Human Factors: The Journal of the Human Factors and Ergonomics Society RSS feed -- OnlineFirst Articles

Psychophysiological Responses in Women During Cart Pushing on Different Frictional Walkways

Maikala, R. V., Ciriello, V. M., Dempsey, P. G., O'Brien, N. V. — Thu, 19 Nov 2009 12:38:09 PST

Objective: The aim of this study was to evaluate psychophysically determined acceptable forces, cardiopulmonary, and calf muscle metabolic responses in 15 workers while they pushed an instrumented cart on two walkways. Background: In addition to the potential for increased musculoskeletal disorders in workers, pushing on various terrains is associated with occurrence of slips and falls at the workplace. Method: Using a psychophysical approach, participants chose the maximum acceptable cart weight they could push without strain on walkways with coefficient of friction equaling 0.68 (plywood) and 0.26 (Teflon-coated.). Then, while participants pushed their psychophysically chosen cart weight for 2 hr on each walkway, horizontal and vertical forces applied on the cart handle and physiological responses were collected. Cardiopulmonary responses were measured using a telemetric metabolic cart. A tissue hemoglobin index (THI) and a tissue oxygenation index (TOI) from the right and left calf muscles were obtained using near-infrared spectroscopy. Results: Participants generated higher horizontal forces (by 26%) on plywood than that on Teflon. Cardiopulmonary and TOI and THI responses were similar between walkways. However, greater ratios of absolute oxygen uptake per force (by 19%) and TOI per force (by 24%) on Teflon were demonstrated in the horizontal direction than on plywood. Conclusions: This increased muscle oxygenation–force ratio, coupled with increased oxygen uptake per force generated on Teflon, might suggest that pushing on the slippery surface results in higher metabolic demand. Application: Findings from the present study will assist in revising previously established acceptable forces and in relating these forces to physiological responses with respect to pushing on different frictional walkways.

Isolating the Effects of Vection and Optokinetic Nystagmus on Optokinetic Rotation-Induced Motion Sickness

Ji, J. T. T., So, R. H. Y., Cheung, R. T. F. — Tue, 17 Nov 2009 11:41:55 PST

Objective: This study investigates isolated effects of vection and optokinetic nystagmus (OKN) on visually induced motion sickness (VIMS) provoked by rotating optokinetic drum patterns. Background: VIMS was the subject of recent standardization activities, but the effects of OKN have not been studied in the absence of vection. Method: Experiment 1 suppressed OKN by eye fixation and examined VIMS severity (both ordinal and ratio scale) and time spent in saturated vection at four pattern rotating velocities of 0, 2, 14, and 34 degrees per second (dps). Experiment 2 suppressed vection by adding a peripheral visual field rotating in the opposite direction to the rotating patterns. VIMS severity and OKN slow-phase velocity were studied at four rotating velocities of 0, 30, 60, and 90 dps. Results: Results from Experiment 1 indicated that VIMS severity increased as the pattern velocity increased from 0 dps to 34 dps. Results from Experiment 2 indicated that as the velocity of the rotating pattern increased, the slow-phase velocity of OKN and the severity of VIMS increased and peaked in the 60-dps condition. In both experiments, ratio-scaled nausea data significantly correlated with ordinal-scaled nausea ratings. Conclusion: VIMS can still occur in the absence of either vection or OKN. Interestingly, the profile of the summed results of the two experiments matches nicely with the profile reported by Hu et al. in which neither OKN nor vection were controlled. Application: Potential applications include modeling and reduction of VIMS in computer gaming environments.

Identifying Black Swans in NextGen: Predicting Human Performance in Off-Nominal Conditions

Wickens, C. D., Hooey, B. L., Gore, B. F., Sebok, A., Koenicke, C. S. — Tue, 17 Nov 2009 11:41:55 PST

Objective: The objective is to validate a computational model of visual attention against empirical data—derived from a meta-analysis—of pilots’ failure to notice safety-critical unexpected events. Background: Many aircraft accidents have resulted, in part, because of failure to notice nonsalient unexpected events outside of foveal vision, illustrating the phenomenon of change blindness. A model of visual noticing, N-SEEV (noticing– salience, expectancy, effort, and value), was developed to predict these failures. Method: First, 25 studies that reported objective data on miss rate for unexpected events in high-fidelity cockpit simulations were identified, and their miss rate data pooled across five variables (phase of flight, event expectancy, event location, presence of a head-up display, and presence of a highway-in-the-sky display). Second, the parameters of the N-SEEV model were tailored to mimic these dichotomies. Results: The N-SEEV model output predicted variance in the obtained miss rate (r = .73). The individual miss rates of all six dichotomous conditions were predicted within 14%, and four of these were predicted within 7%. Conclusion: The N-SEEV model, developed on the basis of an independent data set, was able to successfully predict variance in this safety-critical measure of pilot response to abnormal circumstances, as collected from the literature. Applications: As new technology and procedures are envisioned for the future airspace, it is important to predict if these may compromise safety in terms of pilots’ failing to notice unexpected events. Computational models such as N-SEEV support cost-effective means of making such predictions.

Auditory Decision Aiding in Supervisory Control of Multiple Unmanned Aerial Vehicles

Donmez, B., Cummings, M.L., Graham, H. D. — Tue, 17 Nov 2009 11:41:56 PST

Objective: This article is an investigation of the effectiveness of sonifications, which are continuous auditory alerts mapped to the state of a monitored task, in supporting unmanned aerial vehicle (UAV) supervisory control. Background: UAV supervisory control requires monitoring a UAV across multiple tasks (e.g., course maintenance) via a predominantly visual display, which currently is supported with discrete auditory alerts. Sonification has been shown to enhance monitoring performance in domains such as anesthesiology by allowing an operator to immediately determine an entity’s (e.g., patient) current and projected states, and is a promising alternative to discrete alerts in UAV control. However, minimal research compares sonification to discrete alerts, and no research assesses the effectiveness of sonification for monitoring multiple entities (e.g., multiple UAVs). Method: The authors conducted an experiment with 39 military personnel, using a simulated setup. Participants controlled single and multiple UAVs and received sonifications or discrete alerts based on UAV course deviations and late target arrivals. Results: Regardless of the number of UAVs supervised, the course deviation sonification resulted in reactions to course deviations that were 1.9 s faster, a 19% enhancement, compared with discrete alerts. However, course deviation sonifications interfered with the effectiveness of discrete late arrival alerts in general and with operator responses to late arrivals when supervising multiple vehicles. Conclusions: Sonifications can outperform discrete alerts when designed to aid operators to predict future states of monitored tasks. However, sonifications may mask other auditory alerts and interfere with other monitoring tasks that require divided attention. Applications: This research has implications for supervisory control display design.