  Recent progress in the large scale mapping of social networks is opening new
quantitative windows into the structure of human societies. These networks are
largely the result of how we access and utilize information. Here I show that a
universal decision mechanism, where we base our choices upon the actions of
others, can explain much of their structure. Such collective social
arrangements emerge from successful strategies to handle information flow at
the individual level. They include the formation of closely-knit communities
and the emergence of well-connected individuals. The latter can command the
following of others while only exercising ordinary judgement.
