The process of change represents a main, central issue for the study of development. Basic and applied researchers in developmental science have aimed their research work at answering several key questions related to the problem of change. How does change occur? What mechanisms produce change? What conditions are likely to promote the emergence of change in development? Another related question concerns the stability versus instability of new behavioral patterns that emerge as a consequence of an intervention. What are the relationships between variability and stability in developmental processes? Does the emergence of new behavioral patterns tend to suppress the old patterns or to coexist with them? Nevertheless, observing and understanding how change occurs has been recognized to be a quite difficult and challenging task (Miller & Coyle, 1999;Siegler & Crowley, 1991). This is despite recent advances in both theoretical perspectives and methods focused on change processes that have brought considerable progress in the research field (see "Microgenetic designs as promising tools," below). Part of the challenge is due to the complexity of conceptualizing change processes. It is our contention, however, that the main problem appears to come from the difficulty of devising and implementing appropriate methods for studying change while it is occurring (Fogel, 1990;Kuhn, 1995;Siegler, 1995), instead of comparing pre-and post-change behavioral patterns.In this chapter, we aim to illustrate a research design, referred to as microgenetic designs, specifically devised for documenting change processes in development. First, we discuss the limitations of traditional research designs to capture ongoing processes of change. We then present microgenetic designs through an illustration of their key characteristics. This is followed by a review of the theoretical foundations of microgenetic designs as well as some of the historical and current observational and experimental

Weekly laboratory observations of free play for 13 middle-income mother±infant dyads, from 1 to 6 months of age, were used to study the synchronization of developmental trajectories between infant postural position and gaze direction. Mothers sat in a straight-backed chair while holding infants on their laps and were free to adjust the infant's posture. Postural position was coded as upright (supported sitting or standing on the mother's lap) or other (lying, cradling, or being held close to mother). Gaze was coded as either at mother's face or away. The age of onset of visually guided reaching was also assessed. Results show that there were longer durations of gazing away when the infant was in an upright position. Over the 5 month period of observation, the dyads began with a pattern of non-upright positions accompanied by gaze at mother. Contrary to previous predictions, the developmental shift in the first 6 months from exclusive gazing at mother's face to gazing away from mother was not synchronized with the development of reaching, but rather with changes in the infant's posture to more upright positions. The possible role of postural position in fostering positive emotional communication is discussed.Adult ± infant face-to-face play consists of mutual gazing and smiling to achieve a unique form of positive emotional communication in early life (Brazelton,

Oral feeding has been reported to compromise breathing among preterm infants with bronchopulmonary dysplasia (BPD) during hospitalization or shortly after discharge. However, limited information was available concerning whether preterm infants with BPD remain vulnerable to feeding and growth insufficiency after a longer term of follow-up. The purpose of this study was therefore to examine the effect of severity of BPD on pulse oxygen saturation (SpO(2)) during feeding and growth in very low birth weight (VLBW) preterm infants during infancy. Seventy-two preterm infants with VLBW and 15 term infants were prospectively examined their growth and SpO(2) during feeding at 2, 4, and 6 months of corrected age. The severity of BPD was graded in VLBW infants according to the American National Institutes of Health consensus definition. In comparison to VLBW infants with mild BPD and term infants, VLBW infants with severe BPD showed significantly lower mean levels of SpO(2) during feeding at 2-6 months corrected age (P < 0.05). Those with severe BPD further exhibited higher rates of growth delay (weight < 10th percentile) throughout the study period. Among VLBW infants, severe BPD had an adverse relation with subsequent weight measures after adjustment for medical and demographic confounding variables (beta = -904 g, P = 0.03). The consensus BPD definition is useful to identify those preterm infants who are at greater risk of feeding desaturation and growth delay during infancy and close monitoring of SpO(2) during feeding should be advised.

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