Background The body plays a major role in defining, understanding and treating anorexia nervosa. Much research has focused on patients' physical body representation or their own perceived body, but without explicit reference to their relationship to others and the social processes involved. Yet, there are a several arguments supporting impairments in interpersonal relationships in these patients. Notably, some evidence suggests that self/other distinction (SOD), the ability to distinguish one's own body, actions and mental representations from those of others could be impaired in anorexia. But research remains scarce in this area. Material and Methods A single-centre, prospective pilot study was conducted to investigate, for the first time, self-recognition and SOD in seven adolescents with anorexia nervosa (AN) compared with matched healthy controls (HCs) using the "Alter Ego"TM double mirror paradigm. This innovative device allows the progressive morphing of one’s own face to that of another and vice versa between two subjects that interact on opposite sides of the device. Two judgement criteria were used: 1) M1: the threshold at which subjects start to recognize their own face during other-to-self morphing, and 2) M2: the threshold at which subjects start to recognize the other’s face during self-to-other morphing. In a second part, the same procedure was reproduced under 5 different sensorimotor conditions to examine their effects on self-recognition and SOD. Results The results showed that the participants with AN exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence. Furthermore, in contrast with that of HCs, the critical threshold for switching between self and other varied with the direction of morphing in AN participants. Finally, when anorexic subjects were seated in a chair with the backrest and footrest touching their body, the self-recognition threshold (M1) increased significantly, approaching that of controls. Conclusions Although additional research is needed to replicate the results of this preliminary study, it revealed the first behavioural evidence of altered SOD in individuals with AN through an embodied, semiecological face-recognition paradigm. Relationships between body perception and alterations in interpersonal relationships are discussed as well as new research and therapeutic perspectives are presented.

Background The body plays a major role in defining, understanding and treating anorexia nervosa. Much research has focused on patients' physical body representation or their own perceived body, but without explicit reference to their relationship to others and the social processes involved. Yet, there are a several arguments supporting impairments in interpersonal relationships in these patients. Notably, some evidence suggests that self/other distinction (SOD), the ability to distinguish one's own body, actions and mental representations from those of others could be impaired in anorexia. But research remains scarce in this area. Material and Methods A single-centre, prospective pilot study was conducted to investigate, for the first time, self-recognition and SOD in seven adolescents with anorexia nervosa (AN) compared with matched healthy controls (HCs) using the "Alter Ego"TM double mirror paradigm. This innovative device allows the progressive morphing of one’s own face to that of another and vice versa between two subjects that interact on opposite sides of the device. Two judgement criteria were used: 1) M1: the threshold at which subjects start to recognize their own face during other-to-self morphing, and 2) M2: the threshold at which subjects start to recognize the other’s face during self-to-other morphing. In a second part, the same procedure was reproduced under 5 different sensorimotor conditions to examine their effects on self-recognition and SOD. Results The results showed that the participants with AN exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence. Furthermore, in contrast with that of HCs, the critical threshold for switching between self and other varied with the direction of morphing in AN participants. Finally, when AN subjects were seated in a chair with the backrest and footrest touching their body, the self-recognition threshold (M1) increased significantly, approaching that of controls. Conclusions Although additional research is needed to replicate the results of this preliminary study, it revealed the first behavioural evidence of altered SOD in individuals with AN through an embodied, semiecological face-recognition paradigm. Relationships between body perception and alterations in interpersonal relationships are discussed as well as new research and therapeutic perspectives are presented.