In my opinion, Ainsworth’s Strange Situation study into the subject of attachment is one of the most flawed studies I have ever come across. It was an experiment carried out in the 1970’s.
Ainsworth wanted to investigate how attachment in children aged 1 – 2 years vary and how the behaviours of that attachment manifest. To do this, the ‘Strange Situation’ procedure was created. An infant and their mother are left alone in a room. A stranger then enters before the mother leaves the infant alone with the stranger. The mother then returns before the stranger leaves. The mother then leaves the infant alone in the room for the first time. The stranger returns one last time, and then the mother. The stranger then leaves and once again the mother and infant are alone in the room. Each change of situation lasts 3 minutes before it is altered again, and the infants reaction if each change of environment is carefully observed and, according to Ainsworth, the findings of which can identify the infants attachment style.
The infants behaviour was measured under four specific categories. Separation anxiety (the unease of the child when left by the mother), the infants willingness to explore, stranger anxiety (the infants response to the stranger) and reunion behaviour (the way the mother was greeted on return). By observing these four behaviours, Ainsworth was sure she could identify the child’s attachment style.
The conclusion of the study was that there are three forms of attachment (secure attachment, resistant attachment and avoidant attachment), and that the type of attachment was determined by the behaviour of the mother (primary care giver).
However as I have already stated, I have many issues with this study. It does have a high reliability. This means that it achieves consistent results. For example, a study conducted in Germany found 78% of the children were classified in the same way at ages 1 and 6 years (Wartner, et al. 1994). However whether it has a high validity is a very different matter. The study only evaluates the infants attachment to the mother. The mother may not be the primary care giver. The infant may display completely different characteristics if put in the strange situation with a father or sibling. The infants behaviour may also change if put in the same situation at a different time of day or in a different state of mind. For example, a securely attached child may behave in a way considered to be insecurely attached if they were sleepy or coming down with a fever. The study has been criticised for breaking ethical grounds to as the child is out under stress and those, especially those labelled ‘insecurely attached’ would suffer anxiety as a result of the study. The participants in the study were all American. This means is is a sample bias and the results can not logically be applied to families outside America. And last and by no means least, the study has low ecological validity. The child was put in a situation they would never experience in day to day life. They would never be left alone with someone they had never seen before, and the stranger and parent were following a set script which may alter how they perceive their parent. If the mother is talking very differently than usual, this would cause confusion in the infant and may lead to a change in behaviour.
For the above reasons I do not think Ainsworth’s strange situation study is a valid way of studying attachment in children.
libbyayres 
I also agree that this study is very flawed questioning its validity. Due to the experiment being sample biased, only Americans, it is not applicable to be used in a more general context as for example different cultural upbringing may generally influence the behaviour of the infants. This would be interesting to see as this could show varying cultural tendencies and could be investigated further. Also too many external factors influence this experiment such as the mood of the infant that day, as libby said e.g. sleepiness, which could be completely different on the next day. Overall this study does not offer enough validity in order to investigate how attachment in infants manifests as well as how the behaviour varies.
Whilst at the time that it was published this study was seen as extremely useful within developmental psychology (as a lot of other studies have used the attachment styles presented in Strange Situation in their own research), I do agree with you that the methods within the study do possess a lot of issues. I agree with Libby and Lena that there could be numerous outside variables that could influence the way that a child displays attachment at that specific time. Also because of the population bias being towards Americans it is hard to generalise it to other cultures! For example, the Kibbutz tribe share child caring responsibilities and therefore there is less likely to be one single Primary Care Giver, therefore, if the strange situation was applied to the children from this tribe they would likely be classified as “insecure avoidant” because of a lack of preference to strangers as they would be used to a variety of people; yet this does not mean that their attachment is any less secure that a western child.
A study conducted by Van Izendorm and Kroonenberg reviewed 32 studies across 8 countries (all of which used the strange situation as the measure). This study found that the most common attachment was type B (secure) however type A (insecure avoidant) was more common in west Germany and type C (insecure resistant) was most common in China, Japan and Israel. However an issue with cross cultural studies is that some behaviours considered to not be beneficial for development may be seen as beneficial in other cultures.
Therefore i agree that although the majority of strange situation studies tend to find the majority of children and infants having secure attachment there is cross cultural variation that needs to be accounted for and what attachment behaviours are ‘normal’ in those cultures and not say because the infant does not have secure attachment they have the wrong attachment.
The study consists of many issues such as being unethical and in some areas does lack in validity however Mothers in the study were specifically chosen to be the primary caregiver. In most cases the primary caregiver tends to be the mother, this can only differ depending on lifestyle situations. So even if one or two of the mothers in the study were not the primary caregiver majority of them are more probable to be the primary caregiver of the child not damaging validity as much as you may suggest. However i do still agree that the study has issues with validity due to a child being a unreliable variable as every person has independent behaviours