evaluation

• babies and carers behave more naturally in their own homes 


  study was carried out in the families' own homes without the presence of observers. this means that the babies behaviour wouldn't have been largely affected by the study taking place. therefore we can say that the study has good external validity.
• longitudinal design


  the same children were followed up regularly - this type of study has more validity than a cross-sectional study because it is not affected by the confounding variable of individual differences.
• limited sample

  the sample size of 60 was good considering how much information was collected from each family however all families were from the same district and social class so we cant generalise the findings to other cultures due to a difference in child-rearing practices across the globe. this study was also done more than 50 years ago.
• problem studying the asocial stage

  the asocial stage is suggested to be in the first few weeks of a infant's life at a point where they are pretty immobile. this means that it is quite difficult to observe characteristics that tend to this stage in forming attachments because there isn't much behaviour to observe.
• collectivist cultures and multiple attachments

  in collectivist cultures it is more likely that infants will form multiple attachments as soon as possible due to the family nature of working together jointly in everything. this suggests that Schaffer and Emerson's theory is only relative to the culture in Glasgow and is not generalisable