  The main result of this letter is that SOC naturally arises as a result of
memory effects. We show that memory effects provide the mechanism for self
organization. A general procedure to investigate this issue in models that
display self organized critical behaviour is proposed and applied to some
example. The simplest class of models exhibiting self organized criticality
through this mechanism is introduced and discussed in some detail. PACS:
02.50-r, 05.40+j, 05.40jk
