there were many orphan studies before the Romanian orphans became available to study. these often involved children who experienced loss or trauma before they were institutionalised. neglect, abuse and breheavement meant it was hard to observe the effects of institutionalisation in isolation. the children were affected by multiple factors functioning as confounding variables. this means we can be faidly sure that differences in institutionally cared for children are the result of this type of care (high internal validity)