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Not all attachments are alike. Some infants are confident and easily comforted; others appear anxious, or oddly detached, or caught between wanting comfort and resisting it. Turning these clinical impressions into a measurable, replicable classification was the achievement of Mary Ainsworth's Strange Situation, one of the most influential procedures in developmental psychology. This lesson examines how the Strange Situation works, the behaviours it measures, and the attachment types it identifies — secure, insecure-avoidant and insecure-resistant — together with Ainsworth's explanation of why these patterns arise. Understanding the procedure in detail matters because it supplies the attachment classifications on which so much later research, including the cross-cultural work in the next lesson, depends.
Key term: the Strange Situation is a controlled observational procedure devised by Mary Ainsworth to assess the quality of an infant's attachment to a caregiver. Typically used with infants aged 9–18 months, it takes place in an unfamiliar room and involves a structured series of separations and reunions.
This lesson addresses the types of attachment and the Strange Situation required by Edexcel 9PS0 — Paper 2, Topic 7: Child Psychology. You must know Ainsworth's Strange Situation — the procedure, the behavioural categories used to classify infants, and the three attachment types (secure, insecure-avoidant, insecure-resistant). This lesson follows directly from the theory lessons: the Strange Situation operationalises the secure-base idea and the separation/stranger anxiety introduced earlier, and its classifications are the infancy end of the continuity Bowlby proposed. In assessment-objective terms you should be able to describe the procedure, categories and types accurately (AO1), apply the classification framework to novel descriptions of infant behaviour (AO2), and evaluate the measure for reliability, validity, ethics and cultural bias (AO3).
Connects to…
Ainsworth and Bell (1970), with the procedure refined in Ainsworth et al. (1978), developed the Strange Situation as a standardised method for observing and classifying attachment behaviour in infancy.
| Episode | What happens | Behaviour it highlights |
|---|---|---|
| 1 | Parent and infant enter the room. | (Settling in) |
| 2 | Parent sits while the infant explores. | Exploration & secure base |
| 3 | A stranger enters, talks to the parent, then approaches the infant. | Stranger anxiety |
| 4 | Parent leaves; the stranger remains with the infant (first separation). | Separation anxiety; stranger anxiety |
| 5 | Parent returns and the stranger leaves (first reunion). | Reunion behaviour |
| 6 | Parent leaves the infant alone (second separation). | Separation anxiety |
| 7 | The stranger returns and tries to comfort the infant. | Stranger anxiety |
| 8 | Parent returns and the stranger leaves (second reunion). | Reunion behaviour |
Ainsworth and colleagues judged attachment type from five key behaviours:
Key term: secure-base behaviour is the infant's use of the attachment figure as a point of safety from which to explore — venturing out to play and returning to the caregiver when anxious or uncertain.
graph TD
SS[Strange Situation<br/>behaviours observed] --> PS[Proximity-seeking]
SS --> EX[Exploration / secure base]
SS --> SA[Stranger anxiety]
SS --> SEP[Separation anxiety]
SS --> RE[Reunion behaviour]
PS --> B[Type B: Secure ~66%]
EX --> B
SA --> B
SEP --> B
RE --> B
PS --> A[Type A: Insecure-Avoidant ~22%]
RE --> A
PS --> C[Type C: Insecure-Resistant ~12%]
RE --> C
style B fill:#27ae60,color:#fff
style A fill:#e67e22,color:#fff
style C fill:#e74c3c,color:#fff
Based on observations of around 100 middle-class American infants, Ainsworth identified three main attachment types.
| Behaviour | Description |
|---|---|
| Proximity-seeking & secure base | Stays reasonably close and uses the caregiver as a secure base for exploration |
| Exploration | Explores confidently and freely while the caregiver is present |
| Separation anxiety | Shows moderate distress when the caregiver leaves |
| Stranger anxiety | Shows some wariness of the stranger, especially when the caregiver is absent |
| Reunion behaviour | Greets the caregiver positively on return; seeks comfort and is quickly soothed |
Secure attachment is associated with a caregiver who is sensitive and responsive to the infant's needs and signals — the caregiver-sensitivity hypothesis.
| Behaviour | Description |
|---|---|
| Proximity-seeking & secure base | Does not seek proximity; does not use the caregiver as a secure base |
| Exploration | Explores freely but independently of the caregiver |
| Separation anxiety | Shows little or no distress when the caregiver leaves |
| Stranger anxiety | Shows little stranger anxiety; may be as content with the stranger as with the caregiver |
| Reunion behaviour | Avoids or ignores the caregiver on return; shows little interest in being comforted |
Insecure-avoidant attachment is associated with a caregiver who is rejecting or consistently unresponsive. The infant has learned that bids for comfort are not met, and so minimises them.
| Behaviour | Description |
|---|---|
| Proximity-seeking & secure base | Stays very close, reluctant to leave the caregiver; poor use of the secure base |
| Exploration | Explores less than secure or avoidant infants |
| Separation anxiety | Shows intense distress when the caregiver leaves |
| Stranger anxiety | Shows strong stranger anxiety; not easily comforted by the stranger |
| Reunion behaviour | Seeks comfort but simultaneously resists it (reaches to be picked up, then pushes away); ambivalent and hard to settle |
Insecure-resistant attachment is associated with a caregiver who is inconsistently responsive — sometimes attentive, sometimes neglectful — so the infant cannot predict whether bids for comfort will be met, and therefore both demands and resists contact.
Ainsworth's central explanatory claim — the caregiver-sensitivity hypothesis — is that attachment type is determined chiefly by the caregiver's sensitivity to the infant's signals. From her earlier naturalistic observations of mothers and infants in Uganda and Baltimore, Ainsworth concluded that mothers of secure infants were more sensitive, accepting, cooperative and emotionally accessible, whereas mothers of insecure infants tended to be less responsive, more rejecting (associated with avoidance) or inconsistent (associated with resistance). This explains why the three patterns arise: the infant builds an expectation of how reliably comfort is available and adjusts its behaviour accordingly — confidently using a base it trusts (secure), suppressing bids it expects to be rebuffed (avoidant), or anxiously over-monitoring a caregiver whose responses are unpredictable (resistant). This ties the Strange Situation directly back to reciprocity, synchrony and sensitive responsiveness from the first lesson, and it is the engine behind the predictive validity discussed below.
It also helps to understand why the procedure is structured as it is. The eight episodes deliberately escalate mild stress — first the unfamiliar room, then a stranger, then separation, then being left entirely alone — because attachment behaviour is displayed most clearly when the attachment system is activated. A contented, unstressed infant may explore happily whatever its attachment type; it is when the infant is anxious that the differences in how it uses (or fails to use) the caregiver become visible. This is exactly why reunion behaviour — when the stressed infant must "decide" how to respond to the returning caregiver — is the single most informative category.
The escalation also builds in two separations and two reunions, not one, which increases the reliability of the observation: a single reunion could be idiosyncratic (the infant might simply have been mid-tantrum), but a consistent pattern across both reunions gives observers firmer grounds for a classification. Similarly, the design cleanly separates the effect of the stranger from the effect of separation: episode 3 introduces the stranger while the parent is still present, whereas episode 6 removes the parent altogether, so an observer can tell whether an infant's distress is driven by the unfamiliar adult, by the loss of the caregiver, or by both. This careful structuring is part of what gives the Strange Situation its standardisation and its comparability across infants — a strength you can turn into an evaluative point about internal validity.
Main and Solomon (1986) later identified a fourth type — Type D: disorganised attachment — after reviewing some 200 filmed Strange Situations that observers had struggled to force into Ainsworth's three categories. These infants lack a consistent strategy for dealing with separation and reunion. Their behaviour may include approaching the caregiver while looking away, freezing or dazed "trance-like" expressions, contradictory behaviours (clinging while leaning away, or approaching then abruptly retreating), stereotyped movements such as rocking, and overt signs of apprehension towards the caregiver. Where an infant with a Type A, B or C attachment has some organised strategy for managing the stress of reunion — even the avoidant infant's strategy of down-playing its needs is a coherent adaptation — the disorganised infant appears to have no coherent strategy at all, which is the defining feature of the type.
In practice Type D is treated as a secondary classification layered on top of the original three: a coder first assigns a "best-fitting" A/B/C category and then notes whether disorganised behaviours are also present, so an infant may be classified, for example, as "disorganised/secure" or "disorganised/resistant". Reviews suggest disorganised attachment is far from rare — roughly 15% of infants in low-risk community samples, rising steeply (to well over half in some studies) in samples where maltreatment or serious parental difficulty is present. Its most influential explanation, developed by Main and Hesse (1990), is that disorganisation arises when the caregiver is frightening or frightened — for instance because of unresolved loss or trauma of their own. This creates an unresolvable paradox for the infant: the person who is biologically its haven of safety is simultaneously the source of alarm, so the attachment system is activated and the fear system triggered by the same figure, and the infant's behaviour collapses into contradiction. Note that the Edexcel content centres on Ainsworth's three types (A, B, C); Type D is an important later addition worth knowing for evaluation. Its existence is also a useful evaluative point in itself: because Ainsworth's original three-way scheme could not accommodate these infants, the need for a fourth category shows that the classification, however reliable, was not initially exhaustive — a reminder that even a well-validated measure can miss real patterns until researchers look again. It also carries a clinical significance the original three types do not, since disorganised attachment in infancy is among the stronger early predictors of later behavioural and mental-health difficulties.
Because AO2 questions often present a short vignette and ask you to identify the likely attachment type, it is worth rehearsing the reasoning. Consider three infants in the Strange Situation:
The diagnostic move in every case is to weight reunion behaviour most heavily, and to read the other categories in its light. A common exam error is to classify from separation distress alone — but a resistant and a secure infant may both be distressed by separation; what distinguishes them is whether the returning caregiver can settle the infant (secure) or not (resistant).
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