Practice English Speaking&Listening with: Workload

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The term workload can refer to a number of different yet related entities.

However, it is clear that cognitive workload results from mental processes

when performing tasks, depending on the users's capabilities and the task

demands. An amount of labor

Workload is the amount of work an individual has to do. There is a

distinction between the actual amount of work and the individual's perception of

the workload. Workload can also be classified as quantitative or

qualitative. The assessment of operator workload has

a vital impact on the design of new human-machine systems. 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,

the correction of these problems is necessary for the operation of safe and

efficient systems. An operating budget may include

estimates of the expected workload for a specific activity. Work loads can vary

in many different situations, but the average workload is average.

Quantified effort Workload can also refer to 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 anecotal evidence and scientific

research has shown that it is the total "workload" that is important to muscle

growth, as opposed to just the load, just the volume, or "time under

tension". In these and related uses of the word, "workload" can be broken up

into "work+load", referring to the work done with a given load. In terms of

weights training, the "load" refers to the heaviness of the weight being

lifted, and "work" refers to the volume, or total number of reps and sets done

with that weight. This theory was also used to determine

horse power, 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 certain 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, so

increasing the load by a given percentage would result in the possible

work done decreasing by the same percentage, so that it would still equal

"1 hp". Horses are, obviously, not perfect machines and over short time

periods are capable of as much as 14 hp, and over long periods of exertion output

an average of less than 1 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 acts

as a load on the car as well. Torque can be thought of as the ability to move

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, which can be related to the "workload" of the engine/car, or how

much work it can do with a given amount of load. As engines are more

mechanically perfect than animals' muscles, and do not fatigue in the same

way, they will conform much more closely to the formula that if you apply more

load, they will do less work, and vice versa.

Occupational stress In an occupational setting, dealing with

workload can be stressful and serve as a stressor for employees. There are three

aspects of workload that can be stressful.

Quantitative workload or overload: Having more work to do than can be

accomplished comfortably. Qualitative workload: Having work that

is too difficult. Underload: Having work that fails to use

a worker's skills and abilities. Workload has been linked to a number of

strains, including anxiety, physiological reactions such as

cortisol, fatigue, backache, headache, and gastrointestinal problems.

Workload as a work demand is a major component of the demand-control model of

stress. 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 that

suggests that the combination of high control and high social support at work

buffers the effects of high demands. As a work demand, workload is also

relevant to the job demands-resources model of stress that suggests that jobs

are stressful when demands exceed the individual's resources to deal with

them. Theory and modelling

Another aspect to workload is the mathematical predictive models used in

human factors analysis; generally to support the design and assessment of

safety-critical systems. There is no one agreed definition of

workload and consequently not one agreed method of assessing or modelling it. One

example definition by Hart and Staveland describes workload as "the perceived

relationship between the amount of mental processing capability or

resources and the amount required by the task". Workload modelling is the

analytical technique used to measure and predict workload. The main objective of

assessing and predicting workload is to achieve evenly distributed, manageable

workload and to avoid overload or underload.

= Theories = Wickens multiple resource theory model

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 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. 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 time that makes demands on the same

component(s), the result may be 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. Sustained low workload 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. Wickens theory allows system designers

to 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.

McCracken and Aldrich, like Wickens, describe processing not as one central

resource but several processing resources: visual, cognitive, auditory,

and psychomotor. All tasks can be decomposed into these components.

The visual and auditory components are external stimuli that are attended to.

The cognitive component describes the level of information processing

required. The psychomotor component describes the

physical actions required. They developed rating scales for each of

the VCAP components, which provide a relative rating of the degree to which

each resource component is used. Joseph Hopkins developed a training

methodology, where the 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 and

Morehouse. 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 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 or alternatively may

change gear earlier than required to give sufficient resources for steering

round the corner. = Creating a model =

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: 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 a sufficient level to allow realistic

physical and mental workload values to be estimated and to determine which

resources are required for each task visual, auditory, cognitive and

psychomotor. A numerical value can be assigned to each based on the scales

developed by McCracken and Aldrich. These numerical values against each 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 the

impact of this can then be compared to the baseline. Possibly one of the most

advanced workload models was developed by K Tara Smith: this model integrated

the theories of Wickens, McCracken and Aldrich and Hopkins to produce a model

that not only predicts 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 answer the following types of questions: Eisen, P.S and

Hendy, K.C.: Does the operator have capability to

perform the required tasks? Does the operator have enough spare

capacity to take on additional tasks? Does the operator have enough spare

capacity to cope with emergency situations?

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

Can the task or equipment be altered to increase/decrease the amount of mental

workload? How does the workload of a new system

compare to the old system? = 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 has a direct effect

on cognitive workload. In a time-critical decision situation, this

workload can lead to human error or delayed decisions to accommodate the

processing of the relevant information.. Work conducted by K Tara Smith has

defined some terms relating to the workload in this area. The two main

concepts relating to workload are: workload debt - which is when an

individuals cognitive workload is too high to complete all relevant tasks in

the time available and they decide to postpone one or more tasks to enable

them to make the decision in 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. See also

Cognitive load Manpower

Situation Awareness Notes

The Description of Workload