, there was no observable benefit of training for drivers who performed the distracting tasks while the vehicle was in motion. Conclusion: There may be some promise to such a training approach. The implications for distraction and training are discussed. Application: Training general skills in dealing with potentially distracting in-vehicle tasks may help offset some of the negative outcomes associated with their use.

The Effects of Text Messaging on Young Drivers

Hosking, S. G., Young, K. L., Regan, M. A. — Wed, 30 Sep 2009 09:52:04 PDT

Objective: This study investigated the effects of using a cell phone to retrieve and send text messages on the driving performance of young novice drivers. Background: Young drivers are particularly susceptible to driver distraction and have an increased risk of distraction-related crashes. Distractions from in-vehicle devices, particularly, those that require manual input, are known to cause decrements in driving performance. Method: Twenty young novice drivers used a cell phone to retrieve and send text messages while driving a simulator. Results: The amount of time that drivers spent not looking at the road when text messaging was up to ~400% greater than that recorded in baseline (no-text-messaging) conditions. Furthermore, drivers’ variability in lane position increased up to ~50%, and missed lane changes increased 140%. There was also an increase of up to ~150% in drivers’ variability in following distances to lead vehicles. Conclusion: Previous research has shown that the risk of crashing while dialing a handheld device, such as when text messaging and driving, is more than double that of conversing on a cell phone. The present study has identified the detrimental effects of text messaging on driving performance that may underlie such increased crash risk. Application: More effective road safety measures are needed to prevent and mitigate the adverse effects on driving performance of using cell phones to retrieve and send text messages.

The Interaction of Cognitive Load and Attention-Directing Cues in Driving

Lee, Y.-C., Lee, J. D., Ng Boyle, L. — Fri, 07 Aug 2009 13:56:25 PDT

Objective: This study investigated the effect of a nondriving cognitively loading task on the relationship between drivers’ endogenous and exogenous control of attention. Background: Previous studies have shown that cognitive load leads to a withdrawal of attention from the forward scene and a narrowed field of view, which impairs hazard detection. Method: Posner’s cue-target paradigm was modified to study how endogenous and exogenous cues interact with cognitive load to influence drivers’ attention in a complex dynamic situation. In a driving simulator, pedestrian crossing signs that predicted the spatial location of pedestrians acted as endogenous cues. To impose cognitive load on drivers, we had them perform an auditory task that simulated the demands of emerging in-vehicle technology. Irrelevant exogenous cues were added to half of the experimental drives by including scene clutter. Results: The validity of endogenous cues influenced how drivers scanned for pedestrian targets. Cognitive load delayed drivers’ responses, and scene clutter reduced drivers’ fixation durations to pedestrians. Cognitive load diminished the influence of exogenous cues to attract attention to irrelevant areas, and drivers were more affected by scene clutter when the endogenous cues were invalid. Conclusion: Cognitive load suppresses interference from irrelevant exogenous cues and delays endogenous orienting of attention in driving. Application: The complexity of everyday tasks, such as driving, is better captured experimentally in paradigms that represent the interactive nature of attention and processing load.

Trust and Reliance on an Automated Combat Identification System

Wang, L., Jamieson, G. A., Hollands, J. G. — Fri, 07 Aug 2009 13:56:25 PDT

Objective: We examined the effects of aid reliability and reliability disclosure on human trust in and reliance on a combat identification (CID) aid. We tested whether trust acts as a mediating factor between belief in and reliance on a CID aid. Background: Individual CID systems have been developed to reduce friendly fire incidents. However, these systems cannot positively identify a target that does not have a working transponder. Therefore, when the feedback is "unknown", the target could be hostile, neutral, or friendly. Soldiers have difficulty relying on this type of imperfect automation appropriately. Method: In manual and aided conditions, 24 participants completed a simulated CID task. The reliability of the aid varied within participants, half of whom were told the aid reliability level. We used the difference in response bias values across conditions to measure automation reliance. Results: Response bias varied more appropriately with the aid reliability level when it was disclosed than when not. Trust in aid feedback correlated with belief in aid reliability and reliance on aid feedback; however, belief was not correlated with reliance. Conclusion: To engender appropriate reliance on CID systems, users should be made aware of system reliability. Application: The findings can be applied to the design of information displays for individual CID systems and soldier training.

Interrater Reliability of Posture Observations

Bao, S., Howard, N., Spielholz, P., Silverstein, B., Polissar, N. — Fri, 07 Aug 2009 13:56:25 PDT

Objective: The aims of this research were (a) to study the interrater reliability of a posture observation method, (b) to test the impact of different posture categorization systems on interrater reliability, and (c) to provide guidelines for improving interrater reliability. Background: Estimation of posture through observation is challenging. Previous studies have shown varying degrees of validity and reliability, providing little information about conditions necessary to achieve acceptable reliability. Method: Seven raters estimated posture angles from video recordings. Different measures of interrater reliability, including percentage agreement, precision, expression as interrater standard deviation, and intraclass correlation coefficients (ICC), were computed. Results: Some posture parameters, such as the upper arm flexion and extension, had ICCs ≥ 0.50. Most posture parameters had a precision around the 10° range. The predefined categorization and 30° posture categorization strategies showed substantially better agreement among the raters than did the 10° strategy. Conclusions: Different interrater reliability measures described different aspects of agreement for the posture observation tool. The level of agreement differed substantially between the agreement measures used. Observation of large body parts generally resulted in better reliability. Wider width angle intervals resulted in better percentage agreement compared with narrower intervals. For most postures, 30°angle intervals are appropriate. Training aimed at using a properly designed data entry system, and clear posture definitions with relevant examples, including definitions of the neutral positions of the various body parts, will help improve interrater reliability. Application: The results provide ergonomics practitioners with information about the interrater reliability of a postural observation method and guidelines for improving interrater reliability for video-recorded field data.

Comparisons of Musculoskeletal Complaints and Data Entry Between a Sitting and a Sit-Stand Workstation Paradigm

Husemann, B., Von Mach, C. Y., Borsotto, D., Zepf, K. I., Scharnbacher, J. — Fri, 07 Aug 2009 13:56:25 PDT

Background: Seated working positions are often regarded as a cause for discomfort in the musculoskeletal system. Performing work in different working positions—that is, alternating between sitting and standing (sit-stand workstation paradigm)—could help reduce physical complaints. Objective: The questions were whether performing office work partly in a standing position leads to reduced complaints and whether standing would change the efficiency of data entry office work. Method: We investigated the effect of a sit-stand workstation paradigmd during experimental data entry office work on physical and psychological complaints and data entry efficiency by conducting a randomized controlled trial with 60 male participants ages 18 to 35 years. Results: In this experiment, musculoskeletal complaints were reduced by a sit-stand workstation paradigm. A trend could be identified indicating a small but nonsignificant loss of efficiency in data entry while standing. Conclusion: A sit-stand workstation paradigm reduces musculoskeletal complaints without considerably affecting data entry efficiency under the presented study conditions (young male participants, short duration, fixed and controlled sit-stand workstation paradigm, simulated experimental working condition). Application: According to the present data, implementing a sit-stand workstation paradigm can be an effective workplace health intervention to reduce musculoskeletal complaints. This experiment encourages further studies on the effectiveness of a sit-stand workstation paradigm. Experimental research and field studies that prove the reduction of complaints when introducing a sit-stand workstation paradigm in the workplace could be the basis for evidence-based recommendations regarding such interventions.

Cognitive Models of the Influence of Color Scale on Data Visualization Tasks

Breslow, L. A., Ratwani, R. M., Trafton, J. G. — Fri, 07 Aug 2009 13:56:25 PDT

Objective: Computational models of identification and relative comparison tasks performed on color-coded data visualizations were presented and evaluated against two experiments. In this context, the possibility of a dual-use color scale, useful for both tasks, was explored, and the use of the legend was a major focus. Background: Multicolored scales are superior to ordered brightness scales for identification tasks, such as determining the absolute numeric value of a represented item, whereas ordered brightness scales are superior for relative comparison tasks, such as determining which of two represented items has a greater value. Method: Computational models were constructed for these tasks, and their predictions were compared with the results of two experiments. Results: The models fit the experimental results well. A multicolored, brightness-ordered dual-use scale supported high accuracy on both tasks and fast responses on a comparison task but relatively slower responses on the identification task. Conclusion: Identification tasks are solved by a serial visual search of the legend, whose speed and accuracy are a function of the discriminability of the color scales. Comparison tasks with multicolored scales are performed by a parallel search of the legend; with brightness scales, comparison tasks are generally solved by a direct comparison between colors on the visualization, without reference to the legend. Finally, it is possible to provide users a dual-use color scale effective on both tasks. Application: Trade-offs that must typically be made in the design of color-coded visualizations between speed and accuracy or between identification and comparison tasks may be mitigated.

Uni- and Interdisciplinary Effects on Round and Handover Content in Intensive Care Units

Miller, A., Scheinkestel, C., Limpus, A., Joseph, M., Karnik, A., Venkatesh, B. — Fri, 07 Aug 2009 13:56:25 PDT

Objective: The aim of this study was to explore differences in the verbal content of handovers and rounds conducted in uni- and interdisciplinary social contexts. We expected higher proportions of goals to be articulated during interdisciplinary rounds. Background: Lack of explanatory connections between round improvement initiatives and outcomes suggest insufficient understanding about health care communications, especially the role of social interaction. Methods: The recognition-primed abstract decomposition space (RP-ADS) was used to analyze the information content of nurse handovers and morning rounds in a unidisciplinary- (physicians only) and an interdisciplinary-round intensive care unit (ICU). Data were collected using audio recordings of rounds and handovers for five patients for 5 days each in both ICUs. Results: Hierarchical log-linear analyses show strong associations between events (medical rounds vs. nurses’ shift handovers), type (uni- vs. interdisciplinary), and focus (levels of the RP-ADS) with highly significant combined two-way and higher-order interactions, LR²(df = 4) = 30.91, p < .0001. All tests of partial association were also highly significant. Differences among levels of the variables were evaluated using standardized residuals. Conclusion: Nurses focused on RP-ADS data and intervention levels, whereas physicians focused on diagnoses and expectations. Clinical goals that integrate these orientations emerged to a greater extent in interdisciplinary rounds. In addition, social context of rounds appears to influence nurse handovers. Unidisciplinary ICU nurse handovers consisted of a series of data-and intervention-related observations, whereas ICU nurse handovers in interdisciplinary ICUs tended to integrate data, interventions and clinical goals. Application: These results are relevant to the design and implementation of clinical communication improvement initiatives and support tools.

Coordination and Continuity of Intensive Care Unit Patient Care

Miller, A., Scheinkestel, C., Joseph, M. — Fri, 07 Aug 2009 13:56:26 PDT

Objective: Using Klein’s model of team coordination, we explored the null hypothesis that intensive care unit (ICU) care coordination unfolds as a linear sequence. Our intent was to generate hypotheses for further research and to provide interim recommendations for improving care coordination. We also explored factors contributing to care coordination (e.g., role responsibilities, support tools). Background: Although the body of clinical communications research is considerable, few studies address broader team processes in real-world environments; hence, these processes are not well understood. Methods: All bedside communications for 5 ICU patients were recorded for 5 days per patient and were coded using Klein’s model. Markov analysis was used to describe the care coordination process. Multivariate contingency table analysis and standardized parameter estimates described important contributing factors, and support tools were described using descriptive statistics. Results: First-, second-, and third-order Markov analyses show that care coordination does not unfold as a linear sequence; however, Markov diagrams suggest some process structure. Standardized parameter estimates of factors contributing to care coordination were calculated from a statistically significant three-way model (²[df = 18] = 36.95, p < .005). Role-based differences depend on context, with important differences in contributions to care coordination occurring within rounds. Tools supported only 48% of conversations. Conclusion: Three alternative research hypotheses were defined with at least a minimal level of support. Testing these hypotheses present substantial theoretical, methodological, and data analysis challenges. Application: Within a research framework, recommendations for change could achieve significant gains for understanding and for reducing breakdowns in care coordination.

Individual Differences in Route-Learning Strategy and Associated Working Memory Resources

Baldwin, C. L., Reagan, I. — Fri, 07 Aug 2009 13:56:26 PDT

Objective: The current investigation examined individual differences in route-learning strategies and their relative demands on visuospatial versus verbal working memory (WM) resources in virtual environments. Background: Learning new routes is a resource-demanding activity that must often be carried out in conjunction with other concurrent tasks. Virtual environments (VEs) are increasingly being used for training and research, pointing to the importance of determining the strategies people use to learn routes in these environments. Methods: Participants classified as having good or poor sense of direction (SOD) attempted to learn novel routes while concurrently performing either a verbal (articulatory suppression) or a visuospatial (tapping) WM interference task. Results: Different navigational strategies were observed in each SOD group. Individuals with poor SOD relied more heavily on verbal rather than visuospatial WM resources, as evidenced by greater disruption to route-learning performance from the articulatory suppression task relative to the tapping task. Conversely, individuals with good SOD exhibited more route-learning disruption from the tapping task, suggesting a greater reliance on visuospatial WM resources. Conclusion: Individuals differ from one another in the strategies they use and the WM resources they tap—verbal or visuospatial—to learn routes in VEs. Self-report measures can be used as indices of such individual differences in navigational strategy use in VE tasks. Application: Assessing SOD and associated WM resources have implications for targeted training for navigation in VEs and for the design of in-vehicle navigation systems.

Can Headway Reduction in Fog Be Explained by Impaired Perception of Relative Motion?

Caro, S., Cavallo, V., Marendaz, C., Boer, E. R., Vienne, F. — Fri, 07 Aug 2009 13:56:26 PDT

Objective: The goal of this study was to provide a better understanding of driver behavior in fog. Background: Impaired perception of changes in headway is hypothesized to be one of the reasons for shorter following distances in foggy conditions as compared with clear weather. Method: In the experiments described here, we measured response time for discriminating between whether the vehicle ahead is getting closer or farther away. Several visibility conditions were studied, ranging from a no-fog condition to a condition in which the vehicle could be seen only by its rear fog lights. Results: Fog conditions increased response times when the outline of the vehicle was barely visible or not visible at all. The longer response times in fog were attributable to the low contrast of the vehicle outline when still visible and to the smaller spacing between the two lights when the outline could not be properly perceived. Moreover, response times were found to be shorter for shorter following distances and for faster accelerations. Conclusion: Reducing headway could be a way for drivers to achieve faster discrimination of relative motion in foggy weather. More specifically, shortening one’s following distance until visibility of the lead vehicle changes from bad to good may have a perceptual control benefit, insofar as the response time gain compensates for the reduction in headway under these conditions. Applications: Potential applications include improving traffic safety. The results provide a possible explanation for close following in fog and point out the importance of rear-light design under these conditions.

Viewpoint Animation With a Dynamic Tether for Supporting Navigation in a Virtual Environment

Wang, W., Milgram, P. — Fri, 07 Aug 2009 13:56:26 PDT

Objective: This study examined the concept of dynamic viewpoint tethering for enhancing performance in 3-D avatar control tasks. Background: Dynamic viewpoint tethering refers to a viewpoint animation technique that couples a display viewpoint to a controlled avatar through a virtual tether. A dynamic tether, modeled as a mass spring damper system, can potentially generate desirable viewpoint behavior because of its ability to produce frequency-separated viewpoint responses. This study investigated the impact of a tether’s rigidity and damping properties on users’ navigational performance. Methods: Twelve participants took part in a simulated 3-D aerial navigational task. Performance was evaluated with respect to local guidance and global awareness. Results: Root mean square error scores revealed a decrease in local guidance performance when (a) the tether was either severely underdamped or overdamped and (b) the tether’s rigidity approached either zero or infinity. In addition, (c) global performance was better for higher-frequency forcing functions. Conclusion: Critical damping and medium rigidity can be optimized during design for enhancing users’ navigational efficiency. Application: Guidelines generated from this study support future viewpoint design in interactive virtual reality applications.

Cardiac Autonomic Control During Simulated Driving With a Concurrent Verbal Working Memory Task

Lenneman, J. K., Backs, R. W. — Fri, 07 Aug 2009 13:56:26 PDT

Objective: The objective of the study was to illustrate sensitivity and diagnosticity differences between cardiac measures and lane-keeping measures of driving performance. Background: Previous research suggests that physiological measures can be sensitive to the effects of driving and side task performance and diagnostic of the source of the attentional demands. We hypothesized that increases in side task difficulty would elicit physiological change without reduction of driving task performance and that the side task demands would elicit patterns of autonomic activity that map to specific attentional processing resources. Method: Separately and concurrently, thirty-two participants performed a simulated driving task and verbal working memory task (with two levels of difficulty, 0 back and 3 back) separately and concurrently. Attentional demands were assessed through physiological and performance measures. Results: Cardiac measures reflected changes in attentional demand from single- to dual-task driving with an n-back task, whereas lane-keeping measures did not. Furthermore, patterns of autonomic activity elicited by driving, n-back task, and dual-task driving with a 3-back task were consistent with our predictions about autonomic activity. Conclusion: Changes in cardiac measures without changes in lane-keeping measures provide evidence that cardiac measures can be sensitive to hidden costs in attention that do not manifest in coarse measures of driving performance. Furthermore, correct predictions regarding the patterns of autonomic activity elicited suggests that cardiac measures can serve as diagnostic tools for attention assessment. Application: Because of the demonstrated differences in sensitivity and diagnosticity, researchers should consider the use of cardiac measures in addition to driving performance measures when studying attention in a driving simulator environment.

Can Metric Feedback Training Hinder Actions Involving Distance?

Jones, K. S., DeLucia, P. R., Hall, A. R., Johnson, B. R. — Fri, 07 Aug 2009 13:56:26 PDT

Objective: The present studies tested whether distance estimation training with metric feedback can degrade the performance of untrained primarily perceptual-motor tasks. Background: Training with metric feedback can improve distance estimations. However, previous research led to the conclusion that those improvements stemmed from changes in cognitive processing rather than in perception. If trainees applied their new cognitive strategies to primarily perceptual-motor tasks, then the performance of those tasks should degrade. The present studies tested that possibility. Method: Experiment 1 sought to replicate that training with metric feedback would improve metric distance estimations. Experiments 2 and 3 investigated whether such training would degrade the performance of a primarily perceptual-motor task. Experiment 4 investigated whether such training would affect a perceptual-motor task that required cognition. Results: Metric feedback improved metric distance estimation (Experiments 1—4) and throwing to a specified distance (Experiment 4). Metric feedback degraded throwing to a target (Experiments 2 and 3), although that effect was not evident when pretesting was omitted (Experiment 3). Conclusion: If distance estimation trainees apply what they learned from metric feedback to untrained primarily perceptual-motor tasks, then the performance of those tasks will suffer. However, if trainees apply what they learned to untrained tasks that require metric estimation, then the performance of those tasks will improve. Application: Distance estimation training with metric feedback may not generalize to other tasks and may even degrade performance on certain tasks. Future research must specify the conditions under which distance estimation training with metric feedback leads to performance improvements and decrements.

How Accurate Is Information Transmitted to Medical Professionals Joining a Medical Emergency? A Simulator Study

Tue, 23 Jun 2009 10:26:56 PDT

Objective: This study used a high-fidelity simulation to examine factors influencing the accuracy of 201 pieces of information transmitted to nurses and physicians joining a medical emergency situation. Background: Inaccurate or incomplete information transmission has been identified as a major problem in medicine. However, only a few studies have assessed possible causes of transmission errors. Method: Each of 20 groups was composed of two or three nurses (first responders), one resident joining the group later, and one senior doctor joining last. Groups treated a patient suffering a cardiac arrest. Results: Multilevel binomial analyses showed that 18% of the information given to newcomers was inaccurate. Quantitative information requiring repeated updating was particularly error prone. Information generated earlier (i.e., older information) was more likely to be transmitted inaccurately. Explicitly encoding information to be transmitted after the physicians arrived at the scene enhanced accuracy, supporting transfer-appropriate processing theory. Conclusion: Information transmitted to nurses and physicians who join an ongoing emergency is only partly reliable. Therefore, medical professionals should not take accuracy for granted and should be aware of the nature of transmission errors. Application: Medical professionals should be trained in adequate encoding of information and in standardized communication procedures with regard to error-prone information. In addition, technical devices should be implemented that reduce reliance on memory regarding information with error-prone characteristics.

Using Informative Peripheral Visual and Tactile Cues to Support Task and Interruption Management

Hameed, S., Ferris, T., Jayaraman, S., Sarter, N. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: This study examined the effectiveness of using informative peripheral visual and tactile cues to support task switching and interruption management. Background: Effective support for the allocation of limited attentional resources is needed for operators who must cope with numerous competing task demands and frequent interruptions in data-rich, event-driven domains. One prerequisite for meeting this need is to provide information that allows them to make informed decisions about, and before, (re)orienting their attentional focus. Method: Thirty participants performed a continuous visual task. Occasionally, they were presented with a peripheral visual or tactile cue that indicated the need to attend to a separate visual task. The location, frequency, and duration parameters of these cues represented the domain, importance, and expected completion time, respectively, of the interrupting task. Results: The findings show that the informative cues were detected and interpreted reliably. Information about the importance (rather than duration) of the task was used by participants to decide whether to switch attention to the interruption, indicating adherence to experimenter instructions. Erroneous task-switching behavior (nonadherence to experimenter instructions) was mostly caused by misinterpretation of cues. Conclusion: The effectiveness of informative peripheral visual and tactile cues for supporting interruption management was validated in this study. However, the specific implementation of these cues requires further work and needs to be tailored to specific domain requirements. Application: The findings from this research can inform the design of more effective notification systems for a variety of complex event-driven domains, such as aviation, medicine, or process control.

Skill Acquisition While Operating In-Vehicle Information Systems: Interface Design Determines the Level of Safety-Relevant Distractions

Jahn, G., Krems, J. F., Gelau, C. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: This study tested whether the ease of learning to use human—machine interfaces of in-vehicle information systems (IVIS) can be assessed at standstill. Background: Assessing the attentional demand of IVIS should include an evaluation of ease of learning, because the use of IVIS at low skill levels may create safety-relevant distractions. Method: Skill acquisition in operating IVIS was quantified by fitting the power law of practice to training data sets collected in a driving study and at standstill. Participants practiced manual destination entry with two route guidance systems differing in cognitive demand. In Experiment 1, a sample of middle-aged participants was trained while steering routes of varying driving demands. In Experiment 2, another sample of middle-aged participants was trained at standstill. Results: In Experiment 1, display glance times were less affected by driving demands than by total task times and decreased at slightly higher speed-up rates (0.02 higher on average) than task times collected at standstill in Experiment 2. The system interface that minimized cognitive demand was operated more quickly and was easier to learn. Its system delays increased static task times, which still predicted 58% of variance in display glance times compared with even 76% for the second system. Conclusion: The ease of learning to use an IVIS interface and the decrease in attentional demand with training can be assessed at standstill. Application: Fitting the power law of practice to static task times yields parameters that predict display glance times while driving, which makes it possible to compare interfaces with regard to ease of learning.

The Effects of Insertion Method and Force on Hand Clearance Envelopes for Rubber Hose Insertion Tasks

Tue, 23 Jun 2009 10:26:56 PDT

Objective: The aim of this study was to determine how hand space for manual insertion of flexible hoses is affected by insertion method and force. Background: Adequate space is needed during assembly tasks in which workers join parts together with their hands. Hose installations are an example of such a task. Hand clearance envelopes for insertion tasks that involve cylindrical objects, such as a hose, are currently unavailable in the literature. Methods: Participants inserted a flexible 25-mm rubber hose onto a stationary flange using simulated methods similar to those observed in field studies of automotive assembly tasks. Markers placed on the back of the hand and wrists were used to measure postures during the insertion task. Results: Hand clearance envelopes for high-force insertions were significantly larger across methods by an average of 15% for both male (p < .05) and female (p < .01) participants. Rocking insertions resulted in the largest hand clearance envelopes compared with other insertion methods. Rocking and twisting the hose resulted in mean increases in the cross-sectional area of the hand clearance envelopes of 35% and 24%, respectively, compared with the straight push. Differences were significant (p < .05) for male and female participants for both bead height conditions. Conclusion: Both required insertion force and method affect hand clearance envelopes during simulated insertions. Application: These methods can be used by engineers to determine if there is adequate clearance for the hand to grip selected objects.

An Evidence Accumulation Model for Conflict Detection Performance in a Simulated Air Traffic Control Task

Neal, A., Kwantes, P. J. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: The aim of this article is to develop a formal model of conflict detection performance. Background: Our model assumes that participants iteratively sample evidence regarding the state of the world and accumulate it over time. A decision is made when the evidence reaches a threshold that changes over time in response to the increasing urgency of the task. Method: Two experiments were conducted to examine the effects of conflict geometry and timing on response proportions and response time. Results: The model is able to predict the observed pattern of response times, including a nonmonotonic relationship between distance at point of closest approach and response time, as well as effects of angle of approach and relative velocity. Conclusion: The results demonstrate that evidence accumulation models provide a good account of performance on a conflict detection task. Application: Evidence accumulation models are a form of dynamic signal detection theory, allowing for the analysis of response times as well as response proportions, and can be used for simulating human performance on dynamic decision tasks.

Do Familiar Teammates Request and Accept More Backup? Transactive Memory in Air Traffic Control

Smith-Jentsch, K. A., Kraiger, K., Cannon-Bowers, J. A., Salas, E. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: The present study investigated factors that explain when and why different groups of teammates are more likely to request and accept backup from one another when needed in an environment characterized by extreme time pressure and severe consequences of error: commercial air traffic control (ATC). Background: Transactive memory theory states that teammates develop consensus regarding the distribution of their relative expertise as well as confidence in that expertise over time and that this facilitates coordination processes. The present study investigated whether this theory could help to explain between-team differences in requesting and accepting backup when needed. Method: The present study used cross-sectional data collected from 51 commercial ATC teams. Hypotheses were tested using multiple regression analysis. Results: Teammates with greater experience working together requested and accepted backup from one another more than those with lesser experience working together. Teammate knowledge consensus and perceived team efficacy appear to have mediated this relationship. Conclusion: Transactive memory theory extends to high-stress environments in which members' expertise is highly overlapping. Teammates' shared mental models about one another increase the likelihood that they will request and accept backup. Application: Teammate familiarity should be considered when choosing among potential replacement team members. Training strategies that accelerate the development of teammate knowledge consensus and team efficacy are warranted.

Repeatability, Reproducibility, and Validity of a New Method for Characterizing Lumbar Support in Automotive Seating

Kolich, M. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: This article describes a new and more repeatable, reproducible, and valid test method for characterizing lumbar support in automotive seating. Background: Lumbar support is important because it affects occupant accommodation and perceptions of seat comfort. Assessing only the lumbar mechanism—particularly in terms of travel—is inadequate because it does not consider the effects of trim and foam. Method: The Society of Automotive Engineers' next-generation H-Point machine and associated loading protocol were used as the basis for the new test. Results: The method was found to satisfy minimum gage repeatability and reproducibility requirements. Validity was demonstrated through a regression model that revealed 93.9% of the variance in subjective ratings of poor uncomfortable lumbar support can be explained by two objective indicators: (1) lumbar support prominence in the full-off position and (2) effective travel. Conclusion: The method can be used to differentiate between seats offering two-way adjustable lumbar support. The best two-way adjustable lumbar seat systems are those that couple little to no lumbar support in the starting or off position (i.e., they are nonintrusive) with a considerable amount of effective or perceptible travel. Application: The automotive industry has long needed a way to address the fact that consumers want more lumbar support than their seats currently supply. This contribution offers a method to objectify an important aspect of automotive seating comfort—namely, lumbar support. This should help human factors professionals produce, but not necessarily guarantee, better consumer ratings.

Tactile Elevation Perception in Blind and Sighted Participants and Its Implications for Tactile Map Creation

Jehoel, S., Sowden, P. T., Ungar, S., Sterr, A. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: Our goal was to determine the optimal elevation of tactile map symbols. Background: Tactile perception research predicts that symbol elevation (vertical height) and texture on tactile maps could influence their readability. However, although research has shown that elevation influences detection and discrimination thresholds for single tactile stimuli and that the physiological response of fingertip receptors varies with texture, little is known about the influence of these parameters on the identification of stimuli in the context of multiple symbols as found on tactile maps. Method: Sighted and visually impaired participants performed tactile symbol identification tasks. In Experiment 1, we measured the effect of elevation on identification accuracy. In Experiment 2, we measured the effect of elevation and symbol texture on identification speed. Results: Symbol elevation influenced both speed and accuracy of identification; thresholds were higher than those found in work on detection and discrimination but lower than on existing tactile maps. Furthermore, as predicted from existing knowledge of tactile perception, rough features were identified more quickly than smooth ones. Finally, visually impaired participants performed better than sighted ones. Conclusion: The symbol elevations necessary for identification (0.040 to 0.080 mm) are considerably lower than would be expected on the basis of existing tactile maps (generally 0.5 mm or higher) and design guidelines (0.4 mm). Application: Tactile map production costs could be reduced and map durability increased by reducing symbol elevation. Furthermore, legibility of maps could be improved by using rough features, which are read more easily, and smaller symbols, which reduce crowding of graphics.

Simple Displays of Talker Location Improve Voice Identification Performance in Multitalker, Spatialized Audio Environments

Kilgore, R. M. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: The aim of this study was to assess the voice identification benefits of visual depictions of the relative locations of spatialized talkers in a serial listening task. Background: Although spatialized audio is known to improve speech intelligibility and voice identification accuracy within multitalker environments, prior studies have not found any additional benefit for augmenting spatialized audio with visual depictions of relative voice locations. These studies, however, were restricted to small audio environments (four voices), potentially limiting the ability of simple talker location displays to provide additional identification benefit. Method: In the first experiment, 18 participants performed a voice identification task for four- and eight-voice environments under three display conditions: (a) nonspatialized voices with an audio-only display, (b) spatialized voices with an audio-only display, and (c) spatialized voices augmented by a visual display of relative talker locations. In the second experiment, 32 participants performed the same voice identification task within a spatialized eight-voice environment but with audio and visual displays of differing angular scale. Results: Visually depicting relative talker locations improved voice identification performance in terms of both accuracy and response time, particularly for more populous auditory spaces. Both auditory and visual display scale affected these benefits, with large-angle displays performing the best for both modalities. Conclusion: Results indicate that simple visual representations of spatialized audio environments help listeners identify voices and that these representations are more effective when the angular spacing (auditory and visual) between talker locations is increased. Application: These results have important implications for the design and implementation of collaborative audio environments for shared, desktop, and portable communication devices.

Reference Frame Congruency in Search-and-Rescue Tasks

Pavlovic, N. J., Keillor, J., Hollands, J. G., Chignell, M. H. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: Our aim was to investigate how the congruency between visual displays and auditory cues affects performance on various spatial tasks. Background: Previous studies have demonstrated that spatial auditory cues, when combined with visual displays, can enhance performance and decrease workload. However, this facilitation was achieved only when auditory cues shared a common reference frame (RF) with the visual display. In complex and dynamic environments, such as airborne search and rescue (SAR), it is often difficult to ensure such congruency. Method: In a simulated SAR operation, participants performed three spatial tasks: target search, target localization, and target recall. The interface consisted of the camera view of the terrain from the aircraft-mounted sensor, a map of the area flown over, a joystick that controlled the sensor, and a mouse. Auditory cues were used to indicate target location. While flying in the scenario, participants searched for targets, identified their locations in one of two coordinate systems, and memorized their location relative to the terrain layout. Results: Congruent cues produced the fastest and most accurate performance. Performance advantages were observed even with incongruent cues relative to neutral cues, and egocentric cues were more effective than exocentric cues. Conclusion: Although the congruent cues are most effective, in cases in which the same cue is used across spatial tasks, egocentric cues are a better choice than exocentric cues. Application: Egocentric auditory cues should be used in display design for tasks that involve RF transformations, such as SAR, air traffic control, and unmanned aerial vehicle operations.

Using Computational Cognitive Modeling to Predict Dual-Task Performance With Sleep Deprivation

Gunzelmann, G., Byrne, M. D., Gluck, K. A., Moore, L. R. — Tue, 23 Jun 2009 10:26:56 PDT

Objective: The effects of fatigue on multiple-task performance were explored through computational cognitive modeling. Background: Fatigue typically has a negative impact on human performance. Biomathematical models exist that characterize the dynamics of human alertness, but the link between alertness and in situ performance on specific tasks is tenuous. Cognitive architectures offer a principled means of establishing that link. Method: We implemented mechanisms for fatigue, which produce microlapses in cognitive processing, into an existing model, adaptive control of thought—rational, and validated the performance predictions with Bratzke, Rolke, Ulrich, and Peters' data on fatigue and multiple-task performance. Results: The microlapse model replicated the human performance results very well with zero free parameters, although the fit was improved when we allowed two individual differences parameters to vary. Conclusion: Increased frequency of microlapses as a result of fatigue provides a parsimonious explanation for the impact of fatigue on dual-task performance and is consistent with previous research. Application: Our results illustrate how using biomathematical models of fatigue in conjunction with a cognitive architecture can result in accurate predictions of the effects of fatigue on dual-task performance. Extending and generalizing this capability has potential utility in any safety-critical domain in which fatigue may affect performance.

An Investigation of Driver Distraction Near the Tipping Point of Traffic Flow Stability

Tue, 23 Jun 2009 10:26:56 PDT

Objective: The purpose of this study was to explore the interrelationship between driver distraction and characteristics of driver behavior associated with reduced highway traffic efficiency. Background: Research on the three-phase traffic theory and on behavioral driving suggests that a number of characteristics associated with efficient traffic flow may be affected by driver distraction. Previous studies have been limited, however, by the fact that researchers typically do not allow participants to change lanes, nor do they account for the impact of varying traffic states on driving performance. Methods: Participants drove in three simulated environments with differing traffic congestion while both using and not using a cell phone. Instructed only to obey the speed limit, participants were allowed to vary driving behaviors, such as those involving forward following distance, speed, and lane-changing frequency. Results: Both driver distraction and traffic congestion were found to significantly affect lane change frequency, mean speed, and the likelihood of remaining behind a slower-moving lead vehicle. Conclusions: This research suggests that the behavioral profile of "cell phone drivers," which is often described as compensatory, may have far-reaching and unexpected consequences for traffic efficiency. Application: By considering the dynamic interplay between characteristics of traffic flow and driver behavior, this research may inform both public policy regarding in-vehicle cell phone use and future investigations of driving behavior.

Effects of Talker Sex and Voice Style of Verbal Cockpit Warnings on Performance

Arrabito, G. R. — Wed, 20 May 2009 10:36:00 PDT

Objective: The effects of talker sex and voice style of verbal cockpit warnings on performance were investigated to help make warning messages distinct from speech on the flight deck. Background: Auditory warnings are used in aircraft to alert the crew to hazards and their associated levels of danger. Failing to comply with a warning has led to aviation incidents and accidents. Methods: Participants were required to monitor the auditory channel and identify the verbal warning while simultaneously performing a visual pursuit tracking task. A male and a female actor annunciated the warning words in three styles: monotone, urgent, and whisper. In Experiment 1, warning words were presented in quiet, and in Experiment 2, they were presented in a background of speech babble that simulated cockpit radio communication. Results: Experiment 1 showed that the monotone and urgent styles resulted in the fastest identification response time (RT) regardless of the talker and listener's sex. Experiment 2 showed that the male talker annunciating in either the monotone or the urgent style resulted in the largest proportion correct and fastest identification RT regardless of the listener's sex. Both experiments showed effects of word semantics on performance. Conclusion: Effective use of speech parameters and word semantics can increase the saliency of verbal cockpit warnings. Application: Potential applications of this research include improving the attention-getting capability of an alerting system, which could lead to increased warning compliance, potentially resulting in fewer incidents and accidents.

Selection in Air Traffic Control: Is Nonradar Training a Predictor of Radar Performance?

Sethumadhavan, A., Durso, F. T. — Wed, 20 May 2009 10:36:00 PDT

Objective: The purpose of the current research was to investigate whether performance in nonradar training would predict performance in radar training. Background: There is a discussion in the Federal Aviation Administration about the necessity of keeping nonradar training as part of the required selection criteria for radar controllers. In nonradar training, controllers separate traffic by relying on the estimated time over navigational fixes printed on flight progress strips, rather than monitoring the perceptually available positional information on a radar screen. The two ways of controlling traffic—nonradar and radar—are different along a number of dimensions. Method: Sixteen participants were taught to control simulated air traffic using nonradar and radar procedures. Performance on final radar scenarios was predicted from cognitive variables; performance on earlier, simpler radar scenarios; and performance on nonradar scenarios. Results: Performance during nonradar trials predicted final radar performance (i.e., collisions and landed aircraft count) independent of the predictive power of cognitive variables and above and beyond earlier radar training. Conclusion: Performance in nonradar training enhanced users' ability to predict radar performance, even in addition to the predictive power of simpler, earlier radar performance variables. Good nonradar performers had higher situation awareness in the radar environment. Application: Performance in a nonradar environment may serve as an important selection tool in assessing the performance of student controllers in radar environments. The results indicate the need for future research with field controllers.

Analysis of Alternative Keyboards Using Learning Curves

Anderson, A. M., Mirka, G. A., Joines, S. M. B., Kaber, D. B. — Wed, 20 May 2009 10:36:00 PDT

Objective : To quantify learning percentages for alternative keyboards (chord, contoured split, Dvorak, and split fixed angle) and understand how physical, cognitive, and perceptual demand affect learning. Background: Alternative keyboards have been shown to offer ergonomic benefits over the conventional, single-plane QWERTY keyboard design, but productivity-related challenges may hinder their widespread acceptance. Method: Sixteen participants repeatedly typed a standard text passage using each alternative keyboard. Completion times were collected and subsequent learning percentages were calculated. Participants were asked to subjectively rate the physical, cognitive, and perceptual demands of each keyboard, and these values were then related to the calculated learning percentages. Results: Learning percentage calculations revealed the percentage for the split fixed-angle keyboard (90.4%) to be significantly different ( p < .05) from the learning percentages for the other three keyboards (chord, 77.3%; contour split, 76.9%; Dvorak, 79.1%). The average task completion time for the conventional QWERTY keyboard was 40 s, and the average times for the fifth trial on the chord, contoured split, Dvorak, and split fixed-angle keyboards were 346, 69, 181, and 42 s, respectively. Conclusions: Productivity decrements can be quickly regained for the split fixed-angle and contour split keyboard but will take considerably longer for Dvorak and chord keyboards. The split fixed-angle keyboard involved physical learning, whereas the others involved some combination of physical and cognitive learning, a result supported by the subjective responses. Application: Understanding the changes in task performance time that come with learning can provide additional information for a cost-benefit analysis when considering the implementation of ergonomic interventions.

Providing Training Enhances the Biomechanical Improvements of an Alternative Computer Mouse Design

Houwink, A., Oude Hengel, K. M., Odell, D., Dennerlein, J. T. — Wed, 20 May 2009 10:36:00 PDT

Objective: The purpose of this study is to determine if an alternative mouse promotes more neutral postures and decreases forearm muscle activity and if training enhances these biomechanical benefits. Background: Computer mouse use is a risk factor for developing musculoskeletal disorders; alternative mouse designs can help lower these risks. Ergonomic training combined with alternative input devices could be even more effective than alternative designs alone. Methods: Thirty healthy adults (15 males, 15 females) performed a set of computer mouse tasks with a standard mouse and an alternative mouse while an electromagnetic motion analysis system measured their wrist and forearm postures and surface electromyography measured the muscle activity of three wrist extensor muscles. Fifteen participants received no training on how to hold the alternative mouse, whereas the remaining 15 participants received verbal instructions before and during use of the alternative mouse. Results: The alternative mouse was found to promote a more neutral forearm posture compared with the standard mouse (up to 11.5° lower forearm pronation); however, pronation was further reduced when instructions on how to hold the mouse were provided. Wrist extensor muscle activity was reduced for the alternative mouse (up to 1.8% of maximum voluntary contraction lower) compared with the standard mouse, but only after participants received instructions. Conclusion: The alternative mouse design decreased biomechanical exposures; however, instructions enhanced this potential ergonomic benefit of the design. Application: User knowledge and training are important factors when effectively implementing an alternative ergonomic device.

Performance and Autonomic Responses During Motion Sickness

Dahlman, J., Sjors, A., Lindstrom, J., Ledin, T., Falkmer, T. — Wed, 20 May 2009 10:36:00 PDT

Objective: The aim of the study was to investigate how motion sickness, triggered by an optokinetic drum, affects short-term memory performance and to explore autonomic responses to perceived motion sickness. Background: Previous research has found that motion sickness decreases performance, but it is not known how short-term memory in particular is affected. Method: Thirty-eight healthy participants performed a listening span test while seated in a rotating optokinetic drum. Measurements of motion sickness, performance, heart rate, skin conductance, blood volume pulse, and pupil size were performed simultaneously throughout the experiment. Results: A total of 16 participants terminated the trial because of severe nausea, and the other 22 endured the full 25 min. Perceived motion sickness increased over time in both groups but less among those who endured the trial. Short-term memory performance decreased toward the end for those who terminated but increased in the other group. Results from the measured autonomic responses were ambiguous. Conclusion: We conclude that performance, measured as short-term memory, declines as perceived motion sickness progresses. Application: This research has potential implications for command and control personnel at risk of developing motion sickness.

Decision Making During Preoperative Surgical Planning

Wed, 20 May 2009 10:36:00 PDT

Objective: This study analyzes decision making during preoperative surgical planning through two cognitive indicators: conflict and cognitive control. Background: Planning is a critical stage in naturalistic decision making, and there is some evidence suggesting that this activity depends on the level of expertise and the demands of the task. The specificity of surgery resides in the necessity to cope with (potential) conflicts between the purpose of the surgical intervention and the biological laws governing the patient's body. Method: Six neurosurgeons (two board-certified neurosurgeons, two chief residents, and two residents) described the operative procedure envisaged on nine surgical cases of increasing surgical complexity. A detailed analysis of one surgical case described by one expert was performed. Moreover, we measured the number of conflicts and controls reported by each surgeon. Results: Two experts were the only ones for which the report of conflicts increased with surgical complexity (respectively, 75% and 73% of the conflict variance predicted by complexity). The two experts significantly activated a higher proportion of knowledge-based control (respectively, 43% and 38%) than did intermediates and residents. The residents significantly activated more motor skill—based controls (respectively, 40% and 44%) than did intermediates and experts. Conclusion: It seems that expert surgical decision making to cope with task demands is significantly associated with conflict monitoring. Knowledge-based control to regulate conflict is mainly produced by experts. Application: Conflicts and controls analyzed through verbal reports can be used as relevant indicators to highlight critical moments in decision making that potentially require assistance from information systems.

Modulation-Based Digital Noise Reduction for Application to Hearing Protectors to Reduce Noise and Maintain Intelligibility

Chung, K., Tufts, J., Nelson, L. — Wed, 20 May 2009 10:36:00 PDT

Objective: The objective of this study was to test the effects of modulation-based digital noise reduction (MB-DNR) on noise levels, speech intelligibility, and listening preference in four real-world noises. Background: A significant challenge in hearing protection device (HPD) design is to reduce ambient noise levels while maintaining users' ability to understand speech. MB-DNR technology, currently employed in hearing aids, potentially could be used to achieve these objectives. Methods: Speech and noise calibrated to signal-to-noise ratios (SNRs) of 0, —5, and —10 dB in the sound field were recorded at the outputs of two digital hearing aids in the ears of a Knowles Electronic Manikin for Acoustic Research with and without MB-DNR activated (i.e., NR and noNR, respectively). Listeners' speech intelligibility scores and sound quality preferences were evaluated while they listened to the recordings presented via ER-3A insert earphones at 85 dB SPL. Results: MB-DNR reduced the overall noise level by approximately 4 to 7 dB. Listeners obtained significantly higher speech intelligibility scores in the NR condition at an SNR of —10 dB in two noises and similar scores in the noNR and NR conditions in all other cases. They preferred the NR condition in all cases. Conclusion: MB-DNR reduced overall noise level, enhanced sound quality, and maintained or improved speech intelligibility in the four military noises tested. Applications: MB-DNR algorithms potentially could be incorporated into HPDs to enhance performance and increase user acceptance.

A Model of Clutter for Complex, Multivariate Geospatial Displays

Lohrenz, M. C., Trafton, J. G., Beck, M. R., Gendron, M. L. — Wed, 20 May 2009 10:36:00 PDT

Objective: A novel model of measuring clutter in complex geospatial displays was compared with human ratings of subjective clutter as a measure of convergent validity. The new model is called the color-clustering clutter (C3) model. Background: Clutter is a known problem in displays of complex data and has been shown to affect target search performance. Previous clutter models are discussed and compared with the C3 model. Method: Two experiments were performed. In Experiment 1, participants performed subjective clutter ratings on six classes of information visualizations. Empirical results were used to set two free parameters in the model. In Experiment 2, participants performed subjective clutter ratings on aeronautical charts. Both experiments compared and correlated empirical data to model predictions. Results: The first experiment resulted in a .76 correlation between ratings and C3. The second experiment resulted in a .86 correlation, significantly better than results from a model developed by Rosenholtz et al. Outliers to our correlation suggest further improvements to C3. Conclusions: We suggest that (a) the C3 model is a good predictor of subjective impressions of clutter in geospatial displays, (b) geospatial clutter is a function of color density and saliency (primary C3 components), and (c) pattern analysis techniques could further improve C3. Application: The C3 model could be used to improve the design of electronic geospatial displays by suggesting when a display will be too cluttered for its intended audience.

Driver Reaction Time to Tactile and Auditory Rear-End Collision Warnings While Talking on a Cell Phone

Mohebbi, R., Gray, R., Tan, H. Z. — Wed, 20 May 2009 10:36:00 PDT

Objective: This study examined the effectiveness of rear-end collision warnings presented in different sensory modalities while drivers were engaged in cell phone conversations in a driving simulator. Background: Tactile and auditory collision warnings have been shown to improve braking response time (RT) in rear-end collision situations. However, it is not clear how effective these warnings are when the driver is engaged in attentionally demanding secondary tasks, such as talking on a cell phone. Method: Sixteen participants in a driving simulator experienced three collision warning conditions (none, tactile, and auditory) in three conversation conditions (none, simple hands free, complex hands free). Driver RT was captured from warning onset to brake initiation (WON2B). Results: WON2B times for auditory warnings were significantly larger for simple conversations compared with no conversation (+148 ms), whereas there was no significant difference between these conditions for tactile warnings (+53 ms). For complex conversations, WON2B times for both tactile (+146 ms) and auditory warnings (+221 ms) were significantly larger than during no conversation. During complex conversations, tactile warnings produced significantly shorter WON2B times than no warning (—141 ms). Conclusion: Tactile warnings are more effective than auditory warnings during both simple and complex conversations. Application: These results indicate that tactile rear-end collision warnings have the potential to offset some of the driving impairments caused by cell phone conversations.