Compared to prev research in2 institutionalisation, Rutter’s research has higher control over extraneous variables. previous orphans’ studies the children had often experienced trauma, neglect, abuse b4 being institutionalised + difficult to tell if any long-term effects were due to neglect+ abuse or the institutional care. However, in Rutter’s research, majority of Romanian orphans - handed over by loving parents who couldn't afford to keep them, = it was possible to study the effects of institutionalisation without these confounding variables. Therefore, increasing the internal validity