The ‘self’ is increasingly used as a variable in cognitive experiments and correlated with activity in particular areas in the brain. At first glance, this seems to transform the self from an ephemeral theoretical entity to something concrete and measurable. However, the transformation is by no means unproblematic. We trace the development of two important experimental paradigms in the study of the self, self-face recognition and the adjective self ascription task. We show how the experimental instrumentalization has gone hand in (...) hand with a simplification of the self-concept, and how more conceptual and theoretical reflections on the structure, function and nature of self have either disappeared altogether or receded into the background. We argue that this development impedes and complicates the interdisciplinary study of self. (shrink)