  We present a structured random-walk model that captures key aspects of how
people communicate in groups. Our model takes the form of a correlated L\'{e}vy
flight that quantifies the balance between focused discussion of an idea and
long-distance leaps in semantic space. We apply our model to three cases of
increasing structural complexity: philosophical texts by Aristotle, Hume, and
Kant; four days of parliamentary debate during the French Revolution; and
branching comment trees on the discussion website Reddit. In the philosophical
and parliamentary cases, the model parameters that describe this balance
converge under coarse-graining to limit regions that demonstrate the emergence
of large-scale structure, a result which is robust to translation between
languages. Meanwhile, we find that the political forum we consider on Reddit
exhibits a debate-like pattern, while communities dedicated to the discussion
of science and news show much less temporal order, and may make use of the
emergent, tree-like topology of comment replies to structure their epistemic
explorations. Our model allows us to quantify the ways in which social
technologies such as parliamentary procedures and online commenting systems
shape the joint exploration of ideas.
