The smiling and related responses in early human infancy : an experimental and theoretical study of their course and significance.
In this thesis a study is made of the organisation and
biological significance of the smiling response in early hu~an
infancy. It is based in part on the results of previous
empirical studies of smiling, the relevant evidence from which
is syste~atizedanj critically exacined, and in part on
exploratory experiments carried out by the writer in a pilot
study of infants in the first eight months of life.
The mode of development of the response over this period
is examined, taking account of the detailed variations in its
characteristics as it occurs in association with other behaviour
in various types of situation. The changing nature of the
external and internal factors that control it is traced. The
trenJ of increasing limitation of occurrence of the response to
situations of social interaction, first with other people in
general and then with particular individuals, especially the
@other-figure, is elaborated. In relation to this trend the
effects of processes of hlaturation and learning on the development
of the mechanism that subservos the response arc considered.
Viewing the trend in the perspective of evidence from
stUdies of the development of early social relations in a variety
of classes of animal, the role of the response as a means of
social communication, and its biological function in contributing
to the development of the infant's attachment to his mother ~re
worked out. This function is further elaborated by consideration of the descriptive, causal and functional relations of smiling
both with the responses of laughing and crying and with
homologous responses at other primate levels. Such comparative
study leads also to a hypothesis about the derivation of smiling
as a greeting response from smiling as low-intensity laughing.
The ontogeny of the greeting response is seen as the natural
outcome of trends discerned in the evolution of the infant mother