Book Reading #8 - Design of Everyday Things

Chapter 3: Knowledge in the Head and in the World

Summary:

In this chapter, Donald Norman talks about how we store and retrieve information (knowledge) in our brain. He claims that because not all the knowledge required for the precise behavior has to be in the head, it can be distributed partly in the head and partly in the world. Whenever the information needed to perform a task is readily available in the world, the need to memorize it diminishes. For example, if you can store someone's cellphone number in your contact list, you don't have to remember it anymore since it's readily accessible. People store information in the form of two types of knowledge - knowledge of: this consists of knowledge of facts and rules while knowledge how is procedural knowledge, i.e. knowledge of how to perform a particular action. It is best taught through action and best learnt through practice since it is largely subconscious.

It is a general property of memory that we store only partial descriptions of the things to be remembered, descriptions that are sufficiently precise to work at the time something is learned, but that may not work later on, when new experiences have also been encountered and entered into memory. The author states that there are so many things that we have to memorize, like passwords, account numbers, phone numbers, driver's license number, social security number, credit card numbers, postal codes, passport number, birthdays etc. It is important to understand how our memory works since we totally rely on it for our everyday activities. The memory is structured in to short term memory which is small in size and volatile, just like the caches in the computer memory. On the other hand the long term memory is large, and the information stored can be retained for years, just like the disks.

Mental models simplify learning, in part because the details of the required behavior can be derived when needed. They can be invaluable when dealing with unexpected situations. The author mentions that we often need to be reminded to do something. If the thing to be done is not in our interest, we often put that responsibility on the other, else we try to write things down on hands, take notes, mark dates on calenders etc. Finally, the author talks about natural mapping. He claims that natural mapping can reduce confusion and help remember things. For example, the turn signal button on a motorcycle - if the left turn signal is turned on if the button is lid towards left and the right turn signal is powered if the button is slid towards right, then it's a natural mapping. This can make devices self intuitive.

Discussion:

It was interesting to read how the author has studied human memory and its functioning to minute details. I also realized that the computer memory resembles the human memory in architecture even though its retrieval rates are slow and capacity is limited. The examples provided by the author make the topic very interesting and clear to understand. I think it's very important to understand how human memory works to make most efficient use of it and the knowledge can be applied to design smart and easy-to-use machines.