"Good cop, bad cop", also called the Mutt and Jeff technique, is a psychological tactic used in interrogation and negotiation, in which a team of two people take opposing approaches to the subject. One interrogator adopts a hostile or accusatory demeanor, emphasizing threats of punishment, while the other adopts a more sympathetic demeanor, emphasizing reward, in order to convince the subject to cooperate.
Origin:
The technique originated as an interrogation tactic in early 20th-century American policing. It evolved from older, harsher "third-degree" physical methods into a psychological approach (popularized post-WWII) .
Examples in life:
- A manager allows a supervisor to be the "bad cop" to handle poor performance, allowing the manager to maintain a friendly, supportive image.
- One parent acts strict about chores, while the other is lenient, forcing the child to listen to the strict one to gain favors from the lenient one.
- From Wiki + with editing
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We all have seen "good cop, bad cop" scenes in movies (eg. L.A. Confidential). And might have experienced such in work places, either done to co-workers or to ourselves, by the management. To be honest, I hated it when I saw it in the office.
But growing up, I never felt it from my parents. Maybe I was obedient enough or maybe they were just too busy with my brother. 
Actually this APAD was triggered by a post from 笑壇 two days ago, where I commented: "一個唱紅臉一個唱白臉" about their parenting. 
Wish All a Happy Easter Sunday!
