Ergonomics
-
In this study, a physiological model to explain the pathway of CO2 output during incremental exercise was examined by referring to experimental data. Since CO2 output (VCO2) shows multiple correlations with mixed venous CO2 pressure (PvCO2) and arterial CO2 pressure (PaCO2), the increase in the difference between PvCO2 and PaCO2 was considered to be involved in the increase in VCO2. In order to better understand the influence of CO2 pressure, VCO2 was divided into the expiratory CO2 phase (non-lactic VCO2), which was unrelated to lactic acid increase and the expiratory CO2 phase (excess VCO2), which was related to lactic acid increase. ⋯ The CO2 excess, which was obtained by adding excess VCO2 in terms of the lapse of exercise time, correlated significantly with an increase in lactate in the blood. Based on the results, a model was constructed to illustrate the pathway of CO2 output. The key points of the model were as follows: (1) the use of the blood CO2 dissociation curve as the vector to transport CO2 from tissue to lungs, (2) the standard value of PaCO2 was established in order to divide non-lactic VCO2 and excess VCO2, (3) the dextroversion of the blood CO2 dissociation curve due to lactic acid was connected to excess VCO2, and (4) a decrease in PaCO2 was related to excess VCO2 derived from tissue.
-
The purpose of the present study was to analyse the effects of information complexity on Pilot Mental WorkLoad (PMWL) and Pilot Performance (PP), and to analyse the structure of PMWL. Eighteen pilots performed 72 simulated low level-high speed emissions. The complexity of the Head Down Display (HDD) information varied as a function of the tactical situation. ⋯ Heart rate (sortie means) correlated positively with PMWL (r = 0.34, p <0.05) and perceived complexity of mission (r = 0.37, p < 0.01). Heart rate (running means) covaried with variations in information complexity for those pilots who performed well. From spectral analyses of cardiac interval times it was found that the amplitude of the 0.10 Hz component tended to decrease during high as compared to low levels of information load.
-
This study reports a detailed investigation of the interaction between goal setting, anxiety and perceptuo-motor performance. Forty-four subjects completed familiarization, control and treatment conditions in which they were required to perform a series of perceptual speed trials. In the control condition, subjects were assigned a vague, general goal of 'do your best', whilst in the treatment condition, increasingly difficult, specific goals were assigned. ⋯ In the treatment condition, an increase in cognitive anxiety and a reduction in self-confidence accompanied increasing goal difficulty but these remained stable in the control condition. Performance was greater when 'do your best' as opposed to 'very easy' goals were assigned, but this situation was reversed when 'very hard' goals were assigned. The results of these laboratory-based findings are discussed with particular reference to the implications for practitioners in applied settings.
-
A haemodynamic monitoring and control task was used to evaluate the ecological approach to interface design for complex high-technology environments. Guidelines proposed by Bennett and Flach (1992) were used to design multilevel displays that made visible (a) anatomical constraints, and (b) causal constraints on haemodynamic systems. ⋯ Critical care nurses and nursing students observed changes in pressures and flow corresponding to certain disease states and corrected those states using simulated drugs. For both groups, speed and accuracy were progressively improved by the enhanced, multilevel displays.
-
Two experiments are reported which examined operators' trust in and use of the automation in a simulated supervisory process control task. Tests of the integrated model of human trust in machines proposed by Muir (1994) showed that models of interpersonal trust capture some important aspects of the nature and dynamics of human-machine trust. Results showed that operators' subjective ratings of trust in the automation were based mainly upon their perception of its competence. ⋯ There was high positive correlation between operators' trust in and use of the automation; operators used automation they trusted and rejected automation they distrusted, preferring to do the control task manually. There was an inverse relationship between trust and monitoring of the automation. These results suggest that operators' subjective ratings of trust and the properties of the automation which determine their trust, can be used to predict and optimize the dynamic allocation of functions in automated systems.