Psychology & Work Today

1. Psychology & Work Today Engineering Psychology

2. Learning Objectives After reading this chapter, students should be able to: • Define ergonomics and describe its role and function in the workplace • Outline the history and scope of engineering psychology • Explain the relationship of displays, controls, and the human operator in a person-machine system • Describe the major considerations involved in the design of a workspace • Contrast the advantages and disadvantages of auditory and visual presentation of information • Define telematics and its importance to engineering psychology • Describe the use of human factors in everyday life, with examples • Understand and explain the factors that should be considered in the design of a computer work station

3. What is Engineering Psychology? • The design of machines and equipment for human use, and the determination of the appropriate human behaviors for the efficient operation of the machines • Also called • Human factors • Human engineering • Ergonomics

4. History and Scope of Engineering Psychology • Prior to 1940, engineers made machines without considering the human factor • The worker was adapted to the machine through time-and-motion studies • WW II weaponry was complex but did not perform up to expectations, thus giving rise to engineering psychology • Example: There was no consistency in design of aircraft controls. “On” position for some controls was up, for others, down – difficult to remember in a dog fight. Many pilots died as a result

5. History and Scope of Engineering Psychology • Poor design resulted in many accidents • Three Mile Island in 1979 - poor design of controls • NTSB added engineering psychologists to its staff to study pilot error • Human factors research resulted in safer automobiles, including redesigns of headlights, brake lights, and tinted windows • Other areas of effort include license plate visibility, signage, cell phone use while driving, driver aggression, and mailbag design • Ergonomics has net gains of 1 to 12% over the costs of human factors interventions

6. Engineering Psychology is a Hybrid • Members of the Human Factors and Ergonomics Society includes: • Psychologists • Engineers • Medicine • Sociology • Anthropology • Computer sciences • Other behavioral and physical sciences

7. Time and Motion Study • An early attempt to redesign work tools and to reshape the way workers performed routine, repetitive jobs • F.W. Taylor (1898) performed first empirical demonstration of the relationship between work tools and worker efficiency • Introduced shovels of different sizes for handling different materials • 21 1/2 pounds was the most efficient load at a U.S. Steel company study • Saved the company $78,000 per year

8. Time and Motion Study • Frank and Lillian Gilbreth (1911) were interested in the mechanics of job performance to eliminate unnecessary motion • Started with improving the efficiency of bricklaying • Increased rate of bricklaying from 120 to 350 bricks an hour by reducing motions from 18 to 5 • The basic unit of motion was the Therblig (Gilbreth spelled backwards) • Gilbreth’s had 12 children – their lives were depicted in the movie Cheaper by the Dozen • More info at http://gilbrethnetwork.tripod.com

9. Guidelines for Increasing Efficiency of Manual Jobs • Minimize reaching distance from worker • Symmetrical movements of both hands • Hands should never be idle • Hands never do tasks that can be performed by other parts of body • Workbench height adjusted to prevent fatigue

10. Person-Machine System • A system in which human and mechanical components operate together to accomplish a task • Human operator receives input on machine status from the displays • Such systems vary in the extent to which the human operator is actively and continuously involved • Humans remain important components of automated manufacturing systems • Automation makes the engineering psychologists job more demanding as monitoring machinery is more monotonous than actually operating it

11. Allocating Functions Between The Operator & Machine • Engineers first carefully analyze each process in the functioning of the total system to determine its characteristics • Speed, accuracy and frequency with which it is performed • Stress under which occurs • They then make decisions regarding man - machine division of labor

12. Machine Strengths • Detecting stimuli beyond human sensory capacities • Monitoring reliability for lengthy periods • Making large numbers of rapid, accurate calculations • Storing and retrieving vast amounts of information • Applying continuous and rapid physical force • Engaging in repetitive activities

13. Machine Limitations • Not very flexible • Cannot learn from errors • Cannot improvise • When operators only monitor, disastrous results can happen • e.g., bored pilots or subway drivers • However, full automation is dangerous as systems can fail – no intervention available without human monitor

14. Principles for Workspace Design • All materials should be placed in order in which they will be used so paths of movements will be continuous • Tools should be pre-positioned for use • All parts and tools should be within comfortable reach • Greater than about 28 inches causes unnecessary repositioning and consequent loss of efficiency and increased fatigue

15. Other Design Considerations • Heights of all working surfaces should be adjustable • Hand tools should be designed for use without bending wrists • Hammers with angled handles work better • Properly designed tools affect productivity, satisfaction, and physical health • e.g., reduction of carpal tunnel syndrome

16. Human Anthropometry • A branch of engineering psychology concerned with measurements of the physical structure of the body, including • Height – standing and sitting • Shoulder breadth • Back height • Chest depth • Foot and hand length • Knee angle • These measurements are applied to design of work areas to determine normal and maximum reaching distances, tool and desk height and arrangement, etc.

17. Presenting Visual Information in Displays • Visual presentation is most appropriate when • Message is long, difficult and abstract. Visuals help to clarify. • Environment is too noisy for auditory signals • Auditory channels are overloaded • Multiple kinds of information presented simultaneously

18. Auditory Presentation of Information • Auditory presentation is most effective when: • Information is short, simple, and straightforward • Message is urgent • Environment is too dark for visuals • The operator’s job requires moving to different locations

19. Types of Visual Displays • Quantitative displays present a precise numerical value such as speed, altitude or temperature • An open window display is read with fewest errors, and the vertical display was misread one third of the time • Digital display can be read faster with fewer errors, but cannot be used in all situations • e.g., if conditions are rapidly changing, or need to know direction of change

20. Qualitative Displays • Displays that present a range rather than a precise numerical value • e.g., red area hot – green area normal – yellow area cold • Consistent patterning makes multiple displays easier to read • Used in aircraft cockpits • Unpatterned displays force operator to read each dial separately

21. Check Reading Visual Displays • Simplest kind of visual display • Tells operator whether the system is: • On or off • Safe or unsafe • Normal or abnormal • Warning light most common • Twice as bright as background • Centered in field of vision • Flashing

22. Auditory Displays • Auditory displays can be more compelling than visual because • Ears are always open • Sound can be multi-directional • Where as visual is often taxed to capacity • Problem with “nuisance alarms” • If alarms are too sensitive or occur too frequently, they are often ignored

23. Guidelines For Controls • Control-body matching • Mostly rely on hands and feet • No single limb should be given too many tasks • Control-task compatibility • A control action should imitate the movements it produces • Turning steering wheel right makes right turn • When possible, combining controls that perform similar or related functions. This is more efficient

24. Guidelines For Controls • Identification of controls • Controls should be clearly marked or coded • e.g., shape coding for touch recognition • Placement of controls • Consistency and uniformity is important • Consider cultural influences on preferences • Emergency controls in line of sight, clearly distinguishable and protected with a cover • Group related controls and displays according to function

25. Human Factors in Everyday Life • Human factors no longer confined to tanks, airplanes and work areas • Telematics deals with wireless information technology such as GPS, Satellite radio, and built-in wireless phone for cars • Ergonomics also includes examining cell phone use while driving (to prevent accidents) • Use of auditory signals to alert drivers which are too close to another car • Spatulas that reduce risk of carpal tunnel, such as sharpened ice cream scoops….

26. Computers • Poorly designed computers and work stations produce strain and discomfort • Eyestrain and blurred vision • Fatigue and pain • Comfort range for keyboard operation is an angle of 7-20 degrees with an elbow angle of 90 degrees • Optimal viewing distance of 15 to 30 inches • Optimal screen height is 33-42 inches • Mouse redesigned to reduce movements

27. Key Terms • Auditory displays • Check reading visual displays • Engineering psychology • Human anthropology • Person-machine systems • Qualitative visual displays • Quantitative visual displays • Shape coding • Time-and-motion study