A study involving 132 8- and 9-year-old children, some of whom had been adopted into U.S. homes after spending at least a year and three-quarters in institutions in Asia, Latin America, Russia and Eastern Europe, and Africa, while others were adopted by the time they were 8 months old into U.S. homes from foster care in Asia and Latin America, having spent no or very little time in institutional care, has found that those adopted early from foster care didn't differ from children who were raised in their birth families in the United States. However, those adopted from institutional care performed worse on tests measuring visual memory and attention, learning visual information, and impulse control -- but not on tests involving sequencing and planning. The findings suggest that specific aspects of cognitive function may be especially vulnerable to postnatal experience.
(2010). Neurodevelopmental Effects of Early Deprivation in Postinstitutionalized Children.
Child Development. 81(1), 224 - 236.