1. Center for Psychobiological and Psychosomatic Research, University of Trier (M.H., G.M., S.W., D.H.H.), D-54286 Trier, Germany
2. Department of Clinical Psychology, University of Zurich (M.H., U.E.), CH-8044 Zurich, Switzerland
3. Department of Zoology, University of Regensburg (I.N.), D-93040 Regensburg, Germany
4. Institute of Experimental Psychology II, University of Dusseldorf (C.K.), D-40225 Dusseldorf, Germany