MUST READ NeuroLogica Blog » Reality Testing and Metacognitive Failure

Feb 20 2014. Steve Novella at his brilliant clear speaking best, about the core of many real problems in this fallible world we live in.  
(As Steve's terms of website  usage rules prohibit copying, so Pundit will sparingly use some reported speech to indicate the topic:)

Novella asks the reader to imagine coming home to your spouse and finding someone who looks and acts exactly like your spouse, but you have the strong feeling that they are an imposter. He then supposes that this person doesn’t “feel” like your spouse. Steve goes on to say "something is clearly wrong", and that in this situation most people conclude that their spouse is, in fact, an imposter. In some cases this has even lead to the murder of the “imposter” spouse, he says.

He mentions then the neurological syndrome known as Capgras delusion – a sense of hypofamiliarity, that someone well known to you is unfamiliar. And also mentions the opposite of this – hyperfamiliarity, the sense that a stranger is familiar to you, known as Fregoli delusion. Suffers often feel that they are being stalked by someone known to them but in disguise, he says.

Highly recommended
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Novella goes on to say that a recent article by psychologist Philip Garrans explores these issues in detail, but with appropriate caution. We are dealing with complex concepts and some fuzzy definitions. But in there are some clear mental phenomena that reveal, at least to an extent, how our minds work...

Read the whole thing @ NeuroLogica Blog » Reality Testing and Metacognitive Failure:

Refers to
Pathologies of hyperfamiliarity in dreams, delusions and déjà vu

Philip Gerrans
Department of Philosophy, University of Adelaide, Adelaide, SA, Australia

The ability to challenge and revise thoughts prompted by anomalous experiences depends on activity in right dorsolateral prefrontal circuitry. When activity in those circuits is absent or compromised subjects are less likely to make this kind of correction. This appears to be the cause of some delusions of misidentification consequent on experiences of hyperfamiliarity for faces. Comparing the way the mind responds to the experience of hyperfamiliarity in different conditions such as delusions, dreams, pathological and non-pathological déjà vu, provides a way to understand claims that delusions and dreams are both states characterized by deficient “reality testing.”
Front. Psychol., 20 February 2014 | doi: 10.3389/fpsyg.2014.00097