1. Amorosa H (to be published) Disorders of vocal signalling in children. In: Papoušek H, Jürgens U, Papoušek M (eds) Nonverbal vocal communication: comparative and developmental approaches. Cambridge University Press, Cambridge
2. Bornstein MH, Ruddy M (1984) Infant attention and maternal stimulation: prediction of cognitive and linguistic development in singletons and twins. In: Bouma H, Bouwhuis E (eds) Attention and performance. Erlbaum, London, pp 433–445
3. Chevalier-Skolnikoff S (1982) A cognitive analysis of facial behavior in Old World monkeys, apes, and human beings. In: Snowdon CT, Brown CH, Petersen MR (eds) Primate communication. Cambridge University Press, Cambridge, pp 303–368
4. Darwin C (1871) The descent of man. Murray, London
5. Demany L (1982) Auditory stream segregation in infancy. Infant Behav. Develop 5: 261–276