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The Design of Everyday Things: Book Review
November 1, 2022

#### Introduction

The Design of Everyday Things by Donald Norman has had a profound impact on my engineering career. Why should a DSP or RF engineer read a book about light switches, door knobs and telephone keypads? Read on to find out!

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#### Mental Models

I read The Design of Everyday Things when I was getting my MSEE and it completely changed how I thought about designing, engineering, and communication.

As a student I found it difficult to communicate complicated thoughts such as , what a signal’s phase is, or why the Discrete Fourier Transform (DFT) works. I understood the concepts but I could not explain them to anyone else.

The book introduces the powerful concept of a ”mental model”. The user of an object needs to have an understanding of how it works and a simple understanding is best. It is the job of the designer (or engineer) to design the system to be clear and intuitive. Complex and difficult to understand objects and systems will cause the user to feel dumb and thus the object will be discarded. Fail!

#### Simplify when Communcating

DSP and RF engineers do not design products that interface directly with humans. Typically DSP and RF engineers are designing hardware, software or algorithms which interface with other electronics.

However!

Engineers still have to communicate their thoughts, ideas and plans to their customers, co-workers, program managers and other people involved in the product of a system.

Using lessons learned from Everyday Things, provide everyone interested and invested in your work with mental models. Describe the operation using simple language and simple concepts to drive the point home. In many cases it will be useful to over simplify, leaving out detailed information about the operation which the user may not be prepared for or have time to discuss.

How do you provide a simple mental model?

1. Use pictures and images whenever possible to communicate

2. Use math to support and justify your work, but do not use it to explain your work. Math is hard to understand for broad swaths of the population and your audience may not have the same mathematical expertise and experience as you do.

#### Examples of Mental Models

A mental model paradox: the most accurate technical descriptions of a system is often too difficult to understand for the user and it should not be communicated to them. The best mental models are so over-simplified that they begin to lose information and present a some-what inaccurate representation.

Let’s take a look at a two examples, both describing the operation of an automobile.

Bad mental model: a car requires a highly coordinated symbiotic dance between the fuel combustion system, the electric system and the mechanical systems. The battery provides the energy to start the ignition, beginning the combustion process and starting the mechanical movement. Once the engine is running the alternator will convert physical movement into electrical energy by rotating magnets around a coil, causing a change in the magnetic flux which creates current in the coil, which is used to recharge the battery.  Pressing the gas pedal increases the amount of fuel injected into the engine, increasing the energy created into combustion and propelling the vehicle faster. The brake pedal converts excess velocity into heat by pressing the brake pad against the brake disc, converting kinetic energy into heat through friction and stopping the vehicle.

Good mental model: put the key in, then press the gas pedal to go forward, and press the brake to stop.

#### Conclusion

The Design of Everyday Things is an incredible book for engineers and I highly suggest buying a copy. The book introduces the concept of a mental model which describes how people perceive a system operates. Designing systems to have simpler mental models makes them easier to use. DSP and RF engineers can use the mental model concept to describe their systems to their co-workers, program managers and customers in ways that makes them easy to understand.

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God, the Lord, is my strength; He makes my feet like the deer's; He makes me tread on my high places. Habakkuk 3:19
For everything there is a season, and a time for every matter under heaven. A time to cast away stones, and a time to gather stones together. A time to embrace, and a time to refrain from embracing. Ecclesiastes 3:1,5
The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters. Genesis 1:2
Behold, I am toward God as you are; I too was pinched off from a piece of clay. Job 33:6
Enter His gates with thanksgiving, and His courts with praise! Give thanks to Him; bless His name! Psalm 100:4
Lift up your hands to the holy place and bless the Lord! Psalm 134:2
Blessed is the man who trusts in the Lord, whose trust is the Lord. He is like a tree planted by water, that sends out its roots by the stream, and does not fear when heat comes, for its leaves remain green, and is not anxious in the year of drought, for it does not cease to bear fruit. Jeremiah 17:7-8
He said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets.” Matthew 22:37-39
Then He said to me, “Prophesy over these bones, and say to them, O dry bones, hear the word of the Lord. Thus says the Lord God to these bones: Behold, I will cause breath to enter you, and you shall live." Ezekiel 37:4-5
Riches do not profit in the day of wrath, but righteousness delivers from death. Proverbs 11:4
The angel of the Lord appeared to him in a flame of fire out of the midst of a bush. He looked, and behold, the bush was burning, yet it was not consumed. And Moses said, “I will turn aside to see this great sight, why the bush is not burned.” When the Lord saw that he turned aside to see, God called to him out of the bush, “Moses, Moses!” And he said, “Here I am.” Exodus 3:2-3
Daniel answered and said: “Blessed be the name of God forever and ever, to whom belong wisdom and might. He changes times and seasons; He removes kings and sets up kings; He gives wisdom to the wise and knowledge to those who have understanding." Daniel 2:20-21
Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 2 Corinthians 3:17

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