The study is published by Gothenburg University, and takes as its starting point the work of Hanns Scharff, who worked for the German Luftwaffe in the Second World War, interrogating Allied airmen. He staged friendly conversations with his subjects, and got them to reveal more information than they realised.
The author of the Gothenburg University study is Simon Oleszkiewicz, who tells Radio Sweden Scharff's methods were surprisingly humane, considering the brutal interrogation methods used by other German personnel.
The study saw 380 participants simulate interrogations, half using the Scharff approach and the other simply asking direct questions, as laid down by the US army manual.
Two of the three studies have been financed by the American High-Value Detainee Interrogation Group. Researcher Simon Oleszkiewicz tells Radio Sweden that this study is part of an internal debate in the USA over which interrogation techniques work well.
He says that ethical methods are the most effective, and torture has been shown to not work. "It's obvious that Trump and all these other politicians who promote torture are not updated with either science of politics on that issue," Oleszkiewicz says.
He says the case of a fanatical terrorist who will not say anything is rarer than the media leads us to believe. "It's way more common that sources talk. To some extent."
Oleszkiewicz says often there are many sources, including people who are eager to share information, and the Scharff technique can be used to maximise gains.