Fig. 1.

When people estimate how deeply they understand the workings of various systems, they tend to think they know for more depth of detail than they actually do. When asked how a helicopter works, they seem to think they have knowledge approximating a detailed annotated drawing, but actually have a much coarser understanding corresponding to little more than the sense of a thing with blades that turn and provide lift. This illusion is quite specific to explanatory kinds of knowledge. People estimate the depth of their knowledge of procedures, facts and narratives much more accurately. From Keil (2003). Adapted with permission from [51]. Wright, M., Patel, M. eds (2000) How Things Work Today, Crown Publishers, New York