Frederique Krupa
Spring 1994

 

Introduction to Human Factors

Ergonomics Science of Work, is a field of technology that considers human capabilities and limitations in the design of machines and objects that people use, the work processes they follow and the environments in which they operate. It is also refered to as
biotechnology, human engineering, human factors engineering. Because it is multidisciplinary, human factors professionals can engage and specialize in:
1. PHYSICAL physiological, biomechanical, anthropometry
2. PSYCHOLOGY information processing, attention and mental workloads, cognition, perception, stress
3. SOCIOLOGY Maslow's Theory of Motivations and Hierarchy of Needs

The term did not become widely used until WWII, but human factors concerns have been around much longer. Systematic interest in physiology has been around since the Renaissance. A tract from the 1660's describe worker injuries and fatigue caused by poor working condition. The interest in human capabilities and limitations is not as altruistic as it first seems. The real interest besides making sure the worker doesn't get hurt, maimed or killed is to increase production and efficiency. (and nowdays, to avoid lawsuits and workers' comp claims)

The Goals of Ergonomics
1. meet most people's capacity
2. maximize human perception
3. reduce human error
4. optimize worker and workplace interaction
5. provide flexibility to accomodate individual differences


The first person to suggest division of labor to enhance efficiency was none other than Adam Smith, author of a Wealth of Nations in 1772 and father of capitalism as we know it. England was in the throes of the Industrial Revolution, (America was too busy trying to obtain indepence) and at this time the steam engine and all these amazing new machines were radically transforming the production process from one where a single person frequently designed, built and sold an object to one that required large numbers of people with increasingly specialized skills (ie kids with their small hands were just perfect for the task of fixing the new automated textile looms). Designing as an act separate from making came about as a result of this.

Charles Babbage suggested the same in his book the Economy of Manufacture in 1832, where he suggests that skill levels required for each job be used to determine the wage of that job and that scientific methods be used to analyse business problems, especially Time and Motion Study. This was the first link to Scientific Management, which I'll talk about later.

The drive for production efficiency was not fully realized in the creation of complex objects until 1913 when Ford designed the mile-long assembly line to produce his Model T at the Highland Park Plant. What this drive for efficiency was about expanding business opportunities and increasing standard of living for Americans. So on one hand, the base price of the Model T went from $850 in 1908 when there were 6400 cars made to $350 in 1917 when 750,000 cars were made. In 1923, Ford produced over 2 million cars and the price dropped to $300. The cars became more affordable to a wider cross section of the population, but employment figures at the Ford plant did not expand much, especially considering the production output. Mechanization had restructured the industrial plant and now management`s task was to make the workers fit the machine mold. The working environment was designed to speed production, not for the well being of the workers.

BUT BACK TO LATE 1880'S, One of the first social scientists to try their hand at "Scientific Management" was Frederick Taylor, a Philadelphia engineer(1856-1915) who figured a way to increase efficiency at Bethlehem steel (to shovel coal into the furnaces.) Scientific Management sought to gather and analyze the great mass of traditional knowledge that had always been in the mind of the workman, and this robbed the worker of the control he previously enjoyed over the methods of his work by measuring human work potential and rationalizing and standardizing jobs. Taylor was content to break down the worker's time down into smallers tasks and time each with a stopwatch. He would then use the fastest worker's time as a standard. Taylor believed that workers performed far below their capabilities unless forced to do so. The problem with this approach was that a worker would be bullied to get up to speed or be retrained or lose his job if he couldn't keep up. The usual result would be that productivity increased. This pleased management greatly, but in 1911, Taylorism had a setback. The workers at Watertown Federal Arsenal went on strike. The federal courts ruled that Time study was biased, inaccurate and unscientific and ruled it illegal on any governmet contracts. Taylor was a hard man, and was just as rigourous with himself. To train himself not sleep on his back, he thought it gave him bad dreams, he devised a harness with nails that would protrude to wake him in pain if he rolled over. Taylorism now means more disreet actions.

Contrary to Taylor, Lillian and Frank Gilbreths developed a way to visualize human motion through a photographic process called a stereo chronocyclegraph in order to increase efficiecy and productivity.. F Gilbreth was a building contractor and Lillian had her PhD in Psychology. Frank Gilbreth was obsessed with the speed and efficiency and built his firm by delivering finished building way ahead of schedule by analyzing tasks and designing new processes to speed the building process. He invented an improved scaffold to raise the worker as the buyilding progressed to maintain an optimum height for working. He devsied a packet system to hold bricks in uniform quantities and a fountain trowel for stringing mortar. When Lilliian got invloved, they turned this fascination into a management consultancy. Luckily, Frank was pro-union and they felt that management and workers were to share the burden of adopting thier system. Each worker, they felt, had a "right to happiness" and it was management's duty to eliminiate waste and fatigue from the job.
(Slides)
They replaced Taylor's stopwatch with a camera and would photograph workers doing tasks with small electric lights flashing twenty times a second attached to their wrists, and one cycle of a worker's movements were photographed in a darkened studio. The lights created pearl shaped exposures so that they could identify the dircetion the light was moving in and the grid p[laced in the background allowed them to measure distance. Irregulaties revealed changes in speed and hesitation. They then used those traces to build wire models. The cleanest, most compact and fluid model, was then analyzed as the standard process and taught to the other workers.

They were able to reduce a 115 step towel folding process to 16, but were fired from the job for accusing the client of not sharing in the new profit with his workers. The made 100's of Chronocyclographs, stacking boxes, packing pears, making buttons, transfering bactria cultures in laboratories, increasing typing speeds, laying tools out in the operating room.

Frank Gilbreth was also a peculiar fellow and he devised the right way to button his shirt and to lather up in the bath to save time, and he taught his children to do the same. They had 10 children, of Cheaper by the Dozen fame, and would have time charts of daily tasks that had to be timed and initialized by each child every day. The children were used to study ways to maximize household chores. The belief in ONE BEST WAY of doing was obsessive.
(MIKE MANDELL SLIDES)
...
One of the first problems of industrialization that came up was that workers were unable to see the contributions they had made to the final product and were condemmed to repetive tasks that quickly became mindnumbing. Worker dissatisfaction did affect production enough to warrant scientific investigation, so this has become the domain of industrial psychologists and sociologists, who study the behavior of people in organizational work settings. They observe worker motivation and morale, reward systems, training, communication processes and working conditions as factors which may affect productivity and worker satisfaction.

Two major contributions occured in this field: One by Hawthorne and the other by Maslow. The Hawthorwne Studies of assembly-line workers, begun in 1925, marked the first serious recognition of Human Relations as an important factor between people and organizations. Hawthorne also developed the Hawthorne Effect, Placebo Effect.

The other major influence in Psychology/Sociology was a man named Abraham Maslow, who's output spanned the 1940's-60's. After WW2, a Maslow first became known for his description of the "hierarchy of prepotency" in human motivations:
PHYSICAL NEEDS, SECURITY, SOCIAL ACCEPTANCE, LOVE, SELF-ACTUALIZATION
Observing that "man is a wanting animal" and that one desire is no sooner satisfied than another takes its place, he noted sense and order in the succession of motives. In the relatively rare individuals in whom all lower needs are satisfied a new motive can be observed, the drive for self-actualization--becoming everything that one is capable of becoming. (Interest in higher levels of motivation led Maslow to the study of self-actualized people, who differ from most people in being unusually healthy psychologically; having marked ability to free themselves from stereotypes; and perceiving everyday life realistically and accepting it without defensiveness. Self-actualizing people appear to have, or to have had, "peak experiences" of insight, joy, or intense awareness. In Toward a Psychology of Being (1962), Maslow described the characteristics of such experiences and the effects they have.)

Around WWI, several important human factors developments came into being, driven by military applications rather than industrial ones. Anthropometry, the study of human body measurements, often for comparitive purposes, was used to devise standardized clothing for soldiers. The access to such a huge number of men, basically allowed the military to gather anthropometric data for the first time for a large sample group. The skew of course was that the samples of the young healthy males skewed the results, and obviously women were hardly considered.

Another aspect came through WW1 for Industrial Psychology. In a study done over two years, 1,800,000 men were tested. Job specifications were written, job-knowledge tests invented, officer rating forms devised and training and psychological counseling programs were undertaken. Government job tests that are still in use got their start at this time.

The military basically took over the role of primary human factors source and client. Access to large numbers allowed it to test for biomechanics, namely the mechanical strength of humans. For example grip strength in a variety of position held ove a certain amount of time. (CSB)
(OVERHEADS)
Around WWII, Henry Dreyfuss Associates started to develop anthropometric guidelines for designers using data gathered from other sources, which are inherently biased since most are still culled from the military. The primary difference was that this data was being generated to allow designers to apply human factors information to design CONSUMER Products. (Before this data was systematically developed, designers used "rule-of-thumb"s like a table height should be @ 30", which worked fine for designing simpler objects, but not for complex objects like automobiles).

The charts generated focused on three different sets of numbers, called percentiles. Let's say the adult population make up 100%, researchers break down the group into 100 percentile groups with the firts percentile being the smallest and the 100th percentile being the largest. As designers, most of of the time, it suffises to limit ourseves to dealing with the 5th to the 95th percentile, meaning that we would cover 90 out of 100 adults. Dreyfuss charts include the 2.5%, 50%, and 97.5%, covering 95% of the the adults. Even better. Since the 1st and 100th percentiles are rare in that they encompass extremes, they are rarely considered. HD designed his charts to be visual aids, so that they could be photostated to scale and incorporated into drawings, but as designers, we really never consider the 50th percentile. because if I know that a small person (2.5 or 5 %) can reach the lever in front them, or see over the steering column, anyone in percentile groups above that can as well. Conversely, if a tall person (95 or 97.5%) can sit in car interior without hitting their head on the ceiling, anyone smaller can fit in as well. So what we look for are the extremes in relation to the tasks at hand.
In anthropometrics there is no such thing as a a 50th percentile pesron. You will never meet someone whose entire anthropometric measurements fits in just one percentile, and this is where reality and statistical purity collide, especially in product testing, once you have applied the numbers, so don't make assumptions every person who is 5'7 are going to have the same seated height.

 

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