The development of hand-mouth coordination in early infancy
The aim of the thesis is to offer a comprehensive account of the developmental course of hand-mouth (HM) coordination from birth until a mature form of the coordination is attained. Questions relating both to the structure and function of the coordination were addressed. Three studies are reported. The method of observation was the same in each case; video records of two perpendicular views of the infant were obtained and a micro-analysis of movement structure was carried out. The main question addressed in study 1 was whether spontaneous HM contacts in newborns are related to hunger. HM contacts were compared before and after feeding in a group of newborn babies. There was no change in the relative distribution of locations of contacts on the mouth and face before and after feeding, but anticipatory mouth opening prior to HM contacts only occurred before feeding. Study 2 sought to obtain detailed measures of transitions taking place between 1-5 months in the structure of HM coordination, and to investigate what factors could be responsible for the changes observed. A longitudinal design was employed where babies were observed at monthly intervals. A small object was placed in the hands of infants to promote oral contacts. At 4 months of age, contacts began to be centred on the mouth (as opposed to other parts of the face) and the frequency of contacts was significantly higher when the object was present relative to the frequency of spontaneous contacts. Anticipatory mouth opening only occurred at 5 months of age, suggesting that this aspect of the coordination follows a U-shaped developmental trajectory. There was evidence that vision was playing a role in motivating HM contacts by 5 months of age. Consistent individual differences between babies were found in different aspects of HM coordination raising the possibility that more than one developmental route is followed in the achievement of mature HM coordination. Study 3 investigated HM coordination cross-sectionally between the ages of 5-9 months. The possibility that the development of reaching was influencing the development of HM coordination was investigated. Two situations were compared, one where the infant had to reach for an object prior to transportation to the mouth and another where the object was placed in the hand of the infant. Although HM coordination and reaching and grasping were already integrated at 5 months, the two coordinations appear to develop independently of each other. The development of HM coordination was found to be marked by motivational and structural shifts and apparent regressions. The results are interpreted within a dynamic systems view of development.