[Sense of agency: experiencing is not judging]

Experiencing oneself as the author of an action defines the sense of agency, which is a component of the self. A deficit affecting this process is thought to cause the principle symptoms characterizing schizophrenia - e.g. delusions of control and auditive hallucinations would exist because patients do not experience themselves as the author of their own actions.

To explore this specific problem of the sense of agency in schizophrenia, Frith et al. collected a serie of experimental data that lead them to propose that the sense of agency relied on the automatic motor system, processes that enable the predictive adjustment of action. An impairment in these processes (called <> in the literature) would lead to the problem of dissociation between our own actions and those performed by others. More specifically, the problem would lay in the comparison between the predicted state and the desired state (figure 1). Jeannerod et al. from Lyon used attribution judgements that suggested that the sense of agency would not depend uniquely on the motor mechanisms but would also involve conscious processes. Recently, Frith et al. have published new data that integrates both preceding models. According to this theory, the sense of agency would depend on the processes involved in the predictive control of action but at a conscious level: the attenuation of the sensory feedback, specific of our own actions. This attenuation would depend on the accuracy of comparison between the predicted state and the actual state. Moreover, the sense of agency would also imply the management of social frame, which normally gives the means to cope with human interaction.

The conception of the sense of agency has greatly evolved over the years, mainly because of the various experimental methods employed. The consequences of this are the various theoretical interpretations given to the characteristics of the sense of agency. They can be explained in two main points: a non-unified definition of the sense of agency and an absence of experimental data testing alternative interpretations. First, protocols using attribution judgements have proven to be useful to gain better understanding of the attribution mechanism in schizophrenia. However, findings obtained with these judgments have often been used to conclude on deficits of the sense of agency in schizophrenia, whereas the sense of agency is only a sub component of these judgements.

More work must be conducted in order to show that generalization from judgements to self-agency is possible. Secondly, data have not been collected in order to go against the accepted proposition that the sense of agency (1) implies conscious processes, comes (2) secondary to action execution because based on sensory attenuation and (3) has subjective consequences only. Further studies would be useful to explore these points, so as to improve our understanding of the physiopathologyogy of schizophrenia.