Knowledge: In the Head & In the World

Norman uses the phrases "knowledge in the world" and "knowledge in the head" to distinguish between knowledge that exists in one's memory and information that one gains from observing and interacting with external structures. Knowledge in the head requires storage and retrieval as well as effort spent towards gaining that knowledge. Knowledge in the world requires no learning other than maybe knowing where to look. Signifiers, physical constraints, and natural mappings are ways in which knowledge exists in the world.

World-Knowledge

When it comes to cooking and preparing food, I almost always rely on a recipe. Recipes and preparation instructions are examples of knowledge that exists in the world. Rather then make an effort to memorize the proper proportion of ingredients to prepare a specific serving size of oatmeal, for example, I often rely on the instructions conveniently displayed on the oatmeal container. 

Head-Knowledge

Many digital single lens reflex (DSLR) cameras come with a combination of buttons, switches, and dials. In order translate what I see into an image, I have gained knowledge about what each of the controls do as well as knowledge about how the controls work. This is knowledge that exists in my head. I must be able to call upon it quickly in order to dial-in the "correct" settings, especially when photographing moments that are brief.

World-Knowledge & Head-Knowledge

Norman uses stoves to discuss how mappings are an example of where knowledge exists both in the world and in the head. As shown in the image, my stove includes controls that are arranged in the same spatial configuration as the objects to be controlled. In some instances, I accidentally associate a control with the wrong burner because I think in terms of proximity of control to burner rather then spatial mapping. In order to make the write decision about which burner I want to turn-on, I must  use "head-knowledge" to recall the spatial mapping. I can then use the spatial mapping, a form of "world-knowledge", to turn on the desired burner.