-value of longitudinal studies, by following development of adopted children you can determine whether the major effects of early institutional care disappear with sufficient time and care
-research applied in real life, research highlights the importance of early adoption before the sensitive period for attachment formation, now babies adopted within first week of birth
-individual differences, Rutter suggested some children may have received special attention meaning they had some attachment experiences therefore can't conclude institutionalisation leads to inability to form attachments
-deprivation is only one factor, romanian orphans also experienced poor physical conditions and the lack of cognitive stimulation impacted on their health and development therefore effects of institutional care go beyond emotional deprivation