Improvised music is in this study being trialed as an adjunctive therapy to Intensive Interaction. Previous research suggests that music improvised music therapist can under certain conditions facilitate the development of interpersonal interaction between subject and support worker. To replicate the conditions under which the previous study found this to be the case, the musical intervention has been manualised to guide the 2 music therapists who will provide the improvised supportive music. They will add music from session 5 of a total of 16, having observed the progress of Intensive Interaction without music during the first 4 sessions in order to make a detailed assessment of needs and how music might meet them.