  What basic processes generate hierarchy in a collective? The Bonabeau model
provides us a simple mechanism based on randomness which develops
self-organization through both winner/looser effects and relaxation process. A
phase transition between egalitarian and hierarchic states has been found both
analytically and numerically in previous works. In this paper we present a
different approach: by means of a discrete scheme we develop a mean field
approximation that not only reproduces the phase transition but also allows us
to characterize the complexity of hierarchic phase. In the same philosophy, we
study a new version of the Bonabeau model, developed by Stauffer et al. Several
previous works described numerically the presence of a similar phase transition
in this later version. We find surprising results in this model that can be
interpreted properly as the non-existence of phase transition in this version
of Bonabeau model, but a changing in fixed point structure.
