The illusion of explanatory depth (IOED) describes our belief that we understand more about the world than we actually do. Imagine an alien asks how a toilet works; you can describe the flush lever but cannot explain the internal mechanisms. This gap reveals that everyday objects like locks, car engines, or light bulbs are far less understood than we assume.

The illusion has two components: the “explanatory” part reflects our confidence in providing a clear, detailed explanation, while the “depth” part assumes that explanation will be thorough. In practice, attempting to explain exposes explanatory shallowness—our knowledge is far shallower than predicted.

Research shows the effect is far stronger for explanatory knowledge than for facts or procedures. Children as young as kindergarten overestimate their understanding. Seminal work by Rozenblit & Keil (2002) established the phenomenon, while Fernbach et al. (2013) linked it to political extremism, and Mills & Keil (2004) traced its developmental origins.

This article is authored by Dan Pilat and Dr. Sekoul Krastev, co-founders of The Decision Lab, a leading behavioral science consultancy applying these insights to organizational decision-making.