Emotion-related behaviors in infants : a longitudinal study of patterns and variability

Central to this thesis is the question whether age-determined periods of emotional instability can be observed in normally developing infants. From a developmental psychobiological perspective, it is unlikely that there is a strictly timed universal pattern of periods of characteristic infant behavior, especially if this behavior is related to emotions and motherinfant interaction. To presuppose the existence of such a pattern would amount to leave aside each infant's developmental status, history and temperament, and such influential environmental and family factors as maternal personality and caregiving style. Nonetheless, a study by Van de Rijt-Plooij and Plooij (1992a) reported findings of a universal pattern of 10 strictly timed periods characterised by infant emotional instability and increased motherinfant body contact. The goal of this thesis thesis is twofold. First of all, to report the results of attempts to validate the findings of Van de Rijt-Plooij & Plooij (1992a), which presuppose low interindividual variability in the display of emotion-related behaviors. Second, to investigate the opposite idea of high inter- and also intra-individual variability in these behaviors (which goes against the concept of universal age-related periods of emotional instability). In doing so, a closer inspection of the issues of variability, stability and patterns in emotion-related behaviors in infancy is obtained.