[Week 5] Bookclub: Human Error? No, Bad Design




The discussion continues with chapter 5. (After some time :slight_smile: ). This chapter had some heavy content and took some time to complete. Expecting to see some interesting thoughts/questions/comments.


The chapter begins with don debating that even though the majority of accidents are blamed on human error, it is actually down to bad design. When investigating the cause of an accident it is important not to stop at the human error but go beyond and see what caused the human error. One method to find the root cause analysis is the ‘5 Whys’ where you keep on digging in a cause and effect manner. Another model of analysis is the Swiss cheese model which takes into account that there are multiple causes of an accident and you need to determine each of these causes.

Don classifies errors into Slips and Mistakes. Slips are when you have the correct plan in mind but falter in execution. Mistakes happen when you have the wrong plan in mind and therefore the execution is doomed to fail. Slips are further classified into action slips and memory slips. Mistakes are classified into rule based mistakes, knowledge based mistakes and memory based mistakes. Slips frequently happen in digital products with people clicking the wrong target for their action or forgetting an action. Mistakes frequently occur when there is not enough knowledge provided for the user to make the correct decision.

Why do people make these errors? Interruptions, multitasking, mental limitations, social/institutional pressure and deliberate violations.

How can we minimize errors through design? Adding constraints, providing ‘Undo’, providing timely confirmation & error messages, provide required knowlege for operation in the real world, show feedforward information, avoiding similar targets/procedures for distinct actions.

The ‘Undo’ option seems a preferred method today with products opting out of an additional confirmation while providing the undo feature.

Favourite quotes

“Physical limitations are well understood by designers; mental limitations are greatly misunderstood.”

“Error occurs for many reasons. The most common is in the nature of the tasks and procedures that require people to behave in unnatural ways”

“We should deal with error by embracing it, by seeking to understand the causes and ensuring they do not happen again”

Some discussion points

  • Examples you have come across for error prone designs and designs which have done well to handle errors
  • How do we take the mental limitations of the user into the design? (eg. Fatigue)


Thanks so much for doing this Nalin. I’ll get onto writing up my thoughts soon.


I’m behind in my reading, but I was putting together an IKEA bed today and whoa-boy-howdy, did I experience this!

If you don’t pay real close attention to the IKEA guy and the holes in the drawings, you’re going to end up having to take the whole thing apart and doing it over again.

I was mentally ranting against the IKEA guy for not being clear enough but then I shifted gears and started blaming myself for not looking closely enough.

After a bit, I remembered this thread.

What I find interesting about my experience today is that I actually felt better when I took the ‘blame’ onto myself rather than on the instructions.


Maybe that is because if you blame the instructions you have reduced the perceived value of your purchase, which may lead you to be less satisfied with the purchase.


My turn.

I was fascinated by his analysis of the airline accidents. I’m a former air traffic controller and I remember being trained on some of those incidents. One of the things we did was listen to the tapes. While Don made some very good points about the procedures that could have been better, I think he underplayed some of the human factors involved.

In the Tenerife incident, I think it’s important to note that fog happens and there are often times when aircraft can’t see each other ~ even without fog. Airports are big! While the pilot didn’t receive clearance to take off, he thought he had. It was a tragic miscommunication.

The miscommunication happened because both the pilot and the controller failed to abide by the standard phraseology.

Maybe I’m being too hard on Don because I know more details. He did say that, “although violations are a form of error, these are… outside the scope of the design of everyday things.”

I found this chapter exceptionally interesting because of my experience as a controller.

Favorite quotes:

  • If the system lets you make the error, it is badly designed. And if the system induces you to make the error, then it is really badly designed.
  • When an accident is thought to be caused by people, we blame them and then continue to do things just as we have always done.