This is an excerpt from Valerie Tarico's web series "Christian Belief Through The Lens of Cognitive Science"
In revival meetings or retreats, semi-hypnotic processes draw a potential convert closer to the toggle point. These include including repetition of words, repetition of rhythms, evocative music, and Barnum statements (messages that seem personal but apply to almost everyone– like horoscopes). Because of the positive energy created by the group, potential converts become unwitting participants in the influence process, actively seeking to make the group’s ideas fit with their own life history and knowledge. Factors that can strengthen the effect include sleep deprivation or isolation from a person’s normal social environment. An example would be a late night campfire gathering with an inspirational story-teller and altar call at Child Evangelism’s “Camp Good News.”
These powerful social experiences culminate in conversion, a peak experience in which the new converts experience a flood of relief. Until that moment they have been consciously or unconsciously at odds with the group center of gravity. Now, they may feel that their darkest secrets are known and forgiven. They may experience the kind of joy or transcendence normally reserved for mystics. And they are likely to be bathed in love and approval from the surrounding group, which mirrors their experience of God.
Also, military basic training seems to employ some of these methods too:
To do this, however, we need a form of psychological training that is able to forge individuals who can do this. That is why boot camp has evolved to become such a potent tool in today's military machine.
The most important single thing to know about boot camp is that it is 100 percent designed to reprogram children and civilians into warriors. It places within them a sense that they are expected to do important things, far more important things than could be expected from other 18-year-olds. This is all happening during one of the most intensely stressful periods of your life, when you are kept isolated from contact from your family and friends and taught that everything you were before entering the Marines was weak and lacking any real value until you too are a Marine. Cults are made this way too. I'm just saying. But in all seriousness, the psychological transformation of boot camp is a very intense and intentional effort by the Marine Corps to make warriors able to fight and kill out of kids who have just barely left high school. From the point that you graduate boot camp, you will be different and have parts of the Marine Corps culture as part of your psyche.
[...]
Now we move on to something else very important and why I say that it is "psychological" retraining. You go through the next few days running from place to place, doing this, that, this, that and you won't even realize ... you haven't slept in three days. Yeah, you will go about three days without sleep upon arrival. The whole time you are completely exhausted while running on adrenaline and hearing over and over, that you are inferior. Inferior to real Marines, which you aren't yet. You aren't thinking about it, but it is sinking in. You are completely tired and these things build up. Without realizing it, you start to believe that that which is being told to you is true, that there is a weakness in you and that you are less than perfect. In your current state, you believe them and that you must change to be good enough.
(Caveat: I've been through bootcamp)
I'm not sure you could call this brainwashing, though. Not any more than you can call singing and dancing in synchrony brainwashing or doing extreme rituals. Like someone else said, taboo the word "brainwashing"; the word itself has a bunch of negative connotations. Brainwashing in the popular sense also assumes a sort of permanence, which is probably a strawman of what's actually going on.
Some old SIAI work of mine. Researching this was very difficult because the relevant religious studies area, while apparently completely repudiating most public beliefs about the subject (eg. the effectiveness of brainwashing, how damaging cults are, how large they are, whether that’s even a meaningful category which can be distinguished from mainstream religions rather than a hidden inference - a claim, I will note, which is much more plausible when you consider how abusive Scientology is to its members as compared to how abusive the Catholic Church has been etc), prefer to publish their research in book form, which makes it very hard to review any of it. Some of the key citation were papers - but the cult panic was so long ago that most of them are not online or have been digitized! I recently added some cites and realized I had not touched the draft in a year; so while this collection of notes is not really up to my preferred standards, I’m simply posting it for what it’s worth. (One lesson to take away from this is that controlling uploaded human brains will not be nearly as simple & easy as applying classic ‘brainwashing’ strategies - because those don’t actually work.)
Reading through the literature and especially the law review articles (courts flirted disconcertingly much with licensing kidnapping and abandoning free speech), I was reminded very heavily - and not in a good way - of the War on Terror.
Old American POW studies:
Started the myth of effective brain-washing. But in practice, cult attrition rates are very high! (As makes sense: if cults did not have high attrition rates, they would long ago have dominated the world due to exponential growth.) This attrition claim is made all over the literature, with some example citations being:
a back of the envelope estimate for Scientology by Steve Plakos in 2000:
Iannaccone 2003, “The Market for Martyrs” (quasi-review)
Singer in particular has been heavily criticized; “Cult/Brainwashing Cases and Freedom of Religion”, Richardson 1991:
“Overcoming The Bondage Of Victimization: A Critical Evaluation of Cult Mind Control Theories”, Bob and Gretchen Passantino Cornerstone Magazine 1994:
Gomes, Unmasking the Cults (Wikipedia quote):
“Psychological Manipulation and Society”, book review of Spying in Guruland: Inside Britain’s Cults, Shaw 1994
Anthony & Robbins 1992, “Law, Social Science and the ‘Brainwashing’ Exception to the First Amendment”:
“Brainwashed! Scholars of cults accuse each other of bad faith”, by Charlotte Allen, Lingua Franca Dec/Jan 1998: