Apophenia, the tendency to (incorrectly) infer patterns or connections in unrelated input, can be considered a commonplace effect of brain function. Taken to an extreme, however, it can be a symptom of psychiatric dysfunction, for example, as a symptom in paranoid schizophrenia, where a patient sees hostile patterns (for example, a conspiracy to persecute them) in ordinary actions.
Apophenia is also typical of conspiracy theory, where coincidences may be woven together into an apparent plot.