Derailment (thought disorder)
In psychiatry, derailment (also loosening of association, asyndesis, asyndetic thinking, knight's move thinking, or entgleisen) is a thought disorder characterized by discourse consisting of a sequence of unrelated or only remotely related ideas. The frame of reference often changes from one sentence to the next.
In a mild manifestation, this thought disorder is characterized by slippage of ideas further and further from the point of a discussion. Derailment can often be manifestly caused by intense emotions such as euphoria or hysteria. Some of the synonyms given above (loosening of association, asyndetic thinking) are used by some authors to refer just to a loss of goal: discourse that sets off on a particular idea, wanders off and never returns to it. A related term is tangentiality—it refers to off-the-point, oblique or irrelevant answers given to questions. In some studies on creativity, knight's move thinking, while it describes a similarly loose association of ideas, is not considered a mental disorder or the hallmark of one; it is sometimes used as a synonym for lateral thinking.
- "The next day when I'd be going out you know, I took control, like uh, I put bleach on my hair in California."—given by Nancy C. Andreasen
- "I think someone's infiltrated my copies of the cases. We've got to case the joint. I don't believe in joints, but they do hold your body together."—given by Elyn Saks.
- "Look, having nuclear — my uncle was a great professor and scientist and engineer, Dr. John Trump at MIT; good genes, very good genes, OK, very smart, the Wharton School of Finance, very good, very smart — you know, if you’re a conservative Republican, if I were a liberal, if, like, OK, if I ran as a liberal Democrat, they would say I’m one of the smartest people anywhere in the world — it’s true! — but when you’re a conservative Republican they try — oh, do they do a number — that’s why I always start off: Went to Wharton, was a good student, went there, went there, did this, built a fortune — you know I have to give my like credentials all the time, because we’re a little disadvantaged — but you look at the nuclear deal, the thing that really bothers me — it would have been so easy, and it’s not as important as these lives are — nuclear is powerful; my uncle explained that to me many, many years ago, the power and that was 35 years ago; he would explain the power of what’s going to happen and he was right, who would have thought? — but when you look at what’s going on with the four prisoners — now it used to be three, now it’s four — but when it was three and even now, I would have said it’s all in the messenger; fellas, and it is fellas because, you know, they don’t, they haven’t figured that the women are smarter right now than the men, so, you know, it’s gonna take them about another 150 years — but the Persians are great negotiators, the Iranians are great negotiators, so, and they, they just killed, they just killed us.” — given by Donald Trump 
Entgleisen (derailment in German) was first used with this meaning by Carl Schneider in 1930. The term asyndesis was introduced by N. Cameron in 1938, while loosening of association was introduced by A. Bleuler in 1950. The phrase knight's move thinking was first used in the context of pathological thinking by the psychologist Peter McKellar in 1957, who hypothesized that schizophrenics fail to suppress divergent associations. Derailment was used with this meaning by Kurt Schneider in 1959.
- Non sequitur (logic) and Non sequitur (literary device)
- Red herring
- Relevance logic
- SCIgen, a program that generates nonsense research papers by grammatically combining snippets; many of the sentences generated are individually plausible
- Train of thought
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- Elyn Saks: "A tale of mental illness — from the inside." TEDGlobal 2012. Recorded in June 2012. "Archived copy". Archived from the original on 2014-03-26. Retrieved 2014-03-26.
- "FACT CHECK: Donald Trump's 'Nuclear' Speech". Snopes.com. Retrieved 2018-09-06.
- Tony Thompson, Peter Mathias, Jack Lyttle, Lyttle's mental health and disorder, Edition 3, Elsevier Health Sciences, 2000, ISBN 0-7020-2449-X, pp. 136, 168-170