  In this paper we present first experimental results about a small group of
people exchanging private and public messages in a virtual community. Our goal
is the study of the cognitive network that emerges during a chat seance. We
used the Derrida coefficient and the triangle structure under the working
assumption that moods and perceived mutual affinity can produce results
complementary to a full semantic analysis. The most outstanding outcome is the
difference between the network obtained considering publicly exchanged messages
and the one considering only privately exchanged messages: in the former case,
the network is very homogeneous, in the sense that each individual interacts in
the same way with all the participants, whilst in the latter the interactions
among different agents are very heterogeneous, and are based on "the enemy of
my enemy is my friend" strategy. Finally a recent characterization of the
triangular cliques has been considered in order to describe the intimate
structure of the network. Experimental results confirm recent theoretical
studies indicating that certain 3-vertex structures can be used as indicators
for the network aging and some relevant dynamical features.
