This is an account of the Symposium Bel-Air II, held at Geneva in September 1964. The account is in three parts—experimental, clinical, and discussions—preceded by a brief historical sketch, calling especial attention to the work of Condillac, Rousseau, Linné, Malson, and Itard, concerning savage infants and especially the experiments of Frederic II on human infants reared in isolation. The scientific study begins with the work of Spitz in 1945. Since 1954 Hebb and others have undertaken experiments to study what one calls sensory isolation.
The experimental session began with a long study of how the nervous system habituates itself to sensory stimulation. Two types of habituation are distinguished, specific and nonspecific. The former type is the diminution and final disappearance of responses to afferent stimulation which is not significant to the organism; the latter is represented by habituation to the reaction of awakening or of orientation.