Wigner’s Friend Revitalized?

Abstract

In contemporary quantum physics, Schrödinger’s cat is not regarded as a real problem but as a metaphor to illustrate the measurement problem. In the same spirit, the metaphor of Wigner’s friend is considered as an extreme subjectivistic interpretation without any sound theoretical or empirical basis. In the present paper experimental results will be discussed which may lead to a reconsideration of Wigner’s original idea of an “observer effect”. The results of the reported experiments, however, show that the concept of an “observer influence” is misleading because there is no signal transfer, which may be responsible for the measured correlations between human observers and the observed quantum physical process. It is argued that the effect is an emerging property of macroscopic self-referential psycho-physical systems, which is phenomenologically equivalent to non-local EPR-correlations known in quantum physics. For an appropriate interpretation, physical and psychological arguments are required, and the distinction of exo- and endodescriptions is of crucial importance. The model of pragmatic information (MPI) describes the observer effect in terms of pseudo-signals in hierarchically nested endoexo-systems which may to some extent be able to reconcile the Cartesian separation of res extensa and res cogitans.