workload là gì

The term workload can refer to tướng several different yet related entities.

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An amount of labor[edit]

An old definition refers to tướng workload as the amount of work an individual has to tướng tự.[1] There is a distinction between the actual amount of work and the individual's perception of the workload. [1] To distinguish the two types, the term 'mental workload' (MWL) is often preferred, clearly indicating the latter type, which refers to tướng 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.[2] A more recent and operational definition 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".[2] This definition has emerged from a systematic review of the construct of mental workload by analysing many published research works and all the ad-hoc definitions that have emerged in the last 60 years. It has also been influenced by the Multiple Resource Theory, described below, and the notion of human, multiple resources. [3]

The assessment of operator workload has a strong 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 bottlenecks and overload can be identified. As the human operator is a central part of a human-machine system, correcting these problems is necessary to tướng operate 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 tướng as the actual construct of Cognitive Load (CL), or mental workload (MWL). In contrast, the former is referred to tướng a specific cognitivist learning theory within the larger field of pedagogy and instructional design.

Quantified effort[edit]

Workload can also refer to tướng the total energy output of a system, particularly of a person or animal performing a strenuous task over time. One particular application of this is weight lifting/weights training, where both anecdotal evidence and scientific research have shown that it is the total "workload" that is important to tướng muscle growth, as opposed to tướng just the load, just the volume, or "time under tension". In these and related uses, "workload" can be broken up into "work+load", referring to tướng the work done with a given load. In terms of weights training, the "load" refers to tướng the heaviness of the weight being lifted (20 kg is a more significant load phàn nàn 10 kg), and "work" refers to tướng the volume, or the total number of reps and sets done with that weight (20 reps are more work phàn nàn ten reps, but two sets of 10 reps are the same work as 1 mix of đôi mươi reps, its just that the human toàn thân cannot tự 20reps of heavy weight without a rest, so sánh its best to tướng think of 2x10 as being đôi mươi reps, with a rest in the middle).

This theory was also used to tướng determine horse power (hp), which was defined as the amount of work a horse could tự with a given load over time. The wheel that the horse turned in Watt's original experiment put a specific load on the horse's muscles, and the horse could tự 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 sánh that it would still equal "1 hp". Horses are not perfect machines and, over short periods, are capable of as much as 14 hp, and over long periods of exertion, output an average of less phàn nàn 1 hp.

The theory can also be applied to tướng automobiles or other machines, which are slightly more "perfect" phàn nàn animals. Making a siêu xe 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 siêu xe. Torque can be considered the ability to tướng move a load, and the revs are how much work it can tự 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 tướng the "workload" of the engine/car or how much work it can tự with a given load. As engines are more mechanically perfect phàn nàn animals' muscles and tự not fatigue similarly, they will conform much more closely to tướng the formula that if you apply more load, they will tự less work, and vice versa.

Occupational stress[edit]

In an occupational setting, workload can be stressful and serve as a stressor for employees. Three aspects of workload can be stressful.

Quantitative workload or overload: Having more work to tướng tự phàn nàn can be accomplished comfortably.
Qualitative workload: Having work that is too difficult.
Underload: Having work that fails to tướng use a worker's skills and abilities.[4]

Workload has been linked to tướng a number of strains, including anxiety, physiological reactions such as cortisol, fatigue,[5] backache, headache, and gastrointestinal problems.[6]

Workload as a work demand is a major component of the demand-control model of stress.[7] 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, which suggests that the combination of high control and high social tư vấn at work buffers the effects of high demands.[8]

As a work demand, workload is also relevant to tướng the job demands-resources model of stress that suggests that jobs are stressful when demands (e.g., workload) exceed the individual's resources to tướng giảm giá khuyến mãi with them.[9][10]

Theory and modelling[edit]

There is no one agreed definition of mental workload and consequently not one agreed method of assessing or modelling it.[2] 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".[2]

Workload modelling is the analytical technique used to tướng measure and predict workload. The main objective of assessing and predicting cognitive workload is to tướng achieve an evenly distributed, manageable workload and to tướng avoid overload or underload. Another aspect of workload is the mathematical predictive models used in human factors analysis to tướng tư vấn the design and assessment of safety-critical systems.


Figure 1: Wickens' Multiple Resource Theory (MRT) Model

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Wickens' (1984) multiple resource theory (MRT) model [11] is illustrated in figure 1:

Wickens' MRT proposes that the human operator does not have one single information processing source that can be tapped but several different pools of resources that can be tapped simultaneously. Each box in figure 1 indicates one cognitive resource. Depending on the nature of the task, these resources may have to tướng process information sequentially if the different tasks require the same pool of resources or can be processed in parallel if the task requires different resources.

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, errors, or slower performance. For example, if the task is to tướng dial the phone, then no excess demands are placed on any component. However, if another task is being performed simultaneously that demands 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). A sustained low workload (underload) can lead to tướng 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.

Wickens' theory allows system designers to tướng predict when:

  • Tasks can be performed concurrently.
  • Tasks will interfere with each other.
  • Increases in the difficulty of one task will result in a loss of performance of another task.

Like Wickens, McCracken and Aldrich (1984) 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.

  • The visual and auditory components are external stimuli that are attended to tướng.
  • The cognitive component describes the level of information processing required.
  • The psychomotor component describes the physical actions required.

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

Joseph Hopkins (unpublished) developed a training methodology. The background to tướng 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 based on Gallwey (1974) and Morehouse (1977). The theory postulates that the training allows the different task functions to tướng be integrated into one new skill. An example of this is learning to tướng drive a siêu xe. 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 tướng think about what to tướng tự when turning a corner (higher level processing) or may change gear earlier phàn nàn required to tướng give sufficient resources for steering around the corner (predictive time sequencing).

Creating a model[edit]

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

  • The sequence of tasks performed by individuals and team members.
  • The timing and workload information associated with each task.
  • Background scenario information.

Each task must be defined to tướng a sufficient level to tướng allow realistic physical and mental workload values to tướng be estimated and to tướng determine which resources (or combination of resources) are required for each task – visual, auditory, cognitive and psychomotor. A numerical value can be assigned to tướng each based on the scales developed by McCracken and Aldrich.

These numerical values against each resource type 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, this impact can then be compared to tướng the baseline. One of the most advanced workload models was possibly developed by K Tara Smith (2007). This model integrated the theories of Wickens, McCracken and Aldrich and Hopkins to tướng 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. Workload assessment techniques are typically used to tướng answer the following types of questions: Eisen, P..S and Hendy, K.C. (1987):

  • Does the operator have the capability to tướng perform the required tasks?
  • Does the operator have enough spare capacity to tướng take on additional tasks?
  • Does the operator have enough spare capacity to tướng cope with emergencies?
  • Can the task or equipment be altered to tướng increase spare capacity?
  • Can the task or equipment be altered to tướng increase/decrease the amount of mental workload?
  • How does the workload of a new system compare to tướng the old system?

Cognitive workload in time-critical decision-making processes[edit]

It is well accepted that there is a relationship between the truyền thông media by which information is transferred and presented to tướng 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 visual processing and auditory, but could also include haptic, etc.) directly affects cognitive workload (Wickens 1984). In a time-critical decision situation, this workload can lead to tướng human error or delayed decisions to tướng accommodate the processing of the relevant information. (Smith, K.T. & Mistry, B. 2009).[12] Work conducted by K Tara Smith has defined some terms relating to tướng the workload in this area. The two main concepts relating to tướng workload are:

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  • workload debt - which is when an individual's cognitive workload is too high to tướng complete all relevant tasks in the time available, and they decide (either consciously or subconsciously) to tướng postpone one or more tasks (usually low priority tasks) to tướng enable them to tướng decide on the required timeframe.
  • workload debt cascade - when, because of the high workload, the postponed tasks mount up so sánh that the individual cannot catch up with the tasks they are required to tướng tự, causing failure in subsequent activities.

See also[edit]

  • Cognitive load
  • Manpower
  • Situation Awareness


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