Workload: Difference between revisions

To distinguish the two types, the term 'mental workload' (MWL) is often preferred, clearly indicating the latter type, which refers to the workload experienced by a human, regardless of the task's difficulty. This is because the same underlying task might generate two distinct mental responses and experiences, thus, different cognitive load amounts, even if executed by the same person. Many definitions of mental workload have been proposed in the years.<ref name="Longo 2022">{{cite journal | author = Longo L., Wickens C. D., Hancock G. and Hancock P. A. | year = 2022 | title = Human Mental Workload: A Survey and a Novel Inclusive Definition| journal = Front. Psychol. | volume = 12 | doi = 10.3389/fpsyg.2022.883321 | pmid = 35719509 | doi-access = free | pmc = 9201728 | hdl = 10147/635016 | hdl-access = free }}{{Creative Commons text attribution notice|cc=by4|from this source=yes}}</ref>

The assessment of operator workload has a vitalstrong impact on new human-machine systems [[design]]. By evaluating operator workload during the design of a new [[system]], or [[iteration]] of an existing system, problems such as workload [[bottleneck (project management)|bottleneck]]s and [[Mechanical overload (engineering)|overload]] can be identified. As the human operator is a central part of a human-machine system, correcting these problems is necessary forto the operation ofoperate safe and efficient systems. An [[operating budget]] may include estimates of the expected workload for a specific activity. 'Workload' or 'cognitive load' is often confused with '[[cognitive load theory]]'. The latter is referred to as the actual construct of Cognitive Load (CL), or mental workload (MWL). In contrast, the former is referred to a specific [[Cognitivism (psychology)|cognitivist]] learning theory within the larger field of [[pedagogy]] and [[instructional design]].

This theory was also used to determine [[horse power]] (hp), which was defined as the amount of work a horse could do with a given load over time. The wheel that the horse turned in Watt's original experiment put a certainspecific load on the horse's muscles, and the horse could do a certain amount of work with this load in a minute. Provided the horse was a perfect machine, it would be capable of a constant maximum workload. Increasing the load by a given percentage would decrease the possible work done by the same percentage so that it would still equal "1 hp". Horses are, obviously, not perfect machines and, over short periods, are capable of as much as 14&nbsp;hp, and over long periods of exertion, output an average of less than 1&nbsp;hp.

The theory can also be applied to [[automobiles]] or other machines, which are slightly more "perfect" than animals. Making a car heavier, for instance, increases the load that the engine must pull. Likewise, making it more aerodynamic decreases drag, which also acts as a load on the car. Torque can be thought of asconsidered the ability to move a load, and the revs are how much work it can do with that load in a given amount of time. Therefore, torque and revs together create kilowatts or total power output. Total output can be related to the "workload" of the engine/car, or how much work it can do with a given load. As engines are more mechanically perfect than animals' muscles and do not fatigue similarly, they will conform much more closely to the formula that if you apply more load, they will do less work, and vice versa.

In an occupational setting, dealing with workload can be stressful and serve as a [[stressor]] for employees. There are threeThree aspects of workload that can be stressful.

Workload as a work demand is a major component of the demand-control model of stress.<ref>{{cite journal | author = Karasek R. A. | year = 1979 | title = Job demands, job decision latitude, and mental strain-implications for job redesign | journal = Administrative Science Quarterly | volume = 24 | issue = 2| pages = 285–308 | doi=10.2307/2392498| jstor = 2392498 }}</ref> This model suggests that jobs with high demands can be stressful, especially when the individual has low control over the job. In other words, control serves as a buffer or protective factor when demands or workload is high. This model was expanded into the demand-control-support model, thatwhich suggests that the combination of high control and high social support at work buffers the effects of high demands.<ref>{{cite journal | author = Johnson J. V., Hall E. M. | year = 1988 | title = Job strain, work place social support, and cardiovascular disease: A cross-sectional study of a random sample of the Swedish working population | journal = American Journal of Public Health | volume = 78 | issue = 10| pages = 1336–1342 | doi=10.2105/ajph.78.10.1336| pmid = 3421392 | pmc = 1349434}}</ref> A 2019 survey by Cartridge People identified workload as the main cause of occupational stress.<ref>{{Cite web |title=What's Causing UK Workers Stress in 2019 |url=https://www.cartridgepeople.com/info/blog/uk-workers-stress-statistics |access-date=2023-10-28 |website=www.cartridgepeople.com |language=en}}</ref>

There is no one agreed definition of mental workload and consequently not one agreed method of assessing or modelling it .<ref name="Longo 2022"/>. One example definition by Hart and Staveland (1988) describes workload as "the perceived relationship between the amount of mental processing capability or resources and the amount required by the task". A more generally applicable operational definition of workload is that "Mental workload (MWL) represents the degree of activation of a finite pool of resources, limited in capacity, while cognitively processing a primary task over time, mediated by external stochastic environmental and situational factors, as well as affected by definite internal characteristics of a human operator, for coping with static task demands, by devoted effort and attention" .<ref name="Longo 2022"/>.

Wickens' (1984) multiple resource theory (MRT) model <ref>Wickens, C.D. (1984). "Processing resources in attention", in R. Parasuraman & D.R. Davies (Eds.), ''Varieties of attention'', (pp. 63–102). New York: Academic Press.</ref> is illustrated in figure 1:

Wickens' theory views performance decrement as a shortage of these different resources and describes humans as having limited capability for processing information. Cognitive resources are limited, and a supply and demand problem occurs when the individual performs two or more tasks that require a single resource (as indicated by one box on the diagram). Excess workload caused by a task using the same resource can cause problems and result in, errors, or slower task performance. For example, if the task is to dial the phone, then no excess demands are being placed on any one component. However, if another task is being performed at the same timesimultaneously that makes demands on the same component(s), the result may be an excess workload.

The relationship between workload and performance is complex. It is not always the case that as workload increases, performance decreases. Performance can be affected by workload being too high or too low (Nachreiner, 1995). SustainedA sustained low workload (underload) can lead to boredom, loss of situation awareness and reduced alertness. Also, as workload increases, performance may not decrease as the operator may have a strategy for handling task demands.

Like Wickens, McCracken and Aldrich (1984), like Wickens, describe the processing, not as one central resource but as several processing resources: visual, cognitive, auditory, and psychomotor (VCAP). All tasks can be decomposed into these components.

They developed rating scales for each of the VCAP componentscomponent, which provide a relative rating of the degree to which each resource component is used.

Joseph Hopkins (unpublished) developed a training methodology,. where theThe background to his training theory is that complex skills are, in essence, resource conflicts where training has removed or reduced the conflicting workload demands, either by higher -level processing or by predictive time sequencing. His work is in effect based on Gallwey (1974) and Morehouse (1977). The theory postulates that the training allows the different task functions to be integrated into one new skill. An example of this is learning to drive a car. Changing gear and steering are two conflicting tasks (i.e. both require the same resources) before they are integrated into the new skill of "driving". An experienced driver will not need to think about what to do when turning a corner (higher level processing) or alternatively may change gear earlier than required to give sufficient resources for steering roundaround the corner (predictive time sequencing).

With any attempt at creating a workload model, the process begins with understanding the tasks to be modelled. This is done by creating a task analysis that defines:

These numerical values against each resource type of resource are then entered into the workload model. The model sums the workload ratings within each resource and across concurrent tasks. The critical points within the task are therefore identified. When proposals are made for introducing new devices onto the current baseline activities, thethis impact of this can then be compared to the baseline.

Possibly oneOne of the most advanced workload models was possibly developed by K Tara Smith (2007):. thisThis model integrated the theories of Wickens, McCracken and Aldrich and Hopkins to produce a model that not only predicts the workload for an individual task but also indicates how that workload may change given the experience and training level of the individuals carrying out that task.

* Does the operator have the capability to perform the required tasks?

* Does the operator have enough spare capacity to cope with emergency situationsemergencies?

* Can the task or equipment be altered to increase the amount of spare capacity?

===Cognitive workload in time -critical decision-making processes===

It is well accepted that there is a relationship between the media by which information is transferred and presented to a [[decision maker]] and their cognitive workload. During times of concentrated activity, single-mode information exchange is a limiting factor. Therefore, the balance between the different information channels (most commonly considered to be visual processing and auditory, but could also include haptic, etc.) has a direct effectdirectly onaffects cognitive workload (Wickens 1984). In a [[time-critical]] decision situation, this workload can lead to [[human error]] or delayed decisions to accommodate the processing of the relevant information. (Smith, K.T. & Mistry, B. 2009).<ref>Smith, K.T., Mistry, B (2009) Predictive Operational Performance (PrOPer) Model. Contemporary Ergonomics 2009 Proceedings of the International Conference on Contemporary Ergonomics 2009 http://www.crcnetbase.com/doi/abs/10.1201/9780203872512.ch28</ref>

* '''workload debt''' - which is when an individual's cognitive workload is too high to complete all relevant tasks in the time available, and they decide (either consciously or subconsciously) to postpone one or more tasks (usually low priority tasks) to enable them to make the decisiondecide inon the required timeframe.

* '''workload debt cascade''' - which is when, because of the high workload, the postponed tasks mount up so that the individual cannot catch up with the tasks that they are required to do, causing failure in subsequent activities.