- AO1- Hodges and Tizard. 65 British children, 4 months- 4 years. Stay, restored or adopted.
- AO2- Skodak and Skeels, IQ in orphanage and home for the mentally retarded.
- AO2- Quinton, showed mothers who had been in care lacked warmth and their children often ended up in care themselves
- AO2- Rutter, Romanian orphans adopted before age 2 showed normal attachment after showed disinhibited attachment