Man has a history that is full of advances in the whole of human development. The systems of development is the most pronounced and prominent part of life. For instance, in the 21st century, there has been quite a lot of advances in technology which has continued up to date. These systems are meant to make the work of humans a bit easy. However, these systems require the efforts of man for them to be able to be effective. Man, therefore, is supposed to have a very sharp mind so as to be able to manipulate the systems and also be in a position to understand the way the systems operate. This, therefore, calls for training sessions as the systems keep on changing. The systems, on the other hand, are bound to cause accidents when they are mishandled. This leads to loss of lives as well as property. The interaction of the systems with the operators continues to change as the as the systems continue to evolve. The operators also have to seek more information and training on the same so as to be in a position to work with them appropriately. This paper entails a case study on human factors and will deal with the principles such as the visual sensory system, auditory and cognition. The paper will consist of relevant examples which will be related to each and every principle discussed.
Human factors are a set of influences on human thoughts processing that determines the decision reached when individuals are in ambiguous situations. Wickens et al (2004) argues that human factors can be visualized from the breakdown in communication between humans and systems which they work with. As a result, they consider certain specific goals that an analysis of human factors must accomplish in regard to this interaction. These include increasing safety, enhancing performance and increasing user satisfaction. Accordingly, they describe human factor as the study of the various factors and development of relevant tools that can create room to attain these goals. Human factor is thus generally applied to determine problems that occur between human and their interactions with various systems.
In this book the authors argues that in human factor studies various research methods may be employed. The underlying factor being the kind of research question that a human factor engineer needs to answer. They also distinguish between basic and applied studies. The former tends to create general theories that can be use to understand different systems. The latter, on the other hand, is more specific to a particular task, population, system or product. In this regard they concluded that applied research is relevant to human factor design because it derives principles that only apply to a particular setting. Therefore, human factor design may use both basic research methods like experiments and applied research methods like field studies. In this paper the aim is to use the case study to explain how various theories of human factors related to visual sensory system, auditory and cognition, can influence design of various systems.
- Visual Sensory System
Jim a traveler aged 50 years went to an unfamiliar city on a dark night and it was raining. As he was looking for his car in the parking lot, he could not differentiate them and ended up in a wrong car. After a thorough search, he was able to identify his. As he was driving, he made use of a guide map but did not clearly see the names of streets on the map. He gave up on using it. He pulls over and struggles to locate the wiper switch due to the rain. He cannot read the printed labels in the dark. He is later able to identify it and the wipers start functioning. Due to the traffic that was increasing behind him, he speeds up. He does not notice a road sign to his destination and therefore passes it. When he looks at the map for clarification and realizes the mistake, he tries to pull over but does not realize a pot hole and unfortunately lands on it.
The case study used by Wickens et al (2004) in this case is that of a traveler whose interaction with a car is impaired by environmental factors like the night, and rain, as well as poor system design and personal attributes. This section analysis in depth factors that need to be considered to develop an effective human system based on the visual sensitivity. According to Wickens et al (2004), night riding is a major challenge especially for the older people. They attribute this to the pronounced limitation of this population visual sensory system. Further, the challenge is claimed to have a direct correlation with two parts of the eye responsible for transmitting information to the brain, which are the eyeball and neural pathways. Besides, they also associate this limitation to brain processing and the perceptual process.
- Light as a Stimulus
The authors described particular stimuli that influence visual perceptions. These include light. Jim created visual perceptions with an electromagnetic energy that comprises of several key features. It is said that at any given moment human beings can only see a single point from a spectrum. This is characterized by a wave that has a particular wavelength and amplitude. The wavelength is the horizontal representation, while amplitude refers to the height. These two determines the hue and brightness of the stimulus respectively. They further explain that there is a minimum and a maximum level in the wavelengths of the stimulus. In addition, perceptual maps are also created from visual images of a mixture of more than one wavelength. The spectrum comprises of wavelengths of different colors. Some pure wavelengths like blue are diluted by mixture wavelengths. However, for wavelengths that are more saturated they are not diluted. As a result, in the case study the traveler’s eye was unable to discern the red sedan amidst a spectrum of different colors because the hue in this case red was not highly saturated.
Beside the hue the brightness is another factor that influences the visual perception formation in the mind of the traveler. Jim failed to see road signs on time, which eventually led to frustration and eventual breakdown of the car. Brightness is affected by intensity of light. In turn, this depends on the amount of light a particular object generates. In our case, the sun and the car headlights, considering it was in nightfall, then intensity was quite low. On the other hand, at the point Jim veered outside the road he was driving with dim light thus lowering the intensity. Besides, the object the traveler needed to see in this case the road sign illuminance was poor because they were black. Illuminace refers to the amount of energy striking an object in order to be seen. The distance of an object from the light source determines its illuminance. The object so struck also needs to have high illuminance to make it more visible. In this case, luminance refers to light an object absorbs or reflect. Therefore, object brightness can be the same because of the difference in either illuminance or luminance. In the case of Jim the traveler we can say that the brightness was poor because of the poor illuminace as the source of light was dim giving the traveler hard time and the luminance from the black road sign was poor.
- The Visual Receptor System
If we consider the case of Jim the traveler, the light getting into his eye through the eyeball is then changed into electromagnetic neural energy. The eyeball has certain biological characteristics that affect light penetrating through it, causing some distortions which make it difficult for him to see under certain environments. This section thus highlights the argument on what human factors to consider in addressing this aspect in driving.
One such characteristic is the behavior of the eye as the lens. The eye consists of several parts like the cornea, which absorbs the light getting in and this increases as one gets older. It also has the pupil that either opens in darkness or closes in brightness to regulate flow of light in different illumination levels. One aspect of the eye that can affect the interaction of human and the systems around them is the accommodation factor. This entails adjustment of eye lens so as to focus the images of certain objects on the retina. This adjustment is controlled by the ciliary muscles. The ciliary muscle contains sensory receptors responsible for sending signals to the brain. Objects of different shapes and at different distances from the eye form different types of shapes. This accommodation takes times and certain factors also can affect the shapes formed and thus lead to the wrong conclusions about the objects observed. Jim was not able to identify a post showing the direction where he was heading to.This includes myopia, which is a state known as nearsightedness which is a failure of the muscles to create a flatter shape of an object that is far away, therefore, making it difficult to bring it into focus. The opposite is also true especially at older age when people fail to focus objects that are close. In consideration of the visual receptor system we can argue that Jim who was travelling failed to accommodate road signs probably because he was driving at a high speed in an unfamiliar road denying his lens time to accommodate the objects. There was no evidence of him being either nearsighted or farsighted to warrant an argument for associating this failure to notice road sign to them, but the speed could be a better explanation.
Jim was not able to identify his vehicle from the parking lot. This is explained by the other anatomical factors of the eyes that affects visual perceptions relates to cones and rods. When an object is focused on the retina it falls on different part. The eye has two different cells used as the visual receptors responsible for transforming the light laminated by an object to electrical impulses of the neural energy that is sent to the brain through the optic nerve. These cells are known as the cones and rods. Each of them poses different characteristics all of which have different effect on the visual sensory processing. One such location in the retina inhibited only by cones is the fovea. In the immediate surroundings of the fovea there is a mixture of cones and rods, but the latter declines as one move out. The cones enable high resolve or have greater ability to focus object with high acuity. However, human are able to see things in motion more easily if the object falls within the periphery. The rods are good with sensitivity and capable of detecting objects in dim illumination. Nevertheless, the rods have poor color sensitivity and as a result, not able to distinguish different lights wavelengths. Since, the driver in the case was only using the rods cells as visual receptor this explains the failure to pick the red sedan car in the parking lot from the rest. Again they also have another challenge known as adaptation. This refers to their tendency to lose their sensitivity when subjected to long period of light. This might explain why the driver veered outside the road after turning the dome light to look at the map.
- Sensory Processing Limitations
Jim on his way was unable to identify a pothole as he was speeding. Wickens et al (2004) explores the role played by visual contrast sensitivity in inhibiting right decision based on the visual perception. They explain contrast sensitivity as the failure to discern a darker area from the lighter one. They explain that this is a very important attribute because it can pin point certain conditions like the pot hole that traveler failed to notice while driving in the case. Since this is expressed as a reciprocal of lighter area compared to the darker one, the high the value the lesser ability to detect the contrast.
Beside the illumination factor previously mentioned as an inhibitive factor in detecting different hues and thus contributing to the traveler difficulty in picking the red sedan car. Color sensitivity is another human factor engineers need to take into consideration. According to Wickens et al (2004) many male are unable to detect certain hues or colors like red from green. As a result, color is really used as the main way of communicating traffic information. Because of both poor contrast sensitivity and color vision certain populations especially the old ones have problems driving at night and more so in areas strange to them. Lastly, there is also glare, which is sudden but unnecessary light with high intensity. For instance, just before the traveler veered off the rear a glance at the rear mirror had this type of mirror. The effect was to cause both distraction and annoyance. It affects the rod sensitivity a cell that we earlier learnt is important when driving at night or in less illuminated environment. The glare is therefore, also an important human factor that can affect visual processing.
- Bottom-up and top-down Processing
Jim had a problem in driving at night and especially now that he was in an unfamiliar road. The bottom-up refers to human factors already considered, which determines the quality of information reaching the brain to develop perceptions. In this case, accommodation process that relates to contraction and expansion of the ciliary muscle to let the image focus on the retina can affect the quality of information. The aged would not be able to open their muscles properly at night making it difficult for them to accommodate appropriate information just in time to drive in unfamiliar environment. Beside accommodation, two more cues enable human to make judgment on the distance of an objects in space. These include convergence that enables the muscle to adjust and place an object in the right retina position. The other cue is binocular disparity, which enables the brain to determine how far away an object is. The three cues though are only important for estimating the distance and the speed of only those objects that are some few meters from the observer.
Accordingly, human beings depend on the top-down processing cues like the pictorial cues to determine the distance and depth of objects that are in long distance. These cues are subject to experiences that one has. Some of the important cues for determining depth include linear perspective that shows straight lines converging towards the distant objects. There is also interposition, which means objects that are close tend to blur those that are at a distance. On the other hand, human beings are able to tell their positions while in motion due to relative motion, which is the tendency to adjust the head back and forward to determine the relative distance of objects. As the object comes nearer its size becomes bigger and vice verse. As long as the human beings are using these cues, they enable them to determine accurately motion and space perception. Nevertheless, some factors like darkness can distort depth perception, which was the case for the night traveler.
- Visual Search and Detection
In the case study, the driver was unable to identify several things including the Route 60 road sign. The expectancy theory can be used to explain why the driver failed to detect the road sign on time. According to Wickens et al (2004) this was due to his use of previous knowledge that convinced him that there was no chance that the road sign would be to the left of the highway. This made him to miss switching the lanes on time.
Joseph is a driver of a bus on a busy route in one of the towns in the city. He is becoming frustrated as a result of the noise that the bus produced in the engine. The noise was stressful and unpleasant and this made him go home with the ears ringing and a fierce headache. He was very much concerned because he could not hear the door bell when the passengers reached their various destinations. This made the customers very angry as the driver sometimes did not drop them at their destinations. Most of the passengers used to comment that they will not use the vehicle again as they felt frustrated. Some times the driver was not able to concentrate on the road because of the disturbance brought about by the noise. The problem was that the owner of the bus did not want to use money to repair the bus. The driver was happy when one day a traffic police ordered that the bus be repaired before carrying passengers on that route.
Stimulus that is involved in the process of hearing is sound. This is the vibration of air molecules. There are three main types of sound. These are the important communication brought about by speech like the passengers shouting stop for the driver to drop them, the alarm critical tone like the door bell in the bus and the undesired noise that is in the places of work as mentioned above. It is important to understand the way the ear functions in the process of hearing. The ear has the pinna that is involved in collecting sound. Due to the shape that it has (asymmetrical), it offers information on the source of sound. The outer and middle ear which consist of eardrum, anvil, hammer and stirrup bones are involved in conducting and amplifying sound waves into the inner ear. The middle ear has muscles that respond to noise so as to attenuate the vibration amplitude before reaching the inner ear. Inner ear has cochlea where the basilar membrane is found. This is involved with sound energy physical movement. This is converted to electrical energy in the nerves and then passed to the brain through the auditory nerves. The transduction is made possible by displacement of small hair cells on the basilar membrane that moves opposite of sounds with different frequency.
Noise is a factor that disrupts the transmission of a message. When Joseph is on the road, he is worried about the noise coming from the engine as it is hazardous. This is because one is not able to concentrate on the road especially when another car hoots; the noise distracts making the driver not to hear the hooting vehicle. Noise is also a stressor. It can degrade the performance of the driver. One of the effects of noise is the temporary threshold. The driver used to say that whenever he stepped out of the noisy bus and moves to a quiet place, he could still have problems in hearing properly because of an effect of the exposure to noise usually referred to as carry over. The TTS (temporary threshold shift) is quite large immediately after the termination of the noise. It then reduces after a few minutes when the hearing is recovered. TTS can be said to be the amount of hearing loss which is present few minutes after termination of the source of the noise.
Joseph also had a problem because whenever he was caught up by traffic jam, he always suffered because of the noise emanating from the other vehicles as well as from industries around the area. The form of noise which has a lot of implications to the drivers is PTS (permanent threshold shift). This defines the occupational deafness which comes up after the driver is exposed to many months or years of very high noise intensity. PTS is great with longer and louder exposure to any noise. It is important however to note that in certain circumstances, noise may be important. For example, low noise like soft music, humming of the fan may mask the disruptive noise in the environment. This made Joseph to sometimes switch on the radio and put on the earphones so as to listen to soft music.
The vestibular senses are very important in human system especially when interacting with the systems. They play important roles that are related to motion sickness and illusions. These illusions and motions occur for example when the vehicle for example is tinted or it is very dark such that the driver and passengers cannot be able to see whatever is outside. This may lead to the driver losing control as a result of rolling and swaying on the road. This could even lead to the driver causing an accident.
John had an interview to attend and was late. The city he was travelling to was quite new to him. The instructions he was using were very confusing. He tried to make use of display mode that used voice so as not to lose concentration on the road. Traffic increased at a high rate. He went on to activate the voice display without pulling over. Even with the efforts applied, he was lost. He got his phone to enquire the direction from a friend but unfortunately dialed the wrong number. He was frustrated by the fact that he did not get help. He did not see a vehicle overtaking as he was busy on the phone and decided to stop the vehicle. He pressed on the brakes hard and pulled over to relax and compose himself.
The mind is able to process more and more information from the environment. The information is meant to make individuals achieve goals so as to be successful in life. John had to deal with many issues which were on his mind. He was late for an interview, he really wanted to pass the interview and start a new life, here is the challenge on the road, he cannot get help and other problems. The system of human beings that is involved in the processing of information has various stages of transforming the information. These stages are the perception one has on the environment, transforming the information and the way to respond to the information. Perception may sometimes lead to execution and selection of a certain response. For example, when John makes effort and swerves so as to avoid collision with a converging vehicle. Sometimes, this action could be delayed, or even it may fail to happen at all. This happens as the person tries to manipulate or think about the perceived information in the so called working memory (Cowan, 2001). An activity where working memory can be used in creating a permanent representation of the said information is long term memory (Wickens et al, 2004). This kind of memory can be retrieved even after hours, days, months and years later.
Drivers are supposed to make use of selective attention. One of the major causes of accidents is failure to pay attention to driving itself. Drivers are prone to answering calls even when driving. John wanted to make a call as he was driving. He even dials the number but unfortunately dials the wrong number. This makes him be unable to see a vehicle that was speeding to overtake and almost causes an accident. The way to select to channels to attend to is achieved as a result of; salience, expectancy, value and effort (Wickens et al, 2003) These are represented in a similar frame work of contrasting stimulus driven process that is bottom up and knowledge driven top down process. All these characterize the so called attention capture. For example a car horn captures the attention of an individual. The dimensions of Salient stimulus have been identified by to alert the events that are important through the alerts and alarms. However, selective attention is sometimes inhibited. This is because people prefer scanning short distances instead of long ones. This is the reason as to why fatigued drivers who don’t have a lot of effort to offer do not look behind to see a blind spot when they are changing lines. The very direct consequence in selective attention is perception. This involves extracting visual meaning or auditory meaning that is processed by senses. A driver may for example look on the roadside and perceive a hazard of a nearing vehicle.
There are two types of memory. These are the long term and short term. Some times people experience memory failure for example John had forgotten a phone number of a friend who is so close and whose number he had dialed few hours earlier. Working memory is sometimes called the short term memory. It involves holding little information that can be rehearsed. John was unable to recall the phone number of his friend even though he had dialed it the same morning as he was travelling. Some of the factors of working memory limits are; reducing the load of working memory, keeping the letters and numbers separately, offering visual echoes, exploiting chunking, and providing placeholders when it comes to sequential tasks.
Human factors are a field that is growing at a faster rate. In small industries people have been assigned certain responsibilities such as engineers even without training in the field. It therefore calls for research so as to come up with materials to be provided to schools, colleges and in workplace so that people can use them as references to help them understand the human factors
We have seen that Human factors are a set of influences on thoughts of human processing which are involved in determining the decision reached when individuals are in ambiguous situations. These human factors can be visualized from the breakdown in communication between humans and systems which they work with. In that respect, human factor design may use both basic research methods like experiments as well as applied research methods like field studies. In this paper the main objective of using the case study to explain how various theories of human factors related to visual sensory system, cognition and auditory influence the design of various systems has been achieved.
Cowan, N. ( 2001). The magical number 4 in short-term memory: a reconsideration of mental storage capacity.Psychological science. University of Missouri, Columbia.
Wickens, C. D., Lee, J., Liu, Y., and Becker, S. G. (2004). An Introduction to Human Factors Engineering, (Ed. 2). Upper Saddle River, NJ: Pearson Education International.
Wickens,D, Juliana G, John H, William J, Donald A (2003). Human Factors: The Journal of the Human Factors and Ergonomics Society.45:360
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