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Ah, The Joy of Spring Term

PSY330 Human Factors Honor Thy User There are Always Tradeoffs

Business Roll Call Review Syllabus http://psychlab1.hanover.edu/Classes/HumanFactors/2001/psy330.html Meeting Times (MTWRF 9-12 most days) Office Hours (Class will pick) Assignments - Depends on final number in class One Test 100 points Two Presentations 200 points Two Short Papers 100 points Class and Homework Problems   50 Points Active Participation 150 Points Total 600 points Grading - 10% for each letter grade

Detailed Description of Three-Mile Island 4:00 am, March 28, 1979 Main feedwater pump stops due to a polisher blocking coolant flow due to resin build up. Resulting Hardware Effects and Actions: Electrical generators and turbines shut down. Temperature of water in the reactor rises. Pressure in reactor water builds and escapes from relief valve. control rods automatically drop stopping the nuclear reactions. emergency feedwater pump starts This should have been a mild failure - unworthy of news attention.

Three Mile Island - The Disaster Mechanical Failure NO water was getting to the emergency pump - the lines were closed one light signaling that lines were closed was covered by a maintenance tag. other light - who knows? The relief valve did not close With valve open, radioactive water escaped to drain tank. Human Factors Issue Visibility of alerts Placement is also an issue Relief valve lights indicated commanded state not actual state - that they were switched to close that that they did close

Three Mile Island - The Disaster - 2 Action Over 100 alarms went off in two minutes Computer printer was hopelessly behind the times - 1 item every 4 seconds. Human Factors Issue Limits of Short-term memory Limits of attention Response selection

Three Mile Island - The Disaster (cont.) When the steam generators boiled dry standby pumps began to operate, as they should Operators turned down the flow thinking enough coolant was available - kept problem growing. Practically an accidental turning on of the standby pumps by a supervisor averted the accident.

Three Mile Island - Summary Human intervention was primary cause of accident But the reasons for the errors by the operators predate the building of the plant The Human Error was principally due to design of the control room Note: While there was human error, it was not the operators fault A recent change in shift may also have played a role.

A Minor Disaster Closer to Home Background Oven controls are not standard - off on different ovens are different directions. The previous oven control turned counter-clockwise for off. The oven under consideration turned clockwise for off. The Event A very nice apple crisp was being made. It had completed it before supper. It got very crisp - turned on broiler instead. The nonstandardized controls between units led to proactive interference.

What is Common here? Human error occurred. The equipment acted as designed. But did the design have a role in the error? What features of human psychology might have played a role? Might a knowledge of psychology have helped avert these errors?  How?

Definitions of Human Factors The design of equipment that people use intentionally taking into account how people operate. (Syllabus) The field of human factors engineering uses scientific knowledge about human behavior in specifying the design and use of a human-machine system.  (Adams, 1989). Human factors discovers and applies information about human behaviors, abilities, limitations, and other characteristics to the design of tools, machines, systems, tasks, jobs, and environment for productive, safe, comfortable and effective human use. Chapanis (1985)

Some Historical Antecedents of Human Factors Measurements of Human Performance Weber's Law: DI/I=k Gives ability to discriminate, that is tell differences Reading numbers off a display in various lighting situations Knowing what color is being seen

Human Performance - Weber’s Law

Human Performance - Weber’s Law

Human Performance - Weber's Law

Human Performance - Weber's Law 2

Human Performance - Weber's Law 3

Human Performance Steven’s Law: S=cIb Deals not with discrimination but perception of size of differences when they are easy to perceive How much louder is one sound than another How far away is the oncoming train

Some Historical Antecedents of Human Factors - 2 Human Information Processing Sees us as acquiring and transforming information. Human Performance in Applied Settings Babbage and Economy of Machinery and Manufactures Emphasizes productivity Biomechanics and Physiology Examines mechanical nature of human movement

Fundamental Principles of Human Factors Honor Thy User! It is our job to take the user’s perspective We are the users advocate with the designers and producers of the system under consideration. There are always tradeoffs! Differing goals will always conflict and need to be balanced. To enhance one feature of a system will minimize others. It is possible and likely that both features of the system are important and desirable.

Objectives and Design of the Course Gain Background in Human Factors Review or relevant knowledge - First 2 weeks Culminates in an examination on second Thursday of term Readings for other assignments. Apply Human Factors Knowledge This can be accomplished in three common types of tasks: Design of a new system Evaluation of an existing system. Data collection and analysis

Overview of Key Human Factors Concepts The Task or Job DEFINITION: Any behavior with a goal. For example: What are the tasks of a car? What are the tasks of a word processing program? What are the tasks of a computer?

Overview of Key Human Factors Concepts The System DEFINITION: a set of connected things or parts that form a whole or work together. (Oxford American Dictionary) A system is what performs the task or job

Overview of Human-Machine Systems

Implications of the System Concept (after Proctor and van Zandt, 1994) The user or operator is part of the system The system goals are superordinate Know the purpose of the system. Systems are usually hierarchical Both systems and components have inputs and outputs Know the structure of the system Deficiencies in system performance is the result of deficiencies of one or more components. The system is part of the larger environment

Levels of Human-Machine System interactions 1.  Person supplies power and control For example a shovel system lies dormant without person using it (Kantowitz and Sorkin, 1983)

Levels of Human-Machine System interactions 2.  Machine supplies power; person control For example welding equipment can operate without human but will not accomplish anything In fact they are often very dangerous because the lack control (Kantowitz and Sorkin, 1983)

Levels of Human-Machine System interactions 3.  Machine supplies power and information; person still controls For example most factories System can work to a some extent on own.  Needs constant monitoring since cannot control Thus, a low level of automation (Kantowitz and Sorkin, 1983)

Levels of Human-Machine System interactions 4.  Machine supplies power, information and control; person monitors For example Boeing 757/767 and other advanced aircraft when autopilot is engaged These are highly automated systems Human in many cases are primarily error detectors If role is too small human may feel irrelevant or uninvolved (Kantowitz and Sorkin, 1983)

Theory of System Operation: Control Systems Theory Types of control open-loop: feedback is not in time to alter action, error cannot be corrected during the act - Typing closed loop: feedback occur such that error can be corrected during the task - Driving Elements of a Control System A control system is closed loop Uses negative feedback The thermostat is an example

A Model of Control Systems Theory

A Model of Control Systems Theory

A Model of Control Systems Theory

What is a Human Factors Professional Training (Survey of membership of Human Factors Society in 1986.) 49% trained in psychology - most have Ph.D.s. 14.5% trained in engineering. 6.8% trained in specialized Human Factors Programs. 37% overall have Ph.D.s.

What is a Human Factors Professional - 2 Where do human factors engineers work Industry: 39% (Aerospace and Computer/Software were largest percentage). Business: 19% Government: 20% Academia: 18%

What is a Human Factors Professional - 3 Common Activities of human factors engineers. Write Reports - most commonly listed item. Formal briefings and presentations. Schedule project activities/manage others. Determine system requirements. Verify system designs meets human factors standards. Write system goals and objectives. Develop experiments to test theories or systems. Examples

Discussion of Projects Project (From Syllabus): Interface for CD-ROM version of Dr. Barlow’s new book. Interface in book and computer for my in development Sensation and Perception Text Not sure order yet.