Copyright 2006 John Wiley & Sons, Inc Chapter 4 – Physical Engineering HCI: Developing Effective Organizational Systems Dov Te’eni Jane Carey Ping Zhang

Copyright 2006 John Wiley & Sons, Inc Learning Objectives  Define physical engineering.  Understand and discuss human performance.  Understand and discuss human limitations.  Understand and discuss human perception through the various sensors including: Vision Audition Touch  Explain Fitts’ law and how it pertains to HCI understanding and physical engineering.

Copyright 2006 John Wiley & Sons, Inc Introduction  Ergonomics has been at the heart of human factors engineering. The word was coined in 1949 from two Greek words, ergos, which means work, and nomos, which means natural laws.  It has come to mean "the fit between man and machine". The group that coined the word, ergonomics, was interdisciplinary and included psychologists, design engineers, work study engineers, industrial medical officers, and others with an interest in human performance.

Copyright 2006 John Wiley & Sons, Inc Introduction  Ergonomics: the physical fit between human and machine.  Ergonomic Engineering: the science of human engineering which combines the study of human body mechanics and physical limitations with industrial psychology.

Copyright 2006 John Wiley & Sons, Inc Human Performance and Limitations Ergonomic engineering is concerned with the physical interfaces between the human user and the computer and has three main categories: analysis, design, and assessment (Bullinger, 1988). The analysis category focuses on human attributes and capabilities, the tasks to be performed, and the technology that is being used to aid in task performance. The performance-related goals of ergonomics are to improve: The human ability to handle physical load or demands of the work situation, Performance (reduce errors, improve quality, reduce time required to complete task), and End user acceptance of the system.

Copyright 2006 John Wiley & Sons, Inc Human Performance and Limitations Human Performance: measured by reducing errors, improving quality, and reducing time required to complete task. Figure 4.1: The expanded Fit between human, task and computer in the work context context that this happens in is important.

Copyright 2006 John Wiley & Sons, Inc Human Limitations Human Limitations: human limitations which are physical in nature and include such aspects as levels of hearing, arm reach, muscular strength, visual distance and others. Sensory Limits  Human sight, hearing, smell, touch, and taste have thresholds and deficiencies.

Copyright 2006 John Wiley & Sons, Inc Human Limitations Responder (motor) limits:  Humans have limited reach and strength.  Keyboard layout designs and required mouse actions often cause users to change body positions in order to execute them.  Often resulting in health problems.

Copyright 2006 John Wiley & Sons, Inc Fitt’s Law  Fitts’ Law: measures the time it takes for a human to move a certain distance. Fitts’ Law provides much of the theory underpinning our understanding of human performance and limitations. Fitts' law is a robust model of human psychomotor behavior developed in The model is based on time and distance. It enables the prediction of human movement and human motion based on rapid, aimed movement, not drawing or writing.

Copyright 2006 John Wiley & Sons, Inc Fitt’s Law  Mathematically, Fitts' law is stated as follows: MT = a + b log2(2A/W) Where  MT = movement time  a,b = regression coefficients  A = distance of movement from start to target center  W = width of the target  non-mathematically movement time a logarithmic function of distance (target size held constant) movement time a logarithmic function of target size (distance held constant)  used in speed experiments

Sensory Perceptions and Implications for Design: Vision  Guidelines for visual display Characters in displays must be readable. Fonts should be as simple. Character definition should be as sharp. Characters should sufficiently contrast with the background. There should be adequate space surrounding each character. Highlighting should facilitate the task. Levels of intensity should not lead to fatigue. Underscoring used sparingly. Attention devices such as blinking, and reserve video should be used sparingly. Displays should be relatively inert. Displays should read from left to right. Navigation should be consistent.

Sensory Perceptions and Implications for Design: Audition Guidelines for Physical Characteristics of Auditory Messages: The message should be short. Useful when:  Response is time critical.  Visual field is overburdened.  User is already focusing visual attention. Nature of auditory messages  high enough frequency and intensity to be heard, but not annoying.  Duration is important.  Modulated sound will attract more attention than a continuous sound. Use sparingly The user should be allowed to turn on or off keystroke clicks.

Copyright 2006 John Wiley & Sons, Inc Audition Figure 4.2 Decibel levels for typical sounds.

Copyright 2006 John Wiley & Sons, Inc Sensory Perceptions and Implications for Design: Touch  Guidelines for haptic displays? mouse bouncing over lines haptic feedback ?????

Copyright 2006 John Wiley & Sons, Inc Other senses?  olifactory?

Copyright 2006 John Wiley & Sons, Inc Health Problems associated with HCI  Emissions: electronic radiation waves emitted by visual display terminals.  Repetitive Motion Problems: Physical discomfort and inflammation of tendons and tendon sheaths caused by frequent use of keyboards and other input devices.  Vision Problems: Blurred visions and degraded ability to see brought on by frequent use of computers.

Copyright 2006 John Wiley & Sons, Inc Health Problems associated with HCI  Muscular Problems: sore and damaged muscles brought on by frequent use of computers.  Constrained postures such as those required in prolonged computer-based work result in static muscular work and such symptoms as: Inflammation of the joints (arthritis), Inflammation of the tendon sheaths (tendonitis or peri-tendonitis), Inflammation of the attachment points of the tendons, Chronic degeneration of the joints (arthroses), Painful hardening of the muscles, and Inter-vertebral disc problems.

Copyright 2006 John Wiley & Sons, Inc Technical Support for the Disabled  Technical support for the visually impaired: software and hardware design that accommodates visually impaired users.  Technical support for the hearing impaired: software and hardware design that accommodates hearing impaired users.  Technical support for the physically disabled: software and hardware design that accommodates physically disabled users.