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Although most older people live active and relatively healthy lives, increased age is associated with changes in certain abilities, such as vision, hearing, and memory, that make it difficult for some older people to perform tasks such as driving, using equipment such as computers, or remembering to take medications. Furthermore, older people are more likely to suffer from some type of chronic disease such as arthritis, high blood pressure, or dementia. People with these conditions often require assistance with basic activities such as preparing meals, bathing, or finding their way. Aging is also associated with positive changes, such as increased wisdom, knowledge, and experience, and thus older people represent an extremely valuable resource to the community, the workplace, and the family. There are numerous examples, such as senior mentoring, of how older adults continue to make productive contributions to society.

The challenge confronting researchers, designers, and policy makers is to develop strategies to maximize the ability of older people to reach their potential and remain healthy and productive. In addition, strategies are needed to help older people who are frail or disabled receive needed care and support. Human factors engineering, the multidisciplinary science that focuses on user-centered design, can make valuable contributions toward accommodating an aging population and enhancing the lives of older adults. Relevant applications of human factors include: housing design, transportation, equipment and product design, and work

Human factors engineering

Human factors engineering is the study of human beings and their interactions with products, environments, and equipment in the performance of tasks and activities. The field of human factors is interdisciplinary, encompassing the disciplines of engineering, psychology, computer science, physiology, and biomechanics. The focus of human factors research is the study of human capabilities, limitations, and characteristics in relation to real world activities and systems. Relevant research projects might include understanding the implications of age-related changes in vision for the design of visual displays or how age-related changes in memory impact the ability of seniors to learn to use new technologies.

The objectives of humans factors are to improve the fit between people and the designed environment so that performance, safety, comfort, and user satisfaction are maximized. To achieve these goals, human factors engineering uses a systems approach to design, where the capabilities and limitations of the user are evaluated relative to the demands generated by products and tasks. An example of this approach would be evaluating the force requirements necessary to operate a hand control, such as door knob, relative to the grasping and strength capabilities of the intended user population.

The focus on user-centered design makes human factors engineering a natural discipline to address the problems of older adults and help them retain and enjoy independence in their later years. Using the techniques and methods of human factors it is possible to understand the impact of age-related changes in abilities on the performance of everyday tasks and activities, identify areas where problems and difficulties arise, and discover solutions to address them. These solutions might include redesign of equipment or environments, interface design solutions, training solutions, or suggestions for the development of new products or technologies.

Areas in which human factors engineering can be used to improve the lives of older people include: mobility/transportation, living environments, and information technology (for a discussion of health care applications see Czaja, 2000).

Mobility and transportation

It is fairly well known that many older people, because of difficulty walking, using stairs, driving, or using public transportation, have difficulty getting from place to place. Problems with mobility often make it difficult for older people to get to stores, banks, and physicians' offices; to participate in community activities; or to maintain contact with family and friends. These problems are exacerbated for older adults who live in suburban or rural communities where public transportation is often minimal or nonexistent and driving is the only option. Driving is problematic for many older adults, making this a topic of great interest to policy makers, researchers, and the elderly themselves.

In this regard, issues related to the safety and mobility of older drivers has received considerable attention within the human factors community. This research has been directed toward understanding the difficulties experienced by older drivers and the reasons for these difficulties, as well as identifying potential design solutions. Several researchers have found that problems with driving are related to deficits in vision and aspects of cognition (see Ball and Owsley, 1991). It is also known that certain tasks, such as left-hand turns, or certain environments, such as driving in construction zones, are difficult for older people. Many older people also report difficulty adjusting to changes in automobile design.

Proven areas of effective intervention include redesign of roadway signs and warnings, modifications in the design of the automobile, and training. It has been shown, for example, that providing older people with training on abilities important to driving, such as visual attention, offers the potential of improving driving performance. Strategies such as increasing the contrast of roadway signs so that they are easier to read or providing drivers with additional signs about upcoming traffic or roadway demands can also help enhance the safety of older drivers.

Other important areas of human factors intervention include identifying alternative solutions, such as modifications in public transportation systems to make them more easily available, so that the need for driving is reduced. Older people commonly report problems using buses or subways due to inefficient design. Common problems include difficulty getting on and off, crowding, lack of security, and lack of availability of transportation systems. Other problems relate to understanding schedules and maps. Many of these problems are amenable to human factors solutions.

Living environments

Another area where human factors engineers can make important contributions is the design of living environments. Contrary to popular belief, most older people live in the community, either alone or with a relative. Many older people also spend a great deal of time at home. However, living at home is often challenging for older adults, as they find it difficult to perform tasks such as bathing, cooking, and cleaning. The rate of home accidents is high among older people. Problems with home activities and home safety are often linked to inappropriate housing design.

Falls among elderly people are common, and in fact represent a frequent cause of accidental injury and death. Furthermore, many older people restrict their activities because of fear of falling. Reasons for falls among the elderly include losses in vision, balance, and reaction time, and changes in gait. Common locations or sources of falls include stairs and steps; bathtubs and showers; ladders and stools; and tripping or slipping on throw rugs, runners, or carpets. Understanding the reasons for these falls will help uncover design solutions. Many falls on stairways occur because older people, due to declines in vision, fail to perceive the first or last step. This problem might be addressed by installation of more lighting in stairways and highlighting, through the use of color, the beginning and ending of steps. Handrails can also help remedy the problem. A more radical solution is to design housing without stairs, or to design in a way that minimizes the need for people to go up and down stairs. Strength and balance training has also been shown to reduce the risk of falls among the elderly and to reduce the consequences if a fall should occur. In all of these examples, the goal is to help insure a match between the capabilities of the older person and the demands of the task and the environment.

Computer technology and information systems

Computer and information technologies offer the potential of enhancing the independence and improving the quality of life of older people. These technologies make it possible to bank and shop at home, maintain contact with family and friends, access physicians and health care providers, access information about community resources, and participate in educational programs. Despite popular stereotypes, older people are interested and willing to use new technologies. However, because of lack of familiarity with technology, lack of training, and difficult-to-use systems, technology is often a source of frustration for many older adults and the potential benefits of technology for this population are not realized. This is another area where human factors engineers can, and do, make significant contributions.

An excellent example relates to automatic teller machines (ATMs). A recent survey showed that older people use ATMs far less frequently than younger people because they don't feel safe using them, don't feel they need them, or do not know how to use them. They also indicated that they would be more likely to use ATMs if someone showed them how to use them. Researchers at Georgia Institute of Technology have discovered effective ways of teaching older people to use ATMs. Specifically they found providing older adults with an on-line tutorial that provided hands-on interactive experience with an ATM system and practice on actual ATM tasks improved their ability to perform ATM transactions. They also discovered that simple changes in system design, such as improving the visual display and the content of on-screen messages, greatly enhance the ability of older people to successfully use ATMs. It is also important to understand that these types of design changes are usually effective for people of all ages.

Several researchers (e.g., Charness, 2000; Walker, Philbin, and Fisk, 1997; Smith, Sharit, and Czaja, 1999) have shown that current input devices, such as the computer mouse, also make it difficult for older adults to use technology. These problems are related to age changes in movement control. Tasks such as double-clicking or cursor positioning are particularly difficult for older people. Some of these difficulties can be eliminated by making the interface easier by changing the gain and acceleration of the mouse, or by switching to alternative input devices such as a light pen. Current findings also suggest that voice control may be beneficial for older people, as it minimizes the need for use of the hands and fingers.

Software that is complex also causes problems for older people. For example, many older people are interested in learning to use the World Wide Web (WWW), but find it difficult because of poor interface design. Strategies such as changing the structure of the network and menu characteristics so it is easier for people to find information have been found to be effective for both younger and older people. Other techniques, such as providing on-screen information regarding search history ("where one is and where one has been") also aid performance, as the demands on memory are reduced.

The topic of aging and information technology is becoming increasingly important, as the use of technology is permeating most aspects of society. The challenge for human factors engineers is to help insure that technology is useful to, and useable by, older adults. Much needs to be done in the area of training and interface design in order to meet this challenge.


Human factors engineering can be used to help design tasks, products, equipment, and environments to help accommodate an aging population. Research in this area has demonstrated the importance of attending to the needs of older people in system design, and also that training and design solutions can be beneficial for older people. The basic premise of human factors is that successful performance results from user-centered design and a fundamental understanding of user capabilities, needs, and preferences. Improving the health and quality of life of older people requires that knowledge of aging be applied to the design of products and environments.

Sara Czaja Chin Chin Lee

See also Balance and Mobility; Driving Ability; Functional Ability; Hearing; Home Adaptation and Equipment; Housing and Technology; Intellegince; Memory; Technology; Vision and Perception.


Ball, K., and Owsley, C. "Identifying Correlates of Accident Involvement for the Older Driver." Human Factors 33 (1991): 583595.

Charness, N. "Aging and Communication: Human Factors Issues." In Aging and Communication: Opportunities and Challenges of Technology. Edited by N. Charness, D. C. Park, and B. A. Sabel. New York: Springer, 2000.

Czaja, S. J. Human Factors Research for an Aging Population. Washington, D.C.: National Academy of Science Press, 1990.

Czaja. S. J. "Ergonomics and Older Health Care for Older Adults." In The Encyclopedia of Care of Elderly. Edited by M. D. Mezey. New York: Springer, 2000.

Czaja, S. J., and Sharit, J. "Age Differences in Attitudes Towards Computers: The Influence of Task Characteristics." The Journals of Gerontology: Psychological Sciences and Social Sciences 53B (1998): 329340.

Fisk, A. D. "Human Factors and the Older Adult." The Magazine of Human Factors Applications 7, no. 1 (1999): 813.

Kalasky, M. A.; Czaja, S. J.; Sharit, J.; and Nair, S. N. "Is Speech Technology Robust for Older Populations?" Proceedings of the 43rd Annual Meeting of the Human Factors and Ergonomics Society. (1999).

Lambert, L. D., and Fleury, M. "Age, Cognitive Style, and Traffic Signs." Perceptual and Motor Skills 78 (1994): 611624.

Lawton, P. "Aging and the Performance of Home Tasks." Human Factors 32 (1990): 527536.

Rogers, W. A.; Fisk, A. D.; Mead, S.; Walker, N.; and Cabrera, E. F. "Training Older Adults to Use Automatic Teller Machines." Human Factors 38 (1996): 425433.

Rogers, W. A.; Meyer, B.; Walker, N.; and Fisk, A. D. "Functional Limitations to Daily Living Tasks in the Aged: A Focus Group Analysis." Human Factors 40 (1998): 111125.

Smith, M. W.; Czaja, S. J.; and Sharit, J. "Aging, Motor Control, and the Performance of Computer Mouse Task." Human Factors 41 (1999): 389397.

Staplin, L., and Fisk, A. D. "A Cognitive Engineering Approach to Improve Signalized Left-Turn Intersections." Human Factors 33 (1991): 559571.

U.S. Department of Transportation. Traffic Safety Facts. Washington, D.C.: National Center for Statistics and Analysis, 1994.

Walker, N.; Philbin, D. A.; and Fisk, A. D. "Age-Related Differences in Movement Control: Adjusting Submovement Structure to Optimize Performance." Journal of Gerontology: Psychological Sciences 52B (1997): P40P52.


See High blood pressure

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Human Factors: User Interfaces

Human Factors: User Interfaces

Every computer system has an interface that consists of software and hardware, which are needed for users interacting with the system. User interfaces allow people to input commands to the computer, read the computer's output, structure information, and complete certain tasks that may be related to business, education, government, medical, military, industrial, scientific, or home environments. Different types of interfaces allow users to perform a multitude of tasks on a computer, such as creating documents, searching the Internet, or sending and receiving e-mail messages. A user interface may enable a user to enter, locate, manipulate, analyze, monitor, or retrieve information.

Effective user interfaces are extremely important. Many users find computer interfaces difficult to use, and a user's ability to perform tasks on a computer is directly related to the effectiveness of the computer interface. Human-computer interactions should be structured and presented to ease learning, minimize errors, and facilitate use. A poorly designed interface display may lead to user mistakes, non-use of the computer system, and low user satisfaction. In general, interface design needs to answer questions about when, what, and how a user completes a task. User interface designers consider issues such as human memory, color perception, and task complexity to define the display requirements for a computer interface.

Computer games, such as Nintendo and Red Alert, are very popular with people of all ages. Popular computer games include sophisticated interfaces using multimedia effects such as color and sound. Many schools use software programs in the classroom to teach skills and make lessons more interesting for students. The importance of a well-designed user interface is more important than ever as the number of people using computer systems has dramatically increased over the last decade, fueled by the dramatic increase of the Internet on home computers.

Types of Displays

Humans interact with different computer interface displays, such as command line interfaces, menus, natural language, form-fill and spreadsheets, WIMP (windows, icons, menus, and pointers) interfaces, and three-dimensional interfaces. Displays vary in format, type, size, color, and content. Users find color displays attractive, which makes computer software easier to use.

Command line interfaces allow users to give instructions to the computer using commands and keywords. Most online search engines use command line interfaces. Menu-driven interfaces provide the user with a set of options from which to choose. For example, an automated teller machine (ATM) displays a list of options that allow users to deposit and withdraw money and check account balances. Natural language interfaces allow users to communicate with the computer through spoken or written sentences. For example, the Internet search engine "Ask Jeeves" allows users to ask questions when searching for information.

Fill-in forms or spreadsheets present users with a form to complete with numbers or words. For example, to book an airline ticket via the Travelocity web site, a user must complete a form by providing destination and travel details. WIMP interfaces combine various display types and allow users to complete multiple tasks at the same time, click on icons (or pictures), and use their mouse as a pointer. For example, Microsoft Windows allows users to use many software programs at the same time.

Three-dimensional (3D) interfaces are used in virtual reality (VR) . For example, computer games often use 3D interfaces and helmet-mounted displays. As the power of personal computer systems increases, the use of 3D interfaces becomes more practical. New types of heads-up displays can project information or images on the windscreen of a car or airplane.

Agents, Direct Manipulation

Computer interfaces may include software agents that perform tasks for users. Agents may perform tasks directly specified by a user, or watch and learn from a user's actions and perform tasks without the user present. For example, an e-mail agent may filter a user's e-mail. Direct manipulation means that specific tasks are represented as pictures to make the task easier for the interface user. For example, to print a document in the word processing package Word, the user can click on a printer graphic to initiate printing.


Software is the sequence of instructions in one or more programming languages or software tools that enable a computer application to automate a task. Computing languages, such as C++ or Java, are used by software engineers to create different types of interfaces with different features, depending on the task for which the interface was designed. Each software program provides users with an interface that allows them to complete a particular task or set of tasks. For example, a word processing interface that allows users to create and modify documents has different features than a web search engine interface. Better software design and software tutorials can make computer interfaces easier to use.


Hardware refers to the type of computer used to interact with a software program such as a micro or personal computer. Computer hardware includes the keyboard, mouse, joysticks, and other devices that allow the user to interact with the computer system. New technologies such as speech input, touch screens, and 3D displays increase interface usability. Computers are also getting smaller and more powerful. Portable wireless computers allow users to access the Internet from any location at anytime.

The hardware used in any given system has a significant impact on the user interface that can be designed. For example, the limited screen resolution and processing power available on a wireless telephone limits its ability to perform the intensive 3D graphics that are available on a typical home computer. Improved computer hardware and software can allow users to complete tasks more quickly and effectively, reduce user errors, and minimize the training time and skill needed to use a computer. Specially designed user interfaces are helping younger, blind, elderly, and disabled people use computers. Better interface designs can continue to reduce the potential health risks of prolonged computer use. The interfaces of the future will take users into a 3-dimensional world of virtual reality sight, sound, smell, and touch.

see also Assistive Computer Technology for Persons with Disabilities; Ergonomics; Graphic Devices; Interactive Systems.

Amanda Spink


Dix, Alan, Janet Findlay, Gregory Abowd, and Russell Beale. Human-Computer Interaction, 2nd ed. London: Prentice Hall, 1997.

Neilsen, Jakob. Designing Web Usability. Indianapolis: New Riders Publishing, 2000.

Shneiderman, Ben. Designing the User Interface: Strategies for Effective Human-Computer Interaction. Reading, MA: Addison Wesley Longman, 1998.

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Human Factors

Human factors engineering, a term that is often used synonymously with the word "ergonomics," is the science and design activity that deals with improving how people interact with their environments, tools, and tasks as part of a system; the objective is to make these interactions safe, productive, and comfortable. Or, perhaps better stated from an engineering perspective, human factors engineering is the science and art of designing the environment, tools, and tasks so they interact well with humans as part of a system.

This discipline is difficult to implement in workplaces and homes on Earth. Many problems are technically complicated, as issues of money and scheduling are usually constraints, and the traditionally successful ways of getting things done make the politics of improvement and innovation complex. Allocating tasks along the continuum from manual to machine; taking into account all of the capabilities and the limitations of people (as individuals or teams) and machines; accounting for the dimensions of power, tools, feedback, control, automation, memory, computation, analysis, decision making, and artificial intelligence; and bringing together the sciences and practices of engineering, psychology, biology, communications, and economics are issues that human factors engineers deal with every day.

Stepping off the home planet to the reduced gravity and relative hostility of space adds considerably to the problems addressed by space human factors engineers, but the discipline is the same. The environment in space is different in regard to factors that go beyond the effects of gravity (no ground reactive support; the need to wear protective yet cumbersome suits); the human body adapts to these changes in different ways over time, and the work that must be done is often specific to space in terms of what has to be done or how it can be done.

Meeting the Challenges of the Space Environment

Microgravity has a direct and immediate effect on the human body. Each cell reacts individually to microgravity, and the body as a whole immediately undergoes changes in chemistry and dimensions. Fluids shift to the upper body, and compression no longer acts on the spine and the soles of the feet. Calcium is lost from the bones, and muscles atrophy from lack of use, resulting in diminished strength. A human arm floats up rather than hanging down by the hip. The design of workstations and computers must take into account these differences in stature, posture, biomechanics, and strength. For example, gravity will not keep a computer mouse on the table-top, and so a different tool must be used to move the cursor. A touch screen was studied, but it was very difficult for a person in space to hold the arm out and maintain contact with the screen without pushing oneself away. Voice control of the computer holds promise, but crewmembers want something much more reliable on the machine side and much more forgiving of human error. The current compromise is a trackball-type device or a joystick. But what if the crewmember floats over to the workstation upside down? How should displays and controls be designed so that procedures are not performed backward?

In orbit, feet are nearly useless appendages after an initial kickoff and moving around is controlled mostly by using handrails. Pushing on a toggle switch is more likely to result in rotating the operator's human body than in repositioning the switch unless the operator is restrained. Mobility aids and force restraints are essential in reducing bruises among people moving and stopping in space. In partial gravity environments, such as on Mars or lunar surfaces, moving from one place to another is very different from the same activities on Earth. Video sequences of humans on the Moon show that they sort of bounce around. Studies in simulated Mars gravity conducted in parabolic flights of National Aeronautics and Space Administration (NASA) research airplanes have demonstrated that a different way of moving comes naturally to the human explorer. Space suits and tools will have to be designed to take into account the way human behavior changes in space.

Natural convection currents do not act without a gravity field, and so hot air does not rise. If an astronaut wants to breathe fresh oxygen in every breath, there have to be fans to circulate the air. The heat from an electrical component such as a laptop does not move away with the air, and so energy must be used for active cooling of every item that dissipates heat, including the human.

Working in a pressurized space suit is difficult, especially for the hands. Controlling telerobots or programming automated machines leaves little room for error, takes a lot of time, and requires special skills. The confined cabin of a spacecraft limits the range and exercise of human senses and perceptions. The isolation from colleagues, family, and friends can alter social relationships, expectations, and support structures. The hostility of the external space environment and the inherent risk of spaceflight add stress to everyday tasks. A mistake or inattention can quickly result in death or mission failure and consequently everything becomes much more important.

The nature of space combined with the new human-designed environments and tools for living and working in space impact the ways in which people do things. Solving cognitive problems; meeting unexpected challenges; maintaining safety; staying attentive and motivated on long, boring flights from planet to planet; and maintaining teamwork, family ties, and a healthy personality are all aspects of the interaction between a human and the designed environment.

see also Communities in Space (volume 4); International Space Station (volumes 1 and 3); Living in Space (volume 3); Living on Other Worlds (volume 3).

Theodore T. Foley II and Sudhakar Rajulu


National Aeronautics and Space Administration. Man-Systems Integration Standards, NASA STD-3000, Revision B. Houston: Johnson Space Center, 1995.

Salvendy, Gavriel, ed. Handbook of Human Factors. New York: Wiley, 1987.

. Handbook of Human Factors and Ergonomics, 2d ed. New York: Wiley, 1997.