Collective intelligence: Web pundit Steven Johnson explains what we know about this phenomenon with a rare lucidity in Emergence: The Connected Lives of Ants, Brains, Cities, and Software. This phenomenon, known as emergence, is embodied by ''bottom-up'' systems that use ''relatively simple components to build higher-level intelligence.'' Ants build complex colonies; city residents create distinct neighborhoods, etc. In each case, developments proceed not from some central authority dictating plans from above but from the cumulative actions of low-level agents below.

Though we're far from fully understanding how complex behavior manifests from simple units and rules, our awareness that such emergence is possible is guiding research across disciplines. Readers unfamiliar with the sciences of complexity will find Emergence an excellent starting point.