Research figure: Mary Ainsworth · Written by Artificial Sapiens
Mary Ainsworth’s Uganda study was a naturalistic investigation of the development of infant–caregiver attachment conducted during 1954–1955 among Ganda families in communities near Kampala. Through repeated home visits and detailed descriptions of everyday interactions, Ainsworth examined how infants came to distinguish familiar caregivers, seek proximity when distressed, and explore their surroundings while keeping those caregivers available. The study supplied some of the first systematic developmental observations through which attachment theory could be evaluated in actual relationships. Its historical record culminated in Ainsworth’s 1967 volume, Infancy in Uganda: Infant Care and the Growth of Love. This article focuses specifically on the 1950s fieldwork, the questions it examined, the research design, the behavioral findings, and the limits of interpreting them. The Yale eHRAF record of the original book and Waters and colleagues’ 2026 reappraisal provide essential historical anchors.
Origins of the Research Question
The investigation arose from a formative period in developmental psychology when researchers were trying to explain the infant’s special relationship to familiar people. John Bowlby was developing attachment theory with attention to separation, proximity seeking, and the evolutionary and developmental significance of caregiver availability. Ainsworth had collaborated with Bowlby at the Tavistock Clinic in London. Her earlier intellectual training at the University of Toronto under William E. Blatz also gave the concept of security a central place in her thinking. Blatz’s security theory and Bowlby’s attachment theory were historically distinct contributions. Ainsworth developed observational concepts and methods through which aspects of these ideas could be studied as developing patterns of behavior. Duschinsky’s historical reconstruction situates the fieldwork within these intellectual relationships.
The central research challenge was to distinguish a continuing relational organization from isolated infant reactions. A child might cry when uncomfortable, follow an adult, become interested in a stranger, or return to play after being comforted. Each observation is meaningful only in relation to the participants, circumstances, age, and sequence of events. What counted as attachment? How did infants develop preferences for particular caregivers? How did interactions differ across families? Could security help explain when an infant confidently explored and when the infant sought comfort? Uganda offered an opportunity to follow these questions through repeated observations rather than one-time reports about maternal affection.
Ainsworth’s program therefore treated attachment as a developmental phenomenon that unfolds across situations. The goal was not to assign a timeless personality label to an infant, but to document recognizable patterns in how an infant oriented toward and interacted with familiar people. That question was well suited to intensive observation: the meaning of repeated proximity seeking, comfort, and exploration becomes clearer as the investigator sees the same relationship in several ordinary circumstances.
Cultural and Historical Setting
The study took place in the British Uganda Protectorate, before Ugandan independence in 1962. The participating families were Ganda, also called Baganda, living in rural localities near Kampala. The designation matters for scientific generalization. These observations were gathered among particular families within a distinct regional, linguistic, social, and colonial context. They are not a representative survey of Uganda, and they should not be presented as an unrestricted description of African caregiving.
Ainsworth’s observations occurred in households where mothers and other caretakers could participate in infant care. Routines of feeding, play, rest, illness, household work, and movement between family members formed the background of the study. An infant’s approach to a familiar person acquired meaning within these routines. Opportunities for exploring objects or moving away from a caregiver also depended on infant age and the physical and social environment. Naturalistic observation made it possible to see such connections, while also requiring substantial interpretive care.
The geographical description is reported somewhat differently in historical sources. The Yale eHRAF catalog summarizes twenty-three households across seven villages about fifteen miles outside Kampala. A later history by Duschinsky summarizes the work with a different village count. These sources may reflect different conventions for counting the sites involved. A precise scholarly account records that discrepancy rather than treating every later summary as identical.
The colonial research setting introduces questions about access, interpretation, and power. Participation by Ganda families, assistance from a local English-speaking Ganda social worker and interpreter, and relationships established through local clinical contacts were integral to the production of observations. Ainsworth’s conceptual vocabulary was shaped by North American and British psychology. The behaviors she observed belonged to a social world with its own histories and understandings of children. A contemporary evaluation must recognize both realities when deciding what the field notes establish.
Sample: Infants, Mothers, and Households
The study is commonly described as involving twenty-eight infants from twenty-six mothers or families, including two pairs of twins. The Yale eHRAF description identifies twenty-three participating households. Those counts are not interchangeable. One number refers to infants, another to maternal relationships or participating families, and another to residences. A sample of twenty-eight infants is therefore consistent with a smaller number of household settings. Ainsworth’s primary bibliographic record and Bretherton’s historical review are useful for tracking the distinctions.
The participating infants entered the observations at differing developmental stages. The Yale catalog describes starting ages ranging from two days to eighty weeks. This breadth matters methodologically: a newborn has limited locomotion and different forms of communication from an older infant able to crawl, walk, reach toward people, and explore objects. An apparent contrast between two infants may reflect age, opportunity, context, or a developing relationship. The fieldwork could examine developmental variation, but it did not equalize every child’s age or length of follow-up.
Sampling was geographically localized and depended on practical access to families. The observations were suited to detailed case analysis, not population estimation. Results cannot provide a defensible prevalence rate for attachment types among all Ganda infants. Nor can they establish the worldwide distribution of attachment patterns. These limits are features of the research design and of the inferential claims it can support.
Fieldwork Procedure and Research Design
Repeated home visits
Ainsworth’s primary procedure was to visit participating families repeatedly and observe infants within their ordinary domestic environments. Historical reconstructions describe visits of approximately two hours, often twice monthly, with attention to infant behavior, caregiving responses, family routines, and developmental change. The Yale eHRAF description refers to seven months of participant observation. Bretherton (2013) and other historical accounts describe a field research period of approximately nine months. The difference can reflect the interval counted as intensive observation versus the broader field program, and the exact exposure of every infant need not have been identical.
Repeated visits provided access to events that could not be guaranteed in a laboratory appointment. A baby might become tired, react to someone entering, move toward a familiar person, seek contact while upset, be soothed, and then begin exploring again. The investigator could compare such sequences across occasions. What made these events useful was their temporal organization: the behaviors occurred in relation to particular people and circumstances rather than as disconnected scores.
Field notes and behavioral description
The observations relied on detailed records describing what infants and caregivers did. The historical account emphasizes the process of translating immediate observations into organized written notes. Ainsworth’s attention included proximity, crying, gestures, following, orientation toward adults, contact seeking, and changes in play or exploration. These observations supported comparisons within an individual child’s development and across relationships. Bretherton’s 2013 analysis clarifies how the field procedures later influenced more formal assessments of sensitivity.
In naturalistic research, a note such as “the baby cried” conveys far less than a record identifying who was present, what had happened beforehand, whether the caregiver responded, how the child reacted to the response, and what occurred next. Behavior must be interpreted within the sequence. A response that looks like avoidance in one situation may reflect fatigue or diverted attention in another. The usefulness of detailed field notes lies partly in their ability to preserve this context.
Interpreter and clinic involvement
A local English-speaking Ganda social worker and interpreter assisted the field investigation, and local clinic contacts formed part of the recruitment and developmental-information setting. The contribution of local participants was essential. Translation can also shape data: when descriptions of family routines or the meaning of a behavior move between languages, the investigator and interpreter make decisions about wording, relevance, and interpretation. Contemporary scholarship considers that an important methodological consideration rather than a merely logistical detail.
Clinic-derived developmental information and direct home observations have different epistemic roles. A developmental measure offers a standardized or semi-standardized snapshot of certain capacities; observation of everyday interaction reveals how capacities are enacted amid familiar relationships. Combining information can enrich case interpretation, but it does not make a small observational study a randomized experiment or guarantee independent measurement across every case.
Observational rather than experimental inference
No caregiver was randomly assigned a level of responsiveness, and no infant was randomly assigned a family environment. The Uganda study was not a controlled intervention trial. Its central analytic resources were longitudinal description, case comparisons, and interpretation of observed relational sequences. It could generate hypotheses about security and caregiving while leaving causal direction open. A child’s temperament, health, developmental stage, and household circumstances could affect both the infant’s signals and adult behavior. Such reciprocal processes should remain part of the explanation.
The fieldwork also preceded the Strange Situation Procedure. The standardized laboratory separation and reunion episodes were subsequently developed through Ainsworth’s Baltimore research, not administered to the Ganda cohort as though they were part of the original 1954–1955 protocol. Duschinsky (2020) reconstructs this historical progression.
Development of Selective Attachment
A central observation concerned the growing differentiation of familiar people from other people. Infants increasingly recognized and preferred particular caregivers in ways visible in behavior. They oriented toward familiar people, monitored their whereabouts, sought contact, followed them when mobile, and responded to separations or reunions in context-dependent ways. These tendencies mattered when they formed recurrent patterns across occasions. An isolated movement toward an adult does not by itself demonstrate a settled attachment relationship.
Attachment development was viewed in relation to age and experience. Infants acquired new motor capacities, had more opportunities to initiate proximity, and participated in repeated interactions that could alter their expectations about caregiver availability. The developing preference for a familiar caregiver was a relational achievement that researchers could observe over time, rather than an inference drawn from a questionnaire about the adult’s feelings.
The field evidence also helped refine the contrast between having contact with a familiar person and using that person when a need arose. Comfort after distress and resumed engagement with surroundings were especially informative sequences. They suggested that attachment organization should be studied through changing behavior under different conditions, with attention to the role of the caregiver’s response.
Distress, Contact, and Comfort
An infant’s behavior during distress can make the significance of a familiar relationship more visible. Crying, reaching, following, resistance to separation, and settling after contact may indicate that the caregiver has a special role. Yet the frequency or intensity of distress must be interpreted carefully. Illness, hunger, unfamiliarity, fatigue, and temperament all affect crying and approach. High protest is not synonymous with insecurity; low protest is not evidence that the child lacks a relationship.
What matters is the coordination of signals and responses. An infant may signal a need, obtain comfort, and return to play. Another sequence might show continuing distress despite an adult’s presence. Interpretation depends on the history of interactions, the immediate situation, the caregiver’s actions, and the child’s subsequent behavior. This process-based approach was a lasting methodological lesson of the Ugandan case material.
Exploration and the Origins of Secure-Base Behavior
Ainsworth’s observations made the relationship between attachment and exploration a major developmental question. Infants could engage with objects, other children, and surroundings while maintaining an orientation toward a familiar adult. A caregiver’s accessibility might allow an infant to investigate with more confidence, and the infant could renew proximity or seek help as circumstances changed. This pattern helped develop the idea of the caregiver as a secure base for exploration.
Secure-base behavior is defined by organized use of the relationship, rather than by a fixed physical distance. An infant who stays near a caregiver in an unfamiliar setting might be adapting appropriately to uncertainty. Another infant who moves away to play may still monitor the caregiver and return for reassurance. Understanding security requires observation of the relation between exploration, proximity seeking, distress, and recovery. Waters, Vaughn, Bretherton, van Rosmalen, and Marvin (2026) identify that integration as a continuing contribution of the original Uganda research.
This perspective linked a broad theoretical idea to observable interaction. Security became an aspect of the organization of the infant–caregiver relationship rather than a loose synonym for affection, low anxiety, or willingness to explore. Later research refined the definition and established new measurement procedures; the Uganda material shows its observational formation.
Individual Differences and Early Descriptive Groupings
The Uganda cases varied in how infants displayed attachment-related behavior and used caregivers during distress or exploration. Some historical accounts summarize Ainsworth’s provisional descriptions as sixteen secure, seven insecure, and five labeled nonattached in the period’s terminology. These figures are an exploratory classification of a small historical case collection. They should not be equated with the later Strange Situation A/B/C categories. Neither should they be used to derive national prevalence or to identify clinical disorders. Duschinsky’s historical account explains how early descriptions evolved into later operationalized categories.
The old label nonattached deserves especially careful handling. It reflects what the observer identified under the early coding framework and within the available observation period. It does not establish the absence of affection or social bonds, nor does it justify applying a contemporary diagnosis. Infants differed in developmental age and in opportunities to reveal the behaviors being observed. Historical classification vocabulary must be read as part of the development of an empirical research program.
The scientific significance of the groupings lies less in their numerical distribution than in the possibility of describing systematic differences across relational histories. They directed attention to questions of organization, caregiver responsiveness, and how to observe the same psychological phenomenon with greater reliability.
Caregiving Responsiveness and Sensitivity
Ainsworth’s field observations helped shape her later concept of maternal sensitivity, a historical term for an observational construct now also studied with fathers and other caregivers. Sensitive response involves noticing an infant’s signals, interpreting them reasonably accurately, and responding promptly and appropriately to the infant’s state. These elements concern the sequence of actual interaction rather than a global judgment about whether a caregiver is a good person.
The Uganda material drew attention to variations in adults’ responsiveness and the ways infants responded to familiar people. A caregiver might recognize emerging distress, respond to a request for contact, and then permit the infant to resume exploration. Another interaction might involve missed signals or responses poorly matched to the child’s needs. These sequences made responsiveness an observable research question. Bretherton’s historical review documents the relation between early fieldwork and Ainsworth’s later sensitivity measures.
An observational association between responsiveness and infant behavior does not establish that sensitivity is the sole determinant of security. Infant characteristics, illness, family circumstances, social support, and competing demands also influence interaction. Moreover, caregiving can involve several adults. Historical maternal language should not narrow the science to an assumption that only mothers provide attachment relationships.
The Intellectual Sequence: Blatz, Bowlby, and Ainsworth
William E. Blatz’s security theory formed part of Ainsworth’s early psychology training. John Bowlby formulated the central theoretical architecture of attachment, including its developmental and separation-related concerns. Ainsworth’s contribution was to turn major elements of this intellectual framework into detailed questions about observable infant behavior and caregiving conditions. She also developed concepts through the surprises and patterns encountered in the field. Intellectual ownership should be attributed with this historical sequence intact.
Ainsworth’s Uganda observations supplied descriptive evidence bearing upon Bowlby’s emerging theoretical propositions while also broadening the analysis of attachment beyond overt separation distress. Exploration, caregiver accessibility, and individual differences became central. The subsequently developed laboratory procedure and the Baltimore longitudinal work were methodological extensions, not descriptions of what happened in the Ugandan homes. Duschinsky (2020) provides a detailed history of this progression.
From Uganda to the Baltimore Research Program
Following the Uganda work, Ainsworth established an intensive longitudinal observational program in Baltimore in the 1960s. It brought a different sample and more systematic measurement to questions that Uganda had helped formulate. The Strange Situation Procedure was developed within that later research trajectory as a standardized series of laboratory episodes emphasizing separation, reunion, proximity seeking, and exploration.
Ainsworth and Barbara A. Wittig jointly authored the important 1969 methodological chapter. Ainsworth and Silvia M. Bell subsequently published research on attachment, exploration, and separation. The original 1978 Patterns of Attachment monograph credited Mary D. Salter Ainsworth, Mary C. Blehar, Everett Waters, and Sally Wall. The A/B/C classification framework described secure, avoidant, and resistant or ambivalent patterns in the later laboratory research tradition. The four-author monograph is a primary source for that distinct scientific stage.
Mary Main and Judith Solomon subsequently introduced and elaborated the disorganized/disoriented D category. It must be attributed to their later work. Neither the Uganda field notes nor Ainsworth’s original A/B/C categories contain the later D category. Adult romantic attachment questionnaires and models likewise arose through a separate later research literature. These conceptual boundaries matter because different instruments and settings assess different phenomena.
Strengths of the Naturalistic Method
Repeated observation allowed Ainsworth to follow a developing relationship in context. This longitudinal depth made it possible to connect behavior across time instead of interpreting a single episode in isolation. The approach supported discovery of patterns whose importance might not have been anticipated at the start of the study. Field notes captured routines, social interactions, and event sequences that standardized questionnaires often miss.
Observing behavior in familiar surroundings gave the study ecological richness. Children’s distress, comfort, and exploration appeared within actual household routines rather than only in an artificial experimental task. This made the work especially valuable for theory development. Researchers could ask what attachment behavior looked like in everyday conditions before designing more formal assessments.
The detail of individual cases also preserved developmental diversity. Children were not treated as interchangeable data points. Differences in age, mobility, family participation, and current circumstances could be considered when interpreting behavior. These strengths are characteristic of careful observational inquiry and remain relevant to modern mixed-method and ethnographic developmental research.
Limits of the Evidence
Small, localized sample
Twenty-eight infants across a limited number of households are sufficient to illustrate relational phenomena, but not to establish population prevalence or narrow statistical uncertainty. Family access was practical rather than probability-based. The findings should therefore not be generalized mechanically to the Ganda population, all Ugandan infants, or all cultures.
Age, observation length, and developmental heterogeneity
The infants entered the investigation at different ages and were observed during an interval when rapid developmental change affects mobility, signaling, stranger responsiveness, and exploration. These differences can complicate comparisons. A behavior absent from a brief observation may be developmentally unavailable or simply unobserved. Longer and standardized follow-up would help distinguish such possibilities.
Observer, translation, and coding effects
Naturalistic records involve decisions about what to notice, how to document it, and which psychological meaning to infer. Ainsworth’s interpretation was informed by prior theories and mediated in part through an interpreter. Contemporary standards would require greater transparency about coding rules, independent ratings, linguistic mediation, and reliability when converting case descriptions into quantitative categories. These concerns call for careful historical interpretation rather than dismissing the descriptive evidence.
Causal ambiguity
The design was observational. Responsiveness and attachment-related behavior developed together within shared family circumstances. A correlation between them cannot prove that one alone caused the other. Child temperament, health, environmental adversity, social support, and caregiver opportunities can each influence the observed sequence. Testing mechanisms requires additional designs, replication, and converging evidence.
Cultural and colonial interpretive limits
The local social setting determined how caregivers were available and which infant behaviors could be observed. Colonial power relations and outsider assumptions could shape participant recruitment, communication, and the selection of explanatory categories. A contemporary researcher must avoid interpreting unfamiliar caregiving arrangements as deficiencies merely because they differ from practices used to construct Western measures. The research remains historically significant when these limits are openly included in its evaluation.
Contemporary Evidence on Sensitivity and Attachment
Modern evidence provides an independent way to evaluate ideas that the Uganda work helped make observable. A 2024 meta-analysis by Sheri Madigan and colleagues combined 174 samples involving 22,914 parent–child dyads. It found a pooled association between caregiver sensitivity and attachment security of r = .25, with a 95% confidence interval of .22 to .28. This is a modest positive association and indicates that responsiveness is related to security while substantial variation remains unexplained.
The synthesis reported associations for maternal sensitivity of r = .26 and paternal sensitivity of r = .21. The findings support investigation of responsive caregiving across different caregivers, with attention to variations in methods and samples. Researchers also found that assessment choice, duration of observation, measurement reliability, and the time between assessments influenced estimated associations. These findings underscore the importance of Ainsworth’s observational questions without treating her fieldwork as a modern meta-analysis or a controlled causal experiment.
A separate 2023 meta-analysis of more than 20,000 Strange Situation procedures studied results in the later laboratory tradition. Its aggregate findings concern the later measurement system and the body of work that developed after the Uganda study. They should not be presented as outcomes measured in the 1954–1955 field sample. The distinction between an original exploratory investigation and evidence from subsequent research is essential to an accurate scientific history.
The 2026 Scholarly Reappraisal
An October 2026 article by Everett Waters, Brian E. Vaughn, Inge Bretherton, Lenny van Rosmalen, and Robert S. Marvin revisited Infancy in Uganda in light of decades of later attachment research. Its emphasis fell on the organization of infant behavior in relational sequences, the interdependence of attachment and exploration, and the refinement of security as a concept distinct from bond strength or general comfort. The 2026 article and its bibliographic record provide contemporary scholarly context for reading the original observational work.
This reappraisal is an interpretation of the classic study, not an independent replication involving the historical infants. It can clarify the questions Ainsworth introduced and the directions later research took, while empirical claims about associations and generalizability must continue to rest on the methods and samples that test them.
Established, Limited, and Contested Conclusions
The established historical conclusions include the 1954–1955 field investigation near Kampala, the small Ganda infant sample, repeated observations within households, and the 1967 publication that preserved the research. The evidence supports the claim that Ainsworth used these cases to develop observational understandings of selective attachment, proximity seeking, secure-base behavior, and caregiving responsiveness.
Established contemporary evidence includes a modest average positive association between caregiver sensitivity and attachment security across independent subsequent studies. The magnitude of the association and its methodological variability are important parts of that conclusion.
Limited conclusions concern exact frequency estimates and causal mechanisms within the original Uganda sample. The cohort and observational procedures were designed for detailed developmental description, not statistical representativeness or manipulation of caregiving conditions.
Contested questions concern how culturally distinct practices affect the interpretation of attachment-related behaviors, how much particular research assessments generalize across social contexts, and whether early classifications have sometimes been overextended into predictions about personality or clinical diagnoses. These questions require methods suited to their scope and should not be settled through the Uganda case counts alone.
Scientific Legacy of the Uganda Fieldwork
The Uganda study showed how attachment could become an empirical object of developmental science through detailed behavioral observations. It connected the study of comfort and proximity with the study of exploration, developmental change, and caregiver responsiveness. Its central methodological lesson was that relational behavior requires attention to sequence, context, and the history of interaction.
The work also demonstrates why theoretical contribution and methodological authorship deserve precise attribution. Bowlby provided the attachment-theoretical framework. Ainsworth brought distinctive observational and conceptual innovations, which she developed further in Baltimore. Wittig, Bell, Blehar, Waters, Wall, Main, and Solomon made historically specific contributions at later stages. The Uganda study is a foundational chapter in that cumulative scientific history.
The fieldwork’s contemporary importance lies partly in its remaining questions. Scientists must establish which behaviors indicate organized attachment, how caregiver responses shape developmental trajectories, what cultural settings permit researchers to observe, and how assessment methods influence results. Ainsworth’s small, context-rich study helped articulate these problems in a way that later research could test more rigorously.
Frequently Asked Questions
When did Mary Ainsworth study infants in Uganda?
She conducted the field investigation in 1954–1955 among Ganda families near Kampala. Historical accounts distinguish approximately seven months of participant observation from a broader period of field research. The original book reporting the work was published in 1967.
How many children participated?
Twenty-eight infants participated. Historical descriptions also refer to twenty-six mothers or families and twenty-three households. These are counts of different units, not three competing estimates of the number of infants.
What did she discover?
She documented developing patterns of selective relationships with familiar caregivers and the coordination of contact seeking, distress, comfort, and exploration. The fieldwork helped clarify attachment security and the importance of caregiver responsiveness.
Was the Strange Situation used in Uganda?
No. The standardized Strange Situation Procedure was developed later in Ainsworth’s Baltimore research. The Uganda study used repeated naturalistic observation of family life.
Did this study prove that maternal sensitivity causes secure attachment?
The observations suggested important links between responsiveness and infant behavior, but the design was not a causal experiment. Modern research finds a modest positive association across many independent samples and caregivers.
Can the early Uganda groupings diagnose an attachment disorder?
No. The period-specific descriptive groupings were exploratory observations of a small cohort. They were not modern clinical diagnoses, and they are distinct from the later standardized Strange Situation classifications.
Related Articles
Mary Ainsworth — The central scientific and biographical account of Ainsworth’s career, major theories, research methods, collaborators, and original publications.
Attachment in Infancy and Early Childhood: Security and Development — The broader developmental research on infant attachment and caregiving beyond this single historical field study.
Mary Ainsworth's Infancy in Uganda: The 1967 Study and Its Legacy
Mary Ainsworth's Baltimore Longitudinal Study: Methods and Discoveries
Mary Ainsworth's Caregiver Sensitivity Scales: Observation and Evidence
References
Ainsworth, M. D. S. (1967). Infancy in Uganda: Infant care and the growth of love. Johns Hopkins Press. Yale eHRAF bibliographic record.
Ainsworth, M. D. S., Blehar, M. C., Waters, E., and Wall, S. (1978). Patterns of attachment: A psychological study of the Strange Situation. Lawrence Erlbaum Associates. https://doi.org/10.4324/9781315802428.
Bretherton, I. (2013). Revisiting Mary Ainsworth’s conceptualization and assessments of maternal sensitivity-insensitivity. Attachment and Human Development, 15(5–6), 460–484. https://doi.org/10.1080/14616734.2013.835128.
Duschinsky, R. (2020). Mary Ainsworth and the Strange Situation Procedure. In Cornerstones of attachment research. Oxford University Press. https://doi.org/10.1093/med-psych/9780198842064.003.0002.
Madigan, S., Deneault, A.-A., Duschinsky, R., Bakermans-Kranenburg, M. J., Schuengel, C., van IJzendoorn, M. H., Ly, A., Fearon, R. M. P., Eirich, R., and Verhage, M. L. (2024). Maternal and paternal sensitivity: Key determinants of child attachment security examined through meta-analysis. Psychological Bulletin, 150(7), 839–872. https://doi.org/10.1037/bul0000433.
Madigan, S., Fearon, R. M. P., van IJzendoorn, M. H., Duschinsky, R., Schuengel, C., Bakermans-Kranenburg, M. J., Ly, A., Cooke, J. E., Deneault, A.-A., Oosterman, M., and Verhage, M. L. (2023). The first 20,000 Strange Situation procedures: A meta-analytic review. Psychological Bulletin, 149(1–2), 99–132. https://doi.org/10.1037/bul0000388.
Waters, E., Vaughn, B. E., Bretherton, I., van Rosmalen, L., and Marvin, R. S. (2026). The continuing relevance of Mary Ainsworth’s classic, Infancy in Uganda (1967/2026). Attachment and Human Development. Advance online publication. https://doi.org/10.1080/14616734.2026.2740913.