Design of Everyday Things Excerpt - Chapter 5 Human Error? No, Bad Design

Also refer to https://medium.com/@yuuychien/key-takeaways-from-the-design-of-everyday-things-chapter-5-a1e627fc5b10
https://www.garethrees.co.uk/2017/12/23/book-notes-the-design-of-everyday-things/

Why there is a error?

Human error is defined as any deviation from (generally accepted) appropriate behavior.
The most common is in the nature of the tasks and procedures that require people to behave in unnatural ways. People are forced to serve machine and become dull and may be punished. (p.168)
Interruption is another common reason.
Time stress

• Root Cause Analysis: to discover a human error in the chain, to understand why the error occurred, and to know what can be done to prevent it. 
• Five Whys: find one reason, ask why that was the case. And then why again. Keep asking until you have uncovered the true underlying causes.

Two Types of Errors: Slips (lower level) and Mistakes (higher level of cognition)

1. Slips: when the goal is correct, but the required actions are not done properly: the execution is flawed.
   • action-based - the wrong action is performed
   • memory lapses (when the memory failure was at the lower (subconscious) levels - slips) - the intended action is not done or its results not evaluated, e.g. forgetting to turn off gas burner after cooking.
2. Mistakes: it occurs when the wrong goal is established or the wrong plan is performed.
   • rule-based - the wrong rule is being followed even the situation is properly diagnosed. The cure: Designers should provide as much guidance as possible to ensure the current state of things is displayed in a coherent and easily interpreted format. Provide alternative explanations and interpretations. (p.182-184)
   • knowledge-based - the problem is misdiagnosed due to erroneous or incomplete knowledge. The cure: Good procedural manuals will be helpful
   • memory lapses (when the memory failure was at the highest level of cognition - mistake) - -forgetting at the stages of goals, plans, or evaluation, e.g. a mechanic fails to complete oil change because of distraction. Interruptions is a common cause in memory-lapse mistakes. The design curers for this is the same with memory-lapse slips - ensure that all the relevant information is continuously available.

Classification of Slips

• Capture slips: When a frequently done activity suddenly takes charge instead of the one intended.
• Description-Similarity slips: Performing the correct action on the wrong object. Occur most frequently when the wrong and right objects are physically near each other. A lineup of identical-looking switches or display is a very apt to lead to description-similarity error. Design of controls and displays for different purposes need to be differentiated.
• Mode Error slips: When a device has different modes (states) in which the same controls have different meanings. Especially likely when the equipment does not make the mode visible. Problem: more and more functions are added to our devices - it's tempting to save money and space by having a single control serve multiple purposes. The apparent simplicity masks the underlying complexity of use. The cure: Modes must be made visible/obvious, or try to avoid modes.
• Memory-Lapse Slips: the immediate cause is interruption, e.g. too many steps to operate a machine. The cures include: minimize the number of steps, and forcing function (Chapter 4), e.g. a user must take a bank card out of ATM before it dispense money.

Checklists

Reporting Error

Make it easier to report errors, for the goal is not to punish, but to determine how it occurred and change things so that it will not happen again

TOYOTA Jidoka (自動化 ),  ask why as many times as necessary to determine the cause: Why did it happen? Why was that? Why is the reason?

Poka-yoke "error-proofing" A poka-yoke is any mechanism in any process that helps an equipment operator avoid (yokeru) mistakes (poka) - using fixtures, jigs or devices, DFM, DFMA to constrain the operations so that they are correct. Poka-Yoke techniques involve with combination of principles - affordances, signifiers, mapping, and constraints, and most important of all, forcing functions.

Automate the error reporting process, even though it stops production. Then avoid the same error by error proofing

Designing for Error

• Understand the causes of error and design to minimize those causes
• Do sensibility checks. Does the action pass the "common sense" test?
• Make it possible to reverse actions - to "undo" them - or make it harder to do what cannot be reversed
  • Add constraints to block errors - "Do you want to delete this file? Are you sure?"
• Make it easier for people to discover the errors that do occur, and make them easier to correct
• Don't treat the action as an error; rather, try to help the person complete the action properly. Think of the action as an approximation to what is desired
• (my addition: provide an alternative or detour to complete a task)

Multitasking severe degradation of performance, increased errors, and a general lack of both quality and efficiency. Doing 2 tasks at once takes longer than the sum of time it takes to do each alone.

Design Lessons from the Study of Errors 

• Adding constraints to block errors - e.g. forcing functions
• Undo 
• Confirmation and error messages
• Make the item being acted upon more prominent: - Change the color, enlarge it
• Make the operation reversible: - Auto save to prevent closing it by accident

Sensibility Check

Electronic (intelligent) system can check to make sure that the requested operation is sensible. It is an answer to the serious errors caused when inappropriate values are entered into system, e.g. the intelligent system at a bank would take note of the normal size of a customer's transactions, querying if the amount is larger than normal.

Minimizing Slips

• provide feedback
• no rows of identical controls or meters - a source of description-similarity errors
• internal modes must be visible, distinct, and very conspicuously marked to avoid mode errors
• eliminate unnecessary modes
• reduce number of interruptions to avoid memory slips

Reason's Swiss Cheese Model of Accidents - How Errors Lead to Accidents

Accidents usually have multiple causes, whereby had any single on of those causes not happened, the accident would not have occurred. Unless the holes (errors) on the cheeses all line up perfectly, there will be no accident. The Swiss cheese metaphor suggests several ways to reduce accidents:

• Add more slice of cheese - designed precaution against error
• Reduce the number of holes (or make the existing holes smaller) - errors
• Alert the human operators when several holes have lined up - when errors all occur simutaneously

Design Redundancy and Layers of Defense is Swiss cheese

When Good Design Isn't Enough

When people really are at fault

People can lose competency if sleep deprived, fatigued, or under the influence of drugs, or lack of training, or deliberate violation

The far greater percentage of accidents is the result of poor design, either of equipment or, as is often the case in industrial accidents, of the procedures to be followed

Resilience Engineering

Sometimes the problems do not arise in the organization but outside it - natural disasters for example

The question is how to design and manage these systems so that they can restore services with a minimum of disruption and damage. The system is designed in anticipating the changing potential for failure.

The Paradox of Automation

When automation works, it is wonderful, but when it fails, the resulting impact is usually unexpected, as a result, dangerous. When the failure occurs, human is out of the loop.

Design Principles for Dealing with Error

People: flexible, versatile, and creative Machines: rigid, precise, and relatively fixed in their operations.  Difficulties arise when we do not think of people and machines as collaborative systems. Human plus computer is a perfect collaboration. 

Human error flags a deficit in our technology. It should not be thought of as error. We should eliminate the concept of error: instead, we should realize that people can use assistance in translating their goals and plans into the appropriate form for technology. 

Given the mismatch between human competencies and technological requirements, errors are inevitable. Therefore, the best designs take that fact as given and seek to minimize the opportunities for errors while also mitigating the consequences.

Design principles:

• Put the knowledge required to operate the technology in the world
• Use the power of natural and artificial constraints: physical, logical, semantic, and cultural
  • Exploit the power of forcing functions and natural mappings
• Bridge the two gulfs, the Gulf of Execution and the Gulf of Evaluation
• Make things visible, both for execution and evaluation
  • On the execution side: provide feedforward information - make the options readily available
  • On the evaluation side: provide feedback information - make the results of each action apparent
• Make it possible to determine the system's status readily, easily, accurately, and in a form consistent with the person's goals, plans, and expectations
• (my addition: Redundancy)
• (my addition: layers of defense)
• (my addition: add constraints) -Poka-Yoke
• (my addition: reversible, undo)