A historical review of the concepts of self-consciousness is presented, highlighting the important role of the body (particularly, body perception but also body action), and the social other in the construction of self-consciousness. More precisely, body perception, especially intermodal sensory perception including kinesthetic perception, is involved in the construction of a sense of self allowing self-other differentiation. Furthermore, the social other , through very early social and emotional interactions, provides meaning to the infant’s perception and contributes to the development of his/her symbolization capacities. This is a necessary condition for body image representation and awareness of a permanent self in a time-space continuum (invariant over time and space). Self-image recognition impairments in the mirror are also discussed regarding a comprehensive developmental theory of self-consciousness. Then, a neuropsychological and neurophysiological approach to self-consciousness reviews the role of complex brain activation/integration pathways and the mirror neuron system in self-consciousness. Finally, this article offers new perspectives on self-consciousness evaluation using a double mirror paradigm to study self- and other- image and body recognition.

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.

Our aim in this study was to affirm or negate (quantitatively) our subjective impression of altered hands and knees crawling (H&K crawling) among children with Autism Spectrum Disorder (ASD). Through parental questionnaires and children’s health records, we retrospectively compared early motor skills, including the frequency of H&K crawling in 79 children with Autistic Disorder or Asperger Syndrome versus 100 children with typical development (TD). We found H&K crawling to be significantly less frequent among children with ASD (44.2%) versus children with TD (69%). Children with ASD also showed a decreased frequency of acquiring a seating position without help and a later mean walking age compared to the TD children. These data suggest that early motor development delays may be a useful sign for detecting ASD at early ages.

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.

Background Self/other distinction (SOD), which refers to the ability to distinguish one’s own body, actions, and mental representations from those of others, is an essential skill for effective social interaction. A large body of clinical evidence suggests that disruptions in SOD may be key to social communication deficits in individuals with autism spectrum disorders (ASD). In particular, egocentric biases have been found in cognitive, affective, behavioural, and motor domains. However, research in this area is scarce and consists of recognition paradigms that have used only static images; these methods may be insufficient for assessing SOD, given the increasing role of embodiment in our understanding of the pathophysiology of ASD. Method A single-centre, prospective pilot study was carried out to investigate, for the first time, self-recognition and SOD in seven adolescents with ASD compared with matched, typically developing controls (TDCs) using the "Alter Ego"TM double mirror paradigm. The participants viewed a double mirror in which their own face was gradually morphed into the face of an unfamiliar other (self-to-other sequence) or vice versa (other-to-self sequence); participants were instructed to indicate at which point the morph looked more like their own face than the other’s face. Two judgement criteria were used: 1) M1: the threshold at which subjects started to recognize their own face during the other-to-self morphing sequence; 2) M2: the threshold at which subjects started to recognize the other’s face during the self-to-other morphing sequence. Results Consistent with the predictions, the results showed that the participants with ASD exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence, suggesting an egocentric bias. SOD impairments were also marginally correlated with ASD severity, indicating earlier face recognition in more severely affected individuals. Furthermore, in contrast with that of TDCs, the critical threshold for switching between self and other varied with the direction of morphing in ASD participants. Finally, these differences in face recognition and SOD using mirrors, unlike previous research using static images, support the central place of bodily self-consciousness in SOD impairments. Conclusions Although additional research is needed to replicate the results of this preliminary study, it revealed the first behavioural evidence of altered SOD in ASD individuals on an embodied, semiecological face-recognition paradigm. Implications for understanding ASD are discussed from a developmental perspective, and new research and therapeutic perspectives are presented.