Opportunity sample of 88 children was selected from the clinic where Bowlby worked. 44 were juvenile thieves who had been referred to him because of their stealing. Bowlby selected another group of 44 children to act as controls. They had their IQ tested by a psychologist who assessed their emotional attitudes toward the test. The groups were matched for age and IQ. The children and their parents were interviewed about early life by Bowlby, a psychologist, and a social worker. The psychiatrist, psychologist, and social worker made separate reports.