Introduction
Previous experiments have suggested that there is a relationship between level of arousal and behavioral withdrawal in chronic schizophrenic patients (Tizard and Venables, 1957; Venables, 1960). It has also been shown that clinically defined subgroups of chronic schizophrenics differ significantly in degree of social withdrawal (Wing, 1960, 1961). The work to be described was designed to investigate further the relationships between arousal, withdrawal, and clinical condition.Arousal level is a concept which appears to have 2 origins, one psychological and the other physiological. In psychological theory its history may be traced back to such notions as "energy mobilization," Cannon (1915), Duffy (1951), or "behavioral substrate," Freeman (1948). More recently, the close parallel between these ideas and the physiological definition of arousal developing from the work on the reticular system has led to the earlier psychological constructs being subsumed under the heading