Running head: Representing Attachment 1 Representing attachment through meta-analyses: A move to the level of collaboration Carlo Schuengel1, Marije L. Verhage Vrije Universiteit Amsterdam Robbie Duschinsky University of Cambridge Author Note Clinical Child and Family Studies, Faculty of Behavioural and Movement Sciences and Amsterdam Public Health research institute, Vrije Universiteit Amsterdam, The Netherlands Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands, [email protected] Representing Attachment 2 Word count: 2,473 Number of references: 24 Representing Attachment 3 ABSTRACT Generations of researchers have tested and used attachment theory to understand children’s development. To bring coherence in the expansive set of findings, the field early on adopted meta-analysis, with 75 published since 1987. These meta-analyses are increasingly applied in research on disorder and intervention, and in self-report research on attachment anxiety and avoidance in adolescents. However, conventional approaches to meta-analysis have left thorny issues unresolved regarding the intergenerational transmission of individual differences in attachment. We discuss how attachment research has been addressing these challenges by collaborating to pooling data and resources in individual participant data meta- analyses, leading to novel insights and greater theoretical precision. Keywords: attachment, intergenerational effects, meta-analysis, bibliometrics, individual participant data Representing Attachment 4 Representing Attachment: A Move to the Level of Collaboration Attachment is seen in children’s protest and proximity-seeking behavior if they are involuntarily separated from their familiar caregiver. It is also seen in children’s confident exploration of novelty when children perceive that their caregiver is there to protect them from harm (Tottenham, Shapiro, Flannery, Caldera, & Sullivan, in press). Children develop secure attachment relationships with caregivers who are sensitively responsive to the signals and needs of their child, and may develop insecure attachment relationships with caregivers who ignore these needs or respond only intermittently, which contribute to diverging developmental pathways of social functioning and mental health (Ainsworth & Bowlby, 1991). Research on attachment has examined determinants and outcomes of attachment across a broad range of biopsychosocial factors. To summarize the empirical evidence for such links, the field of research on child attachment was an early adopter of meta-analysis. Meta-analysis was called upon to address debates in attachment theory regarding the role of child temperament as an explanation for individual differences (Goldsmith & Alansky, 1987) and the relative species- wide universality of child attachment patterns (Van IJzendoorn & Kroonenberg, 1988). Van IJzendoorn was an especially influential disseminator of the methodology, influenced by Karl Popper’s emphasis on the need for replication as the basis of surety in science (Van IJzendoorn, 1994). Both to provide such surety, and to examine explanations for different outcomes among Representing Attachment 5 studies, meta-analysis became an important instrument to represent empirical evidence and to inform the future direction of attachment research. In 1985, Main, Kaplan, and Cassidy proposed that caregivers’ own state of mind regarding attachment, classified as autonomous (secure), dismissing, preoccupied, or unresolved on the basis of the Adult Attachment Interview, determines the security of children’s attachment relationships by influencing the sensitivity of caregivers’ responses to children. The importance of intergenerational transmission for developmental and clinical psychology lies both in what it can tell us about the contribution of caregivers to their children’s social functioning and mental health, and in what it can tell us about factors that interrupt this contribution. In 1995, Van IJzendoorn published a meta-analytical effect size based on 18 studies of a strength seldom seen in psychological science (r = 0.47/d = 1.06; N = 854), which helped to win acceptance among the research community for Main et al.’s Adult Attachment Interview as a predictor of individual differences in infant-caregiver attachment. However, Van IJzendoorn’s meta-analysis also showed that Main et al.’s model could not fully account for how transmission and non- transmission came about. This finding became known as the ‘transmission gap’ and led to numerous theoretical and empirical efforts to close it (Van IJzendoorn & Bakermans- Kranenburg, 2019). Yet over the years a string of studies, including fairly large ones, also reported null findings for intergenerational transmission. This casted doubt on the replicability of intergenerational transmission, prompting a new meta-analysis. With over four times as much Representing Attachment 6 data as available from 83 samples, Verhage et al. (2016) reported a considerably lower but still relatively strong (Funder & Ozer, in press) effect size (r = .31/d = 0.65; N = 4,102). Studies showed significant heterogeneity in these outcomes, however, which could not be more fully explained without access to finer-grained individual participant data. This paper begins by appraising the scope and impact of meta-analysis on child attachment, which have been important focal points of the field. In the second part of the paper we discuss how individual participant data meta-analysis (Riley, Lambert, & Abo-Zaid, 2010) offers a collaborative model to overcome the limitations of traditional meta-analyses and single studies to further understand intergenerational transmission. META-ANALYSES OF CHILD ATTACHMENT RESEARCH A bibliometric study retrieved all published (up to June 9, 2019) meta-analyses that synthesized descriptives or effect sizes based on attachment assessment with children (up to age 18) and their caregivers across the field of psychology. Full details of the work using Vosviewer (Van Eck & Waltman, 2016) and Bibliometrix (Aria & Cuccurullo, 2017) software can be found in Schuengel, Verhage, and Duschinsky (2019). To date, 75 meta-analyses have been published. Publication rate shows exponential growth up to and including 2018. Also the number of different authors of meta-analyses (often in co-authorship with Van IJzendoorn and Bakermans- Kranenburg) has steadily increased. Representing Attachment 7 Among the meta-analyses are those with aims to test or further specify attachment theory (e.g., testing propositions about the link between parenting and attachment, or between attachment and developmental outcomes), psychometric aims (e.g., reliability and validity of attachment instruments), epidemiological aims (e.g.,describing prevalences across populations), and aims related to understanding intervention (e.g., efficacy of attachment-based interventions). Figure 1 shows cumulative trends over time (1987-2018) in these aims. While the first period reveals an exclusive focus on testing and elaborating attachment theory, from 2004 largely stable proportions can be seen of published meta-analyses with theoretical aims (53%), psychometric aims (8%), epidemiological aims (24%), and aims related to intervention (15%). Representing Attachment 8 Figure 1. Cumulative count of attachment meta-analyses according to main study aim. Reception of Meta-Analyses As of June 9, 2019, the meta-analyses on attachment had been cited in 7,595 publications, growing at an annual rate of 24% per year up to and including 2018. To put this into perspective, the landmark publication by Ainsworth et al. (1978) that initiated empirical attachment research was cited in total 8,641 times, peaking at 480 citations in 2015. Clusters based on machine reading for meaningful terms and phrases in titles and abstracts are shown in Figure 2, based on a cut-off of terms being used in at least 100 papers. Representing Attachment 9 Figure 3 shows the same clusters, with colour gradient indicating average year of the publications from which these terms were drawn. For each of the clusters we provide a brief interpretation. Figure 2. Network clusters of nouns and adjective-noun combinations extracted by natural language processing of titles and abstracts of publications that cited attachment meta- analyses. Representing Attachment 10 Figure 3. Network of nouns and adjective-noun combinations extracted by natural language processing of titles and abstracts by average year of publication citing attachment meta- analyses. The red cluster depicts a network of 34 terms referring to intervention. Besides ‘intervention’, dominant terms include ‘treatment’, ‘program’, ‘practice’, ‘need’, ‘process’, and ‘abuse’. The overlay of publication year of the articles from which these terms were derived indicates increasing interest in this set of topics. Representing Attachment 11 The green cluster depicts a network of 33 terms that reflect the vocabulary that Ainsworth, the founder of attachment research as an empirical paradigm, proposed for describing parent-child relationships. Besides ‘mother’, ‘infant’, and ‘father’, dominant terms are (attachment) ‘security’, ‘responsiveness’, and (maternal) ‘sensitivity’. The overlay of publication year shows, overall, a decrease of attention to the topics in this cluster relative to the other clusters. However, research on sensitivity and on fathers specifically has been increasing among papers citing the meta-analyses, following an opposed trend. The blue cluster depicts a network of 29 items that