Positive or negative expectations about circumstances, events, or people that may affect a persons behavior toward them in a manner that he or she (unknowingly) creates situations in which those expectations are fulfilled.
In other words, causing something to happen by believing it will come true
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Example 1: An employer sees a new employee and automatically expects him to be disloyal. The employer then treats the employee in a way to elicit the very response he concluded.
Example 2: Labeling someone a "criminal," and treating that person as such, may foster criminal behavior in the person who is subjected to the expectation, thus creating a self fulfilling prophecy
A twat who claims he's only behaving like a twat in defence of the fact that other people keep calling him a twat behind his back.
Similar to a self-fulfilling prophecy but more personal, and often used as a defense mechanism, usually by men to avoid ever having to engage with anyone emotionally, or say sorry.
Their phrase of choice should you ask them why they're behaving like a twat is of course: 'Are you calling me a twat then!?' and then centre all their twatness upon you as you obviously must be the source of why everyone thinks they're a twat, and are no longer inviting them to any more social events.
I can't be bothered to try and make sense of the man anymore, he just seems to be a self-fulfilling twat.