  A phenomenological model for the calculation of reduction probabilities of a
superposition of several states is presented. The approach bases only the idea
that quantum state reduction has its origin in a mutual physical interaction
between the states. The model is explicitly worked out for the gravitational
reduction hypothesis of Diosi and Penrose. It agrees for typical quantum
mechanical experiments with the projection postulate and predicts regimes in
which other behavior could be observed. An outlook is given, how the new
effects can possibly become of interest for biology. For verification a
feasible quantum optical experiment is proposed. The approach is analyzed from
the view point of quantum non-locality in concrete its consequences for
signalling.
