A torture manual created by psychologists in the 1950s entitled The Manipulation of Human Behavior is freely available online. Included are these scary sounding chapters:

1 The Physiological State of the Interrogation Subject as it Affects Brain Function 19 Lawrence E. Hinkle, Jr. 2 The Effects of Reduced Environmental Stimulation on Human Behavior: A Review 51 Philip E. Kubzansky 3 The Use of Drugs in Interrogation 96 Louis A. Gottschalk 4 Physiological Responses as a Means of Evaluating Information 142 R. C. Davis 5 The Potential Uses of Hypnosis in Interrogation 169 Martin T. Orne 6 The Experimental Investigation of Interpersonal Influence 216 Robert R. Blake and Jane S. Mouton 7 Countermanipulation through Malingering 277 Malcolm L. Meltzer

From the text:

From the theoretical point of view it is hard to escape the conclusion that a man is best able to give accurate information when he is in an optimal state of health, rest, comfort, and alertness, and when he is under no threat. This would seem to be the optimal situation for interrogation. Any attempt to produce compliant behavior by procedures which produce tissue damage, disturbances of homeostasis, fatigue, sleep deprivation, isolation, discomfort, or disturbing emotional states carries with it the hazard of producing inaccuracy and unreliability.

However, it is often necessary for the interrogator to question people who are experiencing moderately severe effects of illness, injury, fatigue, discomfort, or anxiety. A body of practical experience indicates that relatively reliable information can be obtained from most such people, if the information sought is neither complex nor extensive. The interrogator faces two special hazards under these circumstances. First, the source may have a fairly serious degree of mental disturbance that is not immediately evident and it may escape the interrogator's attention. Second, any informant in a threatening situation is liable to say whatever will please his captors, even though he may not do so intentionally. These ever-present hazards of interrogation are enhanced under adverse circumstances. It may be assumed, in the absence of evidence to the contrary, that the simpler, the briefer, and the more readily verifiable the information that is sought, the more likely is the evidence of the source to be of value.