Bridging the theory to evidence gap: a systematic review and analysis of individual × environment models of child development

Abstract

A key theoretical principle of developmental psychology is that the response of individuals to developmental experiences can vary. This principle is exemplified in theoretical models of individual × environment interactions, including diathesis stress, differential susceptivity (biological sensitivity to context), and vantage sensitivity.Despite a theoretical underpinning and growing empirical base, there is considerable variability in evidence for these theoretical interactions and the literature has not always delivered well with definitive findings towards the provision of evidence-based interventions tailored to meet the needs of individual children.This thesis has therefore focused on understanding and bridging the gap between theory and evidence for specific individual × environment explanatory models of child behavioural outcomes. It examined the theory and evidence for moderation of parenting effects by child reactivity using a strategy of targeted review and empirical analysis. The thesis aimed to 1) systematically analyse the current literature to identify any patterns in the use of measurement and methods of analysis that might direct future research into individual × environment models. And, 2) conduct analyses using existing data (Longitudinal Study of Australian Children, Family Life Project) to explore effects of different measurements on individual × environment models; systematically examining effects of different measures of parenting, behavioural outcomes, and reactivity. A diagrammatic outline of the thesis is provided in Figure 1.Findings from both the systematic review and empirical analyses revealed that the gap between theory and evidence is extensive. A review of 542 individual × parenting interactions found that 86 were described as statistically reliable. However, within- and between-studies, these reliable interactions inconsistently supported different theoretical models and sporadically varied with measures of parenting, behaviour, and individual characteristics.Two empirical analysis chapters confirmed these inconsistencies. The first empirical study examined the interaction between parent-reported parenting (warmth and harshness) and parent-reported temperament (persistence, introversion, reactivity, difficult composite) predicting parent and teacher reported behavioural outcomes (internalizing, externalizing, pro-social) in a longitudinal sample of 1289 Australian children at ages 4 and 6, and across ages 4, 6, and 8. By transparently examining the full matrix of analytical decisions, the results showed that 13 (2.5%) of 512 interactions were statistically reliable and that temperament moderated the effects of parenting on behaviour. However, these reliable interactions did not consistently support a theoretical model and varied with measures of parenting, temperament, and behaviour, the age of the child, and the reporter of behaviour.The second empirical chapter extended this analysis by considering four additional measurements and examining an additional data set of children from the United States of America. Specifically, the analysis examined interactions between parent-reported parenting at 2 years (warmth, hostile) and parent-reported temperament at 1 year (approach, cooperation, irritability, difficult composite) predicting parent reported behaviour at 4 years (internalizing, externalizing, pro-social) using a longitudinal sample of 3062 Australian children. Additionally, the analysis explored interactions between observed parenting at 15 months and 2 years (sensitive composite, negative-intrusive composite, positive regard, negative regard, sensitivity, animation, stimulation, detachment, intrusiveness) and parent-reported temperament at 6 months (fear, distress to limitations, falling reactivity, negative affectivity composite, duration of orienting, approach) predicting parent reported behaviour at 3 years (social and emotional competence, internalizing, externalizing, pro-social) using a longitudinal sample of 1093 children from the United States of America. Utilising a transparent analytical approach, the results found 2 (3%) of 64 interactions were statistically reliable in the Australian sample, whilst there were no statistically reliable interactions (of 1620) in the sample from the United States of America. As with the earlier chapter, the two statistically reliable interactions supported different theoretical models and there was no consistency in interaction effects across measures of temperament, behaviour, or parenting. Thus, in total, these results and the systematic review demonstrate that theory and evidence do not consistently align for individual × environment models of development.To better align theory and evidence for individual × environment models, the thesis concludes with several suggestions for future research and an integrative discussion of the results. Suggestions for future research include a detailed focus on measurement, extensive validation and exploration of analytical decisions, the use of optimum and more causal research designs to elucidate interaction effects, the use of simulation studies to understand the implications of design, and critically assessing and accurately portraying results.Individual × environment interactions remain a key principle of developmental psychology. Though this thesis has demonstrated a gap between theory and evidence, improvement in research design and measurement may align theory with evidence and yield insights that can assist the behavioural development of children.