Released by the Freedom of Information Act.
The threat to inflict pain, for example, can trigger fears more damaging than the immediate sensation of pain." Unde.
For example in "Threats and Fears," the CIA authors note that "the threat of coercion usually weakens or destroys resistance more effectively than coercion itself.
To get the information that is needed there is nothing withheld short of torture.
This Document is a thorough description of how the CIA recommends interrogating a subject.
Released by the Freedom of Information Act