The SST has been criticised for assuming that attachment types remain the same for the duration of the infants life. It does not take into account changes in family (such as parent divorce or death of one parent etc) which may change the attachment type as Melhuish suggests. However, Wartners further research found that 78 per cent (a large majority) of childrens attachment types will remain the same. The SST has been praised for being reliable. Smith and Noble tested the SST in a realistic environment and their results replicated those found in the lab showing ecological vadility.
Ijzendoorn did 32 SST studies throughout the world and the results were similar thoughout 70 per cent secure and 30 per cent insecure. The SST has been repeated many times with similar results suggesting the results are reliable. Perhaps the biggest critism of the SST is the lack of consideration toward cross-cultural and cross-class differences. Takahashis study (taken in Japan) suggests that a higher proportion of insecurely attached infants are resistance rather than avoidant.
However, the results found in Japan can be seen to be influenced by the difference in child rearing practises in the Japanese culture. Japanese children became overly distressed when left by their mother. Japanese mothers rarely leave their children so the situation was too strange for the infant, hence the distress show. Similarly, Grosseman, brought the SST to Germany and found as oppose to Japanese infants, there were more avoidant attatchments in German children.
Again, this can be explained by the different child-rearing culture, German children are far more used to being left alone and therefore will show less anxiety where as the SST would say this lack of anxiety was due to an insecure attachment. The SST has not only been criticised for not taking into account major influences such as culture and class but also for ignoring past experiences children will have had with care givers, for example children who had experienced regular day-care are likely to react differently to those who had not.