DOET: Knowledge in the Head and in the World
Knowledge in the head is memory. Knowledge in the world is everything else — external information. People structure their environment i.e. personal desks to provide information for something that needs to be remembered. For example, I place all my pens in a plastic cup in a corner of my desk. I know it’s at that cup in that specific corner location that I will find my pens.
Back to knowledge in the head, there are three types of memory: memory for arbitrary things, for meaningful relationships, and for explanation.
Memory for arbitrary things is straight memorization. Learning is difficult and takes time and effort to retain. It is inapplicable to situations different from that what was memorized. For simple things such as the alphabet, it works. But when you have to memorize your postal code, friends and family’s phone numbers, birthdays, bank account numbers, etc, you become overloaded and inefficient.
Then there is memory for meaningful relationships which is retrieving information by association or triggering from familiar events. As a crude example, if I were trying to figure out how a light switch works, by associating “on” with the upward movement, I remember that flicking the switch up turns the light on. It is important to note, however, that this type of memory still doesn’t actually explain anything.
And then there is memory for explanation. Basically, to understand something. Understanding is a more powerful form of internal memory. It creates strong mental models that lend to figuring out novel situations and problems in others.
Reminders and Natural Mapping in Relation to Memory Load
Reminders are used to put knowledge into the world. They are made up of two components: (1) signal and (2) message. Many products have only one of the two satisfied.
Reminders combined with the power of natural mappings reduce the need for information in memory. Take the stove and its arrangement of controls for example. The row one has many possible combinations and is therefore confusing.
If a design depends upon labels, it may be faulty. Labels are important and often necessary, but the appropriate use of natural mappings can minimize the need for them. Whenever labels seem necessary, consider another design.
The Tradeoff between Knowledge in the World and in the Head
In design, leaning more heavily on either head or world knowledge requires tradeoffs.
Food for Thought
When you purchase products, you usually look at the aesthetics, the price, features, etc. When do you ever actually ask yourself, “Is this even usable?” Usability is seldom considered during the purchasing process.
