The aim of this longitudinal study was to identify family factors that predicted changes in a child's level of behavioural inhibition over time. Behavioural inhibition is defined as a temperamental disposition of children to react consistently to unfamiliar social and non-social events with initial restraint and quiet withdrawal (Garcia-Coll, Kagan, & Reznick, 1984). Although longitudinal research has demonstrated significant stability of behavioural inhibition, this research has also suggested a good degree of inconsistency over time. This study aimed to systematically identify those family factors that may influence a child to become either more inhibited or less inhibited over time.
The model presented in this thesis proposed that parenting style, parental anxiety, parental stressors, and parental social support would have a significant association with changes in a child's level of behavioural inhibition over time. Specifically, it was hypothesised that increased behavioural inhibition would be associated with a parenting style that was less supportive, utilised fewer social facilitation strategies, and was high on criticism and overprotection. It was further hypothesised that parents who manifest higher levels of anxiety would be more likely to demonstrate such a parenting style. Thus, parental anxiety was proposed to have a more distal influence upon child behavioural inhibition. Parental stressors (relationship conflict and negative life events) and social support were also hypothesised to have an influence on parental anxiety, and thus upon parenting style and behavioural inhibition.
In addition to examining family factors that may influence the level of inhibition over time, this study also developed a questionnaire measure of behavioural inhibition. The Behavioural Inhibition Questionnaire, which was found to be reliable and valid, will enable simple, economical, reliable, and valid assessment of inhibition, without the need for costly laboratory-based and naturalistic observational measures. Also developed for use in this research was a questionnaire measure of parenting style. While some of the psychometric properties of the Parenting Questionnaire were relatively low, they were of a similar magnitude to those reported for other measures of parenting style.
The cross-sectional study found that mothers and fathers who were more anxious and who used fewer social facilitation strategies were more likely to have a behaviourally inhibited child. In keeping with hypotheses, mothers and fathers who were anxious tended to use fewer social facilitation strategies, to be less supportive, and to be more critical of their child. However, parenting style was not found to mediate the relationship between parental anxiety and child behavioural inhibition. There was only partial support for the hypothesised effects of family stressor variables on parenting, with higher relationship conflict being associated with less supportive parenting, less use of social facilitation strategies, and more critical parenting for mothers, and with more critical parenting for fathers. For mothers, there was evidence of an interaction (but not moderation) between maternal stressor variables and social support in the prediction of maternal anxiety.
The longitudinal results indicated that children who were behaviourally inhibited at Time 1 were more likely to be inhibited at Time 2. However, there was evidence that approximately 11% of children who had been uninhibited at Time 1 became inhibited at Time 2, and approximately 30-35% of children who had been inhibited at Time 1 became uninhibited at Time 2. The results showed that mothers who used fewer social facilitation strategies at Time 1 tended to have children who became more behaviourally inhibited by Time 2, but this relationship was not found for fathers. Time 1 parental anxiety was associated with Time 2 inhibition, but only through its relationship with Time 1 inhibition and not with the change in inhibition over time. However, there was some evidence that anxious mothers tended to have children who increased in behavioural inhibition over time, but this relationship was not found for fathers.