The relationship between twins is based on primitive mechanisms which need to be mitigated by a containing and processing mother for adequate emotional development to take place. Where this fails, the twins remain in an arrested state of development dependent on splitting and excessive projective identification, and unable to separate. This is reflected in the transference relationship, the psychotherapist being experienced as a twin, a reflection of the patient, rather than as a container. Through intervention in the twinship via interpretation of the transference relationship, the patient may be enabled to find the psychotherapist as a processing mother and to develop a sense of self, a separate identity.