From the Army Field Manual's chapter [PDF] on interrogations, which will now regulate CIA treatment of terror suspects:

8-65. Mutt and Jeff. (Interrogation) The goal of this technique is to make the source identify with one of the interrogators and thereby establish rapport and cooperation. This technique involves a psychological ploy that takes advantage of the natural uncertainty and guilt that a source has as a result of being detained and questioned. Use of this technique requires two experienced HUMINT collectors who are convincing actors. The two HUMINT collectors will display opposing personalities and attitudes toward the source. For example, the first HUMINT collector is very formal and displays an unsympathetic attitude toward the source. He may, for instance, be very strict and order the source to follow all military courtesies during questioning. Although he conveys an unfeeling attitude, the HUMINT collector is careful not to threaten or coerce the source. Conveying a threat of violence is a violation of the UCMJ.
8-66. At the point when the interrogator senses the source is vulnerable, the second HUMINT collector appears (having received his cue by a signal, hidden from the source, or by listening and observing out of view of the source), and scolds the first HUMINT collector for his uncaring behavior and orders him from the room. The second HUMINT collector then apologizes to soothe the source, perhaps offering him a beverage and a cigarette. He explains that the actions of the first HUMINT collector were largely the result of an inferior intellect and lack of sensitivity. The inference is that the second HUMINT collector and the source share a high degree of intelligence and sensitivity.
8-67. The source is normally inclined to have a feeling of gratitude towards the second HUMINT collector, who continues to show sympathy in an effort to increase rapport and control for the questioning that will follow. If the source’s cooperation begins to fade, the second HUMINT collector can hint that he is a busy person of high rank, and therefore cannot afford to waste time on an uncooperative source. He can broadly imply that the first HUMINT collector might return to continue the questioning. The Mutt and Jeff approach may be effective when orchestrated with Pride and Ego Up and Down, Fear Up and Down, Futility, or Emotional Love or Hate.

Good cop, bad cop, basically. A pretty far cry from vicious dogs and waterboarding.

--Michael Crowley