Previous studies found that mirror-gazing at the subject's reflected own face, under a low illumination level, produces acute dissociation. In the present study, a split-mirror was used, which divides the subject's reflected face vertically into two half-faces, and dissociative states were compared to single-mirror gazing. Twelve healthy naïve individuals, who were sampled from students of an Art Academy, volunteered in a within-subject experiment. Dissociative states were measured through a 9-item self-report questionnaire on three scales: illusions of face deformation (derealization); illusions of body detachment (depersonalization); illusions of different self-identity (dissociated identity). Results showed that split-mirror gazing increased dissociation with respect to single-mirror gazing. Illusions of different self-identity, such as double-identity (i.e., left-identity versus right-identity) or double-personality, increased during split-mirror gazing with respect to single-mirror gazing, whereas illusions of face deformation and body detachment were unchanged. Findings support the distinction between detachment and compartmentalization, and may provide a tool for experimental investigation of dissociative identity disorder (DID). Finally, the students' portraits illustrated illusions of self-identity in split-mirror gazing: left-identity (portrayed in the right side of drawings) displayed illusions of more negative personalities and/or emotions, while right-identity (portrayed in the left side) showed more positive features.
Keywords: Compartmentalization; detachment; dissociation; face; identity; mirror; self.