Robert E. Schlegel

Coefficient of Friction and Subjective Assessment of Slippery Work Surfaces

Research was conducted to determine how well subjects could distinguish between surfaces with different coefficient of friction (COF) values and to evaluate how well subjective ratings of slipperiness correlated with the actual COF values. Thirty-three ironworkers experienced in working and walking on steel surfaces and 23 university students inexperienced with these tasks participated in the study. Subjective slipperiness ratings for a variety of climbing and walking conditions were obtained from the subjects. It was found that subjects could identify differences in the slipperiness of four types of steel coatings tested in the study. There was a high correlation between the subjective ratings and the measured COF values. Subjects did not slip at a COF of 0.41 but did lose footing at a COF of 0.20.

Tactile stimulation of the human head for information display

A series of three studies was conducted to explore the use of tactile stimulation or light tapping of the human head to inform a pilot of possible threats or other situations in the flight environment. Study I confirmed that subjects could achieve 100% detection of the tactile stimuli. Localization performance, measured in Study 2, depended on the number of different stimulus sites and ranged from 93% accuracy for 6 sites to 47% accuracy for 12 sites across the parietal meridian of the head. In Study 3 we investigated the effect of performing the localization task simultaneously with a dual memory/tracking task or an air combat simulation task. These studies demonstrated that tactile information display could be an integral contributor to improved situation awareness, but not without cost to other task performance. The results of Study 3 were also examined with reference to popular models of attention and workload.

Cognitive performance aboard the life and microgravity spacelab.

The impact of microgravity and other stressors on cognitive performance need to be quantified before long duration space flights are planned or attempted since countermeasures may be required. Four astronauts completed 38 sessions of a 20-minute battery of six cognitive performance tests on a laptop computer. Twenty-four sessions were preflight, 9 sessions were in-orbit, and 5 sessions were postflight. Mathematical models of learning were fit to each subjects preflight data for each of 14 dependent variables. Assuming continued improvement, expected values were generated from the models for in-orbit comparison. Using single subject designs, two subjects showed statistically significant in-orbit effects. One subject was degraded in two tests, the other was degraded in one test and exceeded performance expectations in another. Other subjects showed no statistically significant effects on the tests. The factors causing the deterioration in the two subjects can not be determined without appropriate ground-based control groups.

Automated neuropsychological assessment metrics (v4) traumatic brain injury battery: military normative data

The aim of the present study was to establish normative data for the Automated Neuropsychological Assessment Metrics (v4) Traumatic Brain Injury (ANAM4 TBI) battery in a military context. ANAM4 data from over 107,500 active duty service members ranging from 17 to 65 years of age were included in this study. The influence of the demographic variables of age and gender were also examined. These norms, stratified by age and gender, represent a more comprehensive set of norms than previously available and are provided as a representative set of norms for clinical practice. Additionally, base rates of below average performance in a normal population are provided to help inform clinical decision making.

Spectral analysis in quality control: a control chart based on the periodogram

Variations in manufacturing processes are expected to fluctuate around a constant level called the process mean. This article is concerned with the development of a control chart that detects cycles in the process mean. The new control chart, the spectral control chart, is based on the periodogram. The value plotted at each point in time is the ratio of the largest periodogram ordinate to the average of all ordinates. When an observation falls above the prescribed control limit, an out-of-control signal is given. The spectral control chart is compared with the Shewhart and geometric moving average charts. Data obtained from Monte Carlo simulations show that the spectral control chart is superior for detecting cyclic variations but that it is not effective for detecting shifts in the process mean. Thus the spectral control chart should be used along with existing control charts so that both shifts and cycles in the process mean can be detected.

The NASA performance assessment workstation: Cognitive performance during head-down bed rest

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 degrees head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.

An investigation of heat stress effects on time-sharing performance

A study was conducted to investigate the effects of heat stress on time-sharing performance. Twelve participants performed three dual-task scenarios and a multiple-task scenario for 2 h in each of six climates. The climates were obtained by generating each of three wet bulb globe temperatures (WBGT; 22, 28 and 34°C) with two relative humidity levels (30 and 70%). The dual tasks selected from the Criterion Task Set (CTS) were: (1) display monitoring with mathematical processing; (2) memory search with mathematical processing; and (3) unstable tracking with memory search. The multiple task scenario was generated using the SYNTASK software. The results indicated a significant heat stress effect on CTS display monitoring and unstable tracking performance and on the SYNTASK visual monitoring and auditory discrimination tasks. Additionally, at 34°C WBGT, 70% relative humidity was more detrimental to performance than 30% relative humidity. Results were interpreted using the Maximal Adaptability Model and Shingledeckers information processing stage/resource framework. To describe the results in an orderly manner, the authors propose the concept of heat stress selectivity effects. In addition, the results were used to evaluate whether the most recent NIOSH recommended heat stress standard, which is based solely on physiological and medical criteria, protects time-sharing performance. It was concluded that the NIOSH criterion does offer protection up to 28°C WBGT.

Evidence for Added Value of Baseline Testing in Computer-Based Cognitive Assessment

CONTEXT Large-scale baseline cognitive assessment for individuals at risk for concussion is a common part of the protocol for concussion-surveillance programs, particularly in sports. Baseline cognitive testing is also being conducted in US military service members before deployment. Recently, the incremental validity of large-scale baseline cognitive assessment has been questioned. OBJECTIVE To examine the added value of baseline cognitive testing in computer-based neuropsychological assessment by comparing 2 methods of classifying atypical performance in a presumed healthy sample. DESIGN Cross-sectional study. SETTING Military base. PATIENTS OR OTHER PARTICIPANTS Military service members who took the Automated Neuropsychological Assessment Matrix (ANAM) before and after deployment (n = 8002). MAIN OUTCOME MEASURE(S) Rates of atypical performance in this healthy, active-duty sample were determined first by comparing postdeployment scores with a military normative database and then with each individuals personal baseline performance using a reliable change index. RESULTS Overall rates of atypical performance were comparable across these 2 methods. However, these methods were highly discordant in terms of which individuals were classified as atypical. When norm-referenced methods were used, 2.6% of individuals classified as normal actually demonstrated declines from baseline. Further, 65.7% of individuals classified as atypical using norm-referenced scores showed no change from baseline (ie, potential false-positive findings). CONCLUSIONS Knowing an individuals baseline performance is important for minimizing potential false-positive errors and reducing the risks and stresses of misdiagnosis.

An observational technique for physical work stress analysis

This paper describes an observational method of physical work stress analysis which has the ease of application of traditional work study techniques but with greater account of human and task variables. The technique involves the process of activity sampling of various physical components of work, including body location, support base, orientation, hand position, acceleration and thermal load. Component weighting is achieved by expert judgement, and the results of investigations indicate good correlations with both subjective and physiological predictors of physical work stress. A final facility of this method is the adoption of a novel polar graph display medium in which the sector angles represent the component weights and the radii represent the measured values. Thus, the physical work stress profile is represented both by area and shape characteristics of the display to indicate the instantaneous load and static / dynamic load balance.

Effects of Military Deployment on Cognitive Functioning

Military deployment poses many risks for cognitive functioning. When deployed individuals are compared to a nondeployed control group, there is some evidence that deployment may be associated with declines in cognitive functioning. The current study examined cognitive performance before and following deployment in a large sample of active duty military personnel (N = 8002) who reported no traumatic brain injury (TBI). Cognition was assessed using the Automated Neuropsychological Assessment Metrics version 4 TBI Military (ANAM4 TBI-MIL) battery, a computer-based battery of tests measuring attention, processing speed, and general cognitive efficiency. Pre- and postdeployment scores were compared using repeated measures analyses. Although statistically significant differences were observed for all tests (with 5 of 7 tests demonstrating performance improvement), effect sizes were very small for all but 1 test, indicating that performance differences had minimal clinical significance. Likewise, determination of change for individuals using reliable change indices revealed that a very small percentage (<3%) of this presumed healthy sample showed meaningful decline in cognition following deployment. Analyses indicated that despite risks for cognitive decline while in theater, deployment had minimal to no lasting effect on cognition as measured by ANAM4 TBI-Mil upon return from deployment.