Auditory displays, which can be as basic as buzzers or as advanced as computer-generated ‘synthetic speech’, are primarily used to provide warnings. They are used in situations where visual displays are not adequate, i.e., when an urgent message or one that is continuously changing (as is the case with aircraft flight path information) or one that deals with a specific moment (such as a gun fired to start a race) needs to be conveyed. They are also ideal for work situations in which the operator needs to move in all directions and in dark environments where visual information would be difficult to see.
In order for auditory displays to be effective, Edworthy (1994) suggests that they must be at the appropriate sound and volume level, i.e., neither so soft that they go unheard, nor so loud that they distract workers. In addition to this, auditory warning displays need to be psychologically appropriate. For instance, short bursts of noise are more likely to be perceived as warning signals than a single bell-type sound.
Once the machine has shown output via displays, the worker engages in a three-step information processing and decision making process. The first step is the perceptual stage, in which the worker receives visual and auditory data through the senses.
The second step is the cognitive stage, in which the worker classifies and interprets the sensory input. The worker first compares the sensory input to some cognitively stored information, including past experience with the machine and knowledge gleaned from training Then, it is classified it into a category that corresponds with the kind of information provided, e.g., a buzzer may be classified as either ‘status information’ or ‘warning’. Finally, the worker refers to the specific language used by the machine to interpret its messages.
The third step is the action stage, in which the worker uses memory and/or training to select one of several courses of action that can be taken, and communicates the decision by manipulating controls (Kantowitz, 1989).
Machine controls are mechanical devices such as knobs that an operator uses to control machine functions.
One type of machine controls are keyboard controls, which can take the form of an alphabetic or numeric keyboard. Numeric keyboards are either arranged as a string of numbers at the top row of a keyboard, or as three rows of three digit keys in either ascending (as with telephone) or descending order (as is the case with calculators). Alphabetic keyboards can either take the QWERTY format, in which vowels are scattered all over the keyboard, or the DVORAK one, in which the vowels are arranged in the home row and are all activated by the left hand. The latter is more efficient for touch typing as over 3000 words can be typed using letters from the home row alone (as opposed to the 120 words using QWERTY keyboard), which may increase typing speed by 5 to 20 percent (Sander et al., 1993).
Certain basic principles have to be followed in design and selection of controls in order for operator decisions to be communicated effectively. First, controls should be matched to the operator’s body. To prevent operator’s hands from being overloaded, only controls requiring great precision should be hand-operated; other simple operations should be controlled by foot. Second, control movements should mirror the machine actions they produce. Third, related controls should be combined so that in one action, the operator can change the operation of both systems. Fourth, controls should be clearly marked for rapid identification. Not only can they be visually recognized, some controls may require shape-coded controls that can be quickly recognized by touch. Fifth, the placement of important controls on similar machine systems should be standardized, especially when a worker is required to alternate between several similar machines regularly. Sixth, controls, especially emergency controls, should be adequately spaced and arranged to avoid unintentional activation.
Upon the conclusion of the action stage, the manipulation of the controls becomes the machine’s input, which causes the machine to perform the requested action. Subsequent changes in the operating status are then communicated to the operator via displays, and the cycle continues.
Apart from designing operator-machine system, human factors psychologists are also concerned with minimizing the number of errors produced by them. Swain et al. (1983) outline four main types of errors produced by operator-machine systems: omission errors (the failure to do something), commission errors (the incorrect performance of an act), sequence errors (the performance of series of tasks out of order) and timing errors (the performance of an act either too quickly or too slowly).
There are two main approaches of dealing with human errors. One of these is the personnel approach, which is a two-pronged method involving the selection of only those workers who possess the skills and expertise required to operate the system flawlessly and training workers to safely perform their jobs with minimum number of errors. The second is the design approach, which involves designing machines, procedures and environments that reduce the likelihood of errors and the consequences of those errors.
Another important aspect of human factors is workspace design, which is the endeavor to create efficient, productive and comfortable work setting by the careful design and arrangement of equipment, space and machinery within a work environment.
Three main types of individual work stations exist, each of which are tailored to meet specific needs. One of them is the seated workstation, which are used when all machines needed to perform the job are comfortably within reach and the work involves no heavy lifting or forceful movements. Examples of such jobs include clerical tasks and fine assembly work. The second type of workstation is the standing workstation, which is ideal for work involving handling of heavy objects and the worker’s frequent movement from place to place. Examples of such jobs include large assembly work in factories and packaging and wrapping operations. The third type is the combined work station, that are ideal for jobs involving multiple tasks, some performed while seated while others while standing. It is also ideal for jobs involving the worker doing seated work but most repeatedly reach high or low distances. An example of such a job includes that of a draftsman.
McCormick et al. (1993) have outlined some basic principles governing the location and arrangement of machines and space. One of these is the importance principle, according to which the most important operations should take place in a central location and crucial displays should be placed directly in front of the operator. Another rule is the frequency-of-use principle, which stipulates that machines or controls that are used often should be conveniently located. The functional principle states that functionally related components should be grouped together. The sequence-of-use principle requires items to be placed in the order they will be used.
In summary, human factors in work design concerns with the design of work machines, systems and environments.
- Giving reasons for your answer, suggest an efficient workspace design for a student.
An efficient workspace design for a student could take the form of a seated workstation, comprising of a desk and seat. This is an appropriate choice of workstation for two reasons: first, all books and supplies needed by the student can be comfortably placed within the reach of the seated student; second, the work of a student does not entail heavy lifting or forceful movements.
The desk should be spacious enough to accommodate the storage of all necessary items of use, including books, stationery and such devices as table clocks, lamps, computers and related hardware. To avoid the desk taking too much space, the desk should incorporate various compartments such as shelves, cabinets and drawers, for the storage of books, writing material, and stationery, leaving the desk empty for the computer hardware and items of immediate use. These compartments should be of varying shapes and sizes, so that all items to be stored can be grouped by function – as stipulated by the functional principle – resulting in an organized, clutter-free environment for the student
The seat should be designed so that the student is at the proper height and distance from the desk. They should also be fashioned so that a student who is seated for long periods do not experience back or leg strain.
Also, the workspace should not only be designed for functional efficiency, but its characteristics must also be psychologically appealing (Donald, 1994). Therefore, it should be located in a place where extraneous noises are at their minimum. Also, the area should be properly illuminated, preferably with fluorescent lighting that provides increased illumination, better light distribution and reduced energy cost, as compared to incandescent lighting. Also, care must be taken not to overlight the work area.