Optimal solutions for complex design problems: Using isoperformance software for human factors trade offs

A major application of isoperformance is as a trade-off methodology of the three major drivers of system design; equipment, training variables, and user characteristics. The flexibility of isoperformance allows each of these three components to be nearly any rational variation. For example, aptitude may be military Armed Forces Qualification Testing (AFQT) categories, cutoff scores within a selection procedure, or simply dichotomizing high and low scorers (pass/fail). Equipment may be new versus old, 'smart' versus dumb, high versus low resolution, etc. Training may be short versus long or varieties of media types (lecture versus CAI/CBI versus self-paced workbooks). In its final computerized form isoperformance lets the user set an operational level of performance (e.g., a jet pilot in a simulated emergency must take prescribed corrective action and clear the plane in several seconds, pilot astronauts will check out all shuttle flight systems within 30 minutes, or Mission Specialists must handle sucdessfully a required number of job elements). At this point the computer program guides the user through any requested trade-offs of the three components while maintaining the specified operational level of performance through isoperformance curves. A demonstration of the computer program is currently available

A menu of self-administered microcomputer-based neurotoxicology tests

This study examined the feasibility of repeated self-administration of a newly developed battery of mental acuity tests. Researchers developed this battery to be used to screen the fitness for duty of persons in at-risk occupations (astronauts, race car drivers), or those who may be exposed to environmental stress, toxic agents, or disease. The menu under study contained cognitive and motor tests implemented on a portable microcomputer including: a five-test core battery, lasting six minutes, which had demonstrable reliabilities and stability from several previous repeated-measures studies, and also 13 new tests, lasting 42 minutes, which had appeared in other batteries but had not yet been evaluated for repeated-measures implementation in this medium. Sixteen subjects self-administered the battery over 10 repeated sessions. The hardware performed well throughout the study and the tests appeared to be easily self-administered. Stabilities and reliabilities of the test from the core battery were comparable to those obtained previously under more controlled experimental conditions. Analyses of metric properties of the remaining 13 tests produced eight additional tests with satisfactory properties. Although the average retest reliability was high, cross-correlations between tests were low, indicating factorial richness. The menu can be used to form batteries of flexible total testing time which are likely to tap different mental processes and functions

Development of microcomputer-based mental acuity tests for repeated-measures studies

The purpose of this report is to detail the development of the Automated Performance Test System (APTS), a computer battery of mental acuity tests that can be used to assess human performance in the presence of toxic elements and environmental stressors. There were four objectives in the development of APTS. First, the technical requirements for developing APTS followed the tenets of the classical theory of mental tests which requires that tests meet set criteria like stability and reliability (the lack of which constitutes insensitivity). To be employed in the study of the exotic conditions of protracted space flight, a battery with multiple parallel forms is required. The second criteria was for the battery to have factorial multidimensionality and the third was for the battery to be sensitive to factors known to compromise performance. A fourth objective was for the tests to converge on the abilities entailed in mission specialist tasks. A series of studies is reported in which candidate APTS tests were subjected to an examination of their psychometric properties for repeated-measures testing. From this work, tests were selected that possessed the requisite metric properties of stability, reliability, and factor richness. In addition, studies are reported which demonstrate the predictive validity of the tests to holistic measures of intelligence

Microcomputer-based tests for repeated-measures: Metric properties and predictive validities

A menu of psychomotor and mental acuity tests were refined. Field applications of such a battery are, for example, a study of the effects of toxic agents or exotic environments on performance readiness, or the determination of fitness for duty. The key requirement of these tasks is that they be suitable for repeated-measures applications, and so questions of stability and reliability are a continuing, central focus of this work. After the initial (practice) session, seven replications of 14 microcomputer-based performance tests (32 measures) were completed by 37 subjects. Each test in the battery had previously been shown to stabilize in less than five 90-second administrations and to possess retest reliabilities greater than r = 0.707 for three minutes of testing. However, all the tests had never been administered together as a battery and they had never been self-administered. In order to provide predictive validity for intelligence measurement, the Wechsler Adult Intelligence Scale-Revised and the Wonderlic Personnel Test were obtained on the same subjects

The Gut Microbiota of Helix aspersa

The Gut Microbiota of Helix aspersa. The gut microbiota plays an important role in the host organism’s well-being, contributing to the host’s immunity and metabolism. An individual’s total gut microbiota is dynamic, fluctuating in response to changes in diet and environmental stressors; however, a host often has a subset of gut microorganisms, known as the core gut microbiome, which is consistent among individuals in a population. To study the gut microbiota, we are using the common garden snail, Helix aspersa, as our model organism. In the past, culture-based studies have been used to identify bacteria from the gut of Helix aspersa raised on processed food sources, which can alter the gut microbiota. Little has been done using metagenomics to determine the natural gut microbiota or identify a core microbiome. We analyzed 16S bacterial diversity in the feces of wild-caught snails using high-throughput Illumina sequencing of the V1 and V2 variable regions. Our results show a gut microbiota dominated by Gammaproteobacteria, particularly members of genus Buttiauxella. This finding was notable in that several early culture-based studies identified this genus as snail specific. More recent DNA-based work has identified this genus at low levels in soil and water environments. Given these data, we assessed the microbial community present on the snail food source, confirming low levels of Buttiauxella and high levels of Pseudomonas. This finding suggests that Helix selectively uptake microbes from their food-source and/or avoid potentially harmful Pseudomonas. We are using FISH microscopy and plating techniques to study changes in the gut microbiota of individual snails in response to changes in their feeding regimen, and exposure to antibiotics or bacterial stressors

Aftereffects from Virtual Environment Exposure: How Long do They Last?

The duration of the aftereffects from virtual environment (VE) exposure are not well characterized to date. Yet information concerning the incidence and enduring nature of these effects is essential to delimit the effective and safe use of VE technology. This study examined the aftereffects from VE exposure after three different exposure periods ranging from 15 to 45 minutes. Sixty participants were randomly assigned to one of the exposure periods, twenty to each condition. Sickness symptomatology, eye-hand coordination, and postural stability were measured before and after exposure. There were five measurements taken after exposure at 15 minute intervals. The results from the sickness symptomatology have been analyzed to date and show significantly higher symptomatology that persists for the entire post-exposure period in which measurements were taken. One hour after exposure the Total Severity of symptoms were 12 times higher than pre-exposure levels. Examining the three sub-dimensions of these symptoms indicated that one hour after exposure Nausea symptoms were 10x\u27s higher, Oculomotor disturbances were 7x\u27s higher and Disorientation was 95x\u27s higher than pre-exposure levels. The very high levels of reported Disorientation are consistent with other studies that indicate that VE systems engender high levels of dizziness and vertigo upon post-exposure. The tangible and persistent aftereffects raise concerns for the safety and well being of VE system users and suggest that their activities should be monitored upon post exposure

Locus of User-Initiated Control in Virtual Environments: Influences on Cybersickness

Cybersickness is a pervasive and deletenous effect of human-virtual environment interaction. This paper applies motion-sickness adaptation theory to cybersickness in virtual environments to determine if the degree of user-initiated control can suppress sickness. It is suggested that if users are allowed some level of control over their movement within a virtual environment, cybersickness will not be as severe as that resulting from an enviornment in which users must follow a predetermined (i.e., scripted) path of movement. While past motion-sickness studies have examined control versus no control, the present study focuses on modifying the level of user-initiated control such that it matches the needs of the task characteristics while minimizing sickness. The degree of user sickness was tested under passive, active, and active-passive control scenarios. As measured by the Simulator Sickness Questionnaire, the active (i.e., complete control) condition reduced the severity of the symptoms experienced as compared to the passive (i.e., no control) condition, but did not do so as completely as the active-passive (i.e., coupled control) condition. The implication is that the level of user-initiated control can be manipulated to modify the deleterious effects of human-virtual environment interaction