User blog comment:Willbachbakal/Singleplayer Plasmids/@comment-175.139.62.248-20130909035314/@comment-1330314-20130910061334

The loss of their mental conditioning is actually what turns Little Sisters into Big Sisters -- effectively, they become murderously insane. I had an idea in mind for a Plasmid that'd let you adopt Little Sisters, but purely for gameplay reasons, and wouldn't actually be equippable (basically, it'd be the same as Tenenbaum's rescue Plasmid in BioShock, and would come alongside it).