In this article, the authors describe the photo language method, a technique used in clinical groups and developed by psychoanalysts in Lyon. They analyse the clinical recommendation of group devices, which use a mediating object, for patients in whom mental impairment imposes limits and therefore requires flexibility of the three constants of psychoanalytical practice: free association, transference and interpretation. The authors then compare the use of this group device, in which photographs are used as the mediating object, with other group methods in which such an object is not used, as weil as comparing it to individu al methods which use a mediating object. Finally, the authors discuss the synergy between the group and the mediating object to try and highlight sorne unconscious mental processes and verify their specificities, illustrating these with a clinical vignette of psychosomatic patients