Human performance effects

The Edgewood tests, conducted over a 20-year period ending in 1975, were intended to investigate the immediate and short-term human-performance effects of short-term exposure to various chemicals with warfare potential and the subjects responses to therapy for such effects. 

Regulinksi, T. L., Askren, W. B., Stochastic Modeling of Human Performance Effectiveness Functions, Proceedings of the Annual Reliability and Maintainability Symposium, 1972, pp. 407-416. 

The first component of the systems approach to error reduction is the optimization of human performance by designing the system to support human strengths and minimize the effects of human limitations. The hiunan factors engineering and ergonomics (HFE/E) approach described in Section 2.7 of Chapter 2 indicates some of the techniques available. Design data from the human factors literature for areas such as equipment, procedures, and the human-machine interface are available to support the designer in the optimization process. In addition the analytical techniques described in Chapter 4 (e.g., task analysis) can be used in the development of the design. 

It is important, however, not to take this analogy too far. In general, the performance of a piece of hardware, such as a valve, will be much more predictable as a function of its operating conditions than will human performance as a function of the PIFs in a situation. This is partly because human performance is dependent on a considerably larger number of parameters than hardware, and only a subset of these will be accessible to an analyst. In some ways the job of the human reliability specialist can be seen as identifying which PIFs are the major determinants of human reliability in the situation of interest, and which can be manipulated in the most cost-effective manner to minimize error. 

In the nex - section of this chapter, some application areas for PIF analyses will be described. This will be followed by a classification scheme for PIFs based on the demand-resource mismatch model of error described in Chapter 1, Section 1.6. Subsequent sections will describe each of the PIF categories in turn, followed by examples where appropriate. These sections are followed by a discussion of the effects of interactions between PIFs and the implications of high levels of stress in emergencies for human performance. 

Unlike the hardware component in a system, human performance is much more variable and difficult to predict. The same combination of input conditions will produce nearly similar effects on hardware. This is not the case for humans who will process the inputs in the light of their intentions and biases in a unique manner. 

The classification structure for PIFs used in this chapter is based on the model of human error as arising from a mismatch between demands and resources which was described in Chapter 1, Section 1.6 (Figure 1.6). In this model demands were seen as requirements for human performance which arise from the characteristics of the process environment (e.g., the need to monitor a panel or to be able to fix a seal in a flange) and the nature of the human capabilities to satisfy these demands (e.g., skills of perception, thinking, and physical action). These demands are met by the individual and group resources of personnel and the extent to which the design of the task allows these resources to be effectively deployed. Where demands exceeded resources, errors could be expected to occur. 

Most of the research on the effects of these stressors on human performance has been done on simple laboratory tasks rather than actual work situations. As a result, the extent that such findings can carry over to tasks in the CPI is debatable. In addition, most of these studies have examined the effect of a single stressor (e.g., noise or heat) only, rather than the combined effect. Nevertheless, some useful guidelines about optimal levels of these stressors are available in the ergonomics literature (e.g., McCormick and Sanders, 1983 Salvendy, 1987). 

The effects of chronic sleep deprivation or cumulative minor sleep losses have been relatively under investigated. Little is known about the relationships among the size of the sleep deficit, its rate of accumulation, the amount and timing of optimum recovery sleep, and their effect on human performance and productivity. 

The impact of the system design on human performance should be examined during this phase. The designer should consider whether or not the operator will be able to keep the system operating correctly under normal conditions and is he or she able to effectively handle unusual conditions, returning them to normal operating conditions. Observation of persormel and discussions with them are effective ways that should be employed in this phase. Where necessary, appropriate modifications should be made to the system to ensure proper performance. 

Performance-Influencing Factors Factors that influence the effectiveness of human performance and hence the likelihood of errors. 

A series of studies conducted in the late 1970s at Ball State University s Human Performance Laboratory by Costill and associates6163 has established caffeine as an effective ergogenic aid for the enhancement of endur-... 

Clubley, M., Bye, C. E., Henson, T. A., Peck, A. W. and Riddington, C. J., Effects of caffeine and cyclizine alone and in combination on human performance, subjective effects and EEG activity. British Journal of Clinical Pharmacology 7 157-63, 1979. 

Sawyer, D. A., Julia, H. L., Turin, A. C., Caffeine and human behavior Arousal, anxiety, and performance effects. Journal of Behavioral Medicine 5(4), 415-439, 1982. 

Chait LD and Pierri J (1992). Effect of smoked marijuana on human performance A critical review. In A Murphy and J Bartke (eds), Marijuana/Cannabinoids Neurobiology and... 

Crowley JS, Wesensten N, Kamimori G, Devine J, Iwanyk E and Balkin T (1992). Effect of high terrestrial altitude and supplemental oxygen on human performance and mood. Aviation, Space and Environmental Medicine, 63, 696-701. 

Heishman SJ, Taylor RC and Henningfield JE (1994). Nicotine and smoking A review of effects on human performance. Experimental and Clinical Psychopharmacology, 2, 345-395. 

Lieberman HR, Wurtman RJ, Emde GC, Roberts C and Coviella LG (1987). The effects of low doses of caffeine on human performance and mood. Psychopharmacology, 92, 308-312. 

The single most influence effect of human performance is attitude. Attidtude is the mind set, point of view and the way we look at things. The way we look at things is the partly responsible for the nature of our behavior and performance. Some of the more common attitudes which influence accidental behavior are listed below ... 

Caffeine increases the capacity of skeletal muscle. This effect is probably due to the release of intracellular Ca2+, and is observable in human performance. The contribution of central effects is also likely. Whether caffeine actually benefits exercise is contested (Spriet 1995 Dodd et al. 1993). Research does not consistently support caffeine enhancement of performance during high-intensity, short-term exercise. There is some evidence to suggest benefit during prolonged, moderate-intensity exercise. 

Franks FIM, Flagedorn FI, Flensley VR, Flensley WJ, Starmer GA. (1975). The effect of caffeine on human performance, alone and in combination with ethanol. Psychopharmacologia. 45(2) 177-81. Franks P, Flarp J, Bell B. (1989). Randomized, controlled trial of clonidine for smoking cessation in a primary care setting. JAMA. 262(21) 3011-13. 

Fourtillan JB, Brisson AM, Girault J, Ingrand I, Decourt JP, Drieu K, Jouenne P, Biber A. (1995). [Pharmacokinetic properties of bilobalide and ginkgolides A and B in healthy subjects after intravenous and oral administration of Ginkgo biloba extract (EGb 761)]. Therapie. 50(2) 137-44. Frewer U. (1990). The effect of betel nut on human performance. PNG MedJ. 33(2) 143-5. 

Belgrave BE, Bird KD, Chesher GB, Jackson DM, Lubbe KE, Starmer GA, Teo RK. (1979). The effect of (—) trans-delta9-tetrahydrocannabinol, alone and in combination with ethanol, on human performance. Psychopharmacology (Berlin). 62(1) 53-60. 

The effects of scopolamine on representative human performance tests. Technical Report 1, Contract No. DA-18-035-AMC-282[A], 1965. 

Elkin EH, Freedle RO, Cott HP Van, Fleishman EA Effects of drugs on human performance. The effects of scopolamine on... 

Include specific equipment identification, because omission can cause problems for readers in other process units or facilities who may have the same equipment and remain imaware of its hazards. Avoid downplaying human performance factors when drafting the report. There is a natural hesitancy to criticize or address normally encountered performance limitations or errors. Effects of fatigue from working excessive overtime are not always addressed in the written report. If these human performance factors are neglected, the error may be repeated. All facts of the incident must be considered relevant. 

---