|"There is no war within the walls. Here we are safe. Here we are free."|
|— A Dai Li agent brainwashing Jet.|
Brainwashing is the alteration or control of someone's mind through various methods. Such techniques were first developed by Long Feng in order to incapacitate those who opposed him and utilized by the Dai Li during the Conspiracy of Ba Sing Se to maintain cultural order and keep citizens from speaking of the Hundred Year War. The technique allowed the Dai Li to change attitudes, alter beliefs, augment personalities, and erase an individual's memories. During the rise of the Earth Empire in 171 AG, Doctor Sheng combined the enhanced indoctrination techniques of the Dai Li with modern technology to create a more permanent way to control people's mind by using magnetic waves to alter their brain.
The method was used on Jet when he was arrested, following his claim that Iroh and Zuko were firebenders. After chiding a downcast Joo Dee for falling behind in her duties, Long Feng induced a hypnotic state over her by reciting a special phrase, indicating that she had been brainwashed in the past. When Team Avatar infiltrated the Dai Li base underneath Lake Laogai, they saw a roomful of women being brainwashed into believing they were Joo Dee, ready to carry out the Dai Li's bidding.
Later, during a battle in the underground base, Long Feng managed to hypnotize Jet with the same phrase, "the Earth King has invited you to Lake Laogai", prompting him to respond with, "I am honored to accept his invitation", before proceeding to attack Avatar Aang.
During the rise of Kuvira's Earth Empire, Doctor Sheng began to research more effective methods for reeducating the prisoners Kuvira sent to her reeducation camps, which culminated in the creation of a machine that used magnetic waves to alter a person's brain in a more permanent manner. She and Commander Guan used this technology to influence the gubernatorial elections in the State of Gaoling by forcing the majority of its citizens to support Guan. They also used this technique to turn Mako, Bolin, and Asami into loyal soldiers to be used against Korra, and brainwashed King Wu into using his authority to speed up the election process, ensuring a landslide victory for Guan.
Doctor Sheng and Guan attempted but failed to also brainwash Kuvira, who managed to escape to Zaofu, where she and Baatar Jr. combined forces to create a machine capable of negating the effects of Sheng's magnetic waves. After a final showdown with the remnants of the Earth Empire, this machine was used to counter the brainwashing effects of everyone subjected to Sheng's machine, effectively releasing them from Guan's control.
The Dai Li often brought victims to their secret headquarters beneath the surface of Lake Laogai where they would proceed to brainwash them. During the process of brainwashing, agents would repeatedly recite anything they wished for the victims to believe.
When the Dai Li were brainwashing Jet, they used a dimly lit lantern that slowly traveled on a circular rail around the agent brainwashing him while stone cuffs prevented him from moving his arms, legs, or head. The agent repeated phrases to assure Jet he was safe, and that there was no war within the walls.
In the case of brainwashing the young women, the women would simultaneously repeat the words of a single agent. The process could also give the subject a secondary task, to be accomplished after saying the trigger-phrase "The Earth King has invited you to Lake Laogai." Long Feng used this code phrase on both Jet and Joo Dee.
With the advancement of technology, Doctor Sheng was able to greatly improve the reliability and permanence of brainwashing, as people subjected to the method of the Dai Li would more often than not return to their normal selves over time. She did so by combining the ancient techniques with modern technology to create a machine capable of altering a person's brainwaves by subjecting them to magnetic waves: the victim would be strapped to a chair, and a metal cap with wires connected to the machine was placed on their head. While subjecting the victim to electromagnetic shocks, the instructor would give them their orders, which could be malicious in nature and instruct them to hurt someone, or benevolent to reverse the effect of the initial brainwashing.
One Dai Li agent was specifically assigned as an "instructor" by Long Feng. In truth, he was hired to brainwash a number of women into becoming Joo Dees and to recreate them as the Grand Secretariat's reliable propaganda machine. He was responsible for teaching the Joo Dees "charm, poise, and the dissemination of the Dai Li party line." This particular Dai Li agent was assigned this task entirely on account of his smile, which became the "perma-grin" worn by every Joo Dee.
When brainwashed, people's minds are rewritten into believing anything the brainwasher states or forgetting information the brainwasher wishes to erase from their mind. They will also obey any commands given to them by their handler.
Long Feng was able to activate a subject's secondary task with the code phrase. When this was done, the subject entered a trance state and answered the code with "I am honored to accept his invitation." In Jet's case, the task was to attack Aang. In Joo Dee's case, she was told to wait for specific orders.
Sheng's machine altered its victims brainwaves to the point where they were placed under complete control of the instructor. The electromagnetic pulses used to recalibrate a person's mind do have the side effect that the victim suffers from complete amnesia for the time they have been subjected to the brainwashing technique.
There are only three known methods of curing brainwashing.
The waterbending technique of healing has been known to be capable of bringing a subject out of their hypnotic state. Jet's brainwashed state was broken when Katara used her healing abilities on him.
Oftentimes, familiar surroundings are able to slowly regenerate the memory of a brainwashed victim or even completely reverse the effects of brainwashing. Visiting the Dai Li's secret underground base evidently revived Jet's memory of being captured and brought there by Dai Li agents. After a brief duel ensued with Long Feng battling Aang and Jet, Long Feng was able to bring Jet under his control by reciting the code phrase, which prompted Jet to attack Aang. However, when Aang reminded Jet that he was a Freedom Fighter, his brainwashed state was once again broken.
Modern brainwashing is based on magnetic waves set on a specific frequency to alter the brainwaves of its victim. By reverse engineering the process and figuring out the specific settings used to alter the brainwaves, the brainwashing effect can be lifted by subjecting them to the machine again.
- A large group of women who called themselves "Joo Dee"
- People who caused problems relating to the Hundred Year War in Ba Sing Se during Long Feng's reign as Grand Secretariat
- Asami Sato
- Royal Earthbender Guards
- Voters during the election for governor in Gaoling
- Doctor Sheng's method to control people is similar to the technology used in transcranial magnetic stimulation therapy in the field of neuropsychiatry, which similarly uses electromagnetic waves to manipulate the neural pathways of a human brain.