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. They don’t “feel” like your spouse. Something is clearly wrong. In this situation most people conclude that their spouse is, in fact, an imposter. In some cases this has even led to the murder of the “imposter” spouse.

This is a neurological syndrome known as Capgras delusion – a sense of hypofamiliarity, that someone well known to you is unfamiliar. There is also the opposite of this – hyperfamiliarity, the sense that a stranger is familiar to you, known as Fregoli delusion. Sufferers often feel that they are being stalked by someone known to them but in disguise.

Psychologists and neuroscientists are trying to establish the wiring or “neuroanatomical correlates” that underlie such phenomena. What are the circuits in our brains that result in these thought processes? 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.

The “reality testing” model discussed by Garran reflects the overall hierarchical organization of the brain. There are circuits that subconsciously create beliefs, impressions, or hypotheses. We also have “reality testing” circuits, specifically the right dorsolateral prefrontal circuitry, that examine these beliefs to see if they are internally consistent and also consistent with our existing model of reality. Delusions, such as Capgras and Fregoli, result from a “metacognitive failure” of these reality testing circuits.

Garran and others argue that dreams are a normal state we all experience in which our reality-testing circuitry is either off or hypofunctioning. This is why our dreaming selves accept dream events that are clearly internally inconsistent or at odds with our model of reality. When we wake up, if we remember our dream, we are often struck by how “bizarre” our dream was and marvel at how our dreaming self accepted the clearly unreal dream.

The question Garran explores is whether or not pathological delusional states are neuroloanatomically similar to the dreaming state. Both, he argues, may result from a failure of reality testing. Part of the problem of exploring this hypothesis is that “reality testing” is a broadly defined concept. What, exactly, is the process? It seems to be a higher level inference about what is likely to be real based upon logic, internal consistency, and existing knowledge. 

Here is my own synthesis of what we currently know about how our brains work with respect to belief and reality testing:

There are multiple identified processes, acting mostly subconsciously, that “present” tentative beliefs or conclusions to our conscious awareness. These processes include our sensory perceptions, which are highly constructed and are not objectively reliable. Our brains not only construct our perceptions but give them meaning. We don’t just see shapes, we see objects that have a reality and a purpose. We also see people, who have emotional content, including familiarity. Locations also are imbued with a sense of familiarity or unfamiliarity.

Our memories are also highly constructed and malleable. We update our memories with new information every time we recall them. They become part of our dynamic internal model of reality. 

There are also a host of biases and needs pushing our model of reality and our construction of events in a direction that is emotionally comforting and satisfying to us.

Further, we have a set of heuristics or inherent logic by which we, by default, attempt to make sense of the world. This includes an inherent (flawed) sense of probability. There are also inherent tendencies, such as the tendency to see patterns, to detect agency in others and in our environment, and to weave compelling narratives.

All of these things are combined together to give us an impression of reality, of what is going on. But our brains also have circuitry which will then filter out or test these impressions to see if they make sense. The net effect – what you ultimately believe about reality – is a complex interaction of all of these moving parts. If the end result is congruous with existing and desired beliefs, then we are content. If they are incongruous, then this results in what psychologists call “cognitive dissonance.” We then marshal our reality-testing circuitry to resolve the conflict, usually through motivated reasoning and rationalization, and once the cognitive dissonance is resolved we are rewarded with a shot of dopamine to our reward circuitry.

The end result is about the balance of all of these circuits. If your biases and emotional motivations are relatively minor, and your metacognitive reality testing is relatively robust, then you will tend to come to a reality-based rational conclusion. (This is still dependent on your factual knowledge, culture, etc. but at least the process will likely be rational.)

If, however, you have impaired reality testing, you are more likely to accept whatever notion your subconscious processing results in, even if it makes no sense. Psychologists refer to a pathological lack of reality testing as a delusional disorder – persistent beliefs that are at clear odds with external reality.

However, even in those with intact reality testing, the motivation to accept a belief that is at odds with reality may overcome such testing. We call this “motivated reasoning” – the twisting of our reality testing process to confirm desired beliefs, or reject unwanted beliefs, rather than objective reality testing.

There may also be a problem with the subconscious circuitry that is making the “first pass” construction of reality, and these flaws or errors may overwhelm our reality testing. That is what Capgras and Fregoli are – errors in the detection of familiarity that present a highly incongruous picture of reality to our right dorsolateral prefrontal circuitry, which then struggles to deal with the incongruity. Often the reality-testing circuitry notices something is wrong, and confabulates a solution – my spouse is an imposter, or I am being followed by someone in disguise.

Confabulation (making stuff up) is a key component of how our brains resolve incongruities or cognitive dissonance. When the incongruity is great, then the tolerance for confabulation goes up. When our reality testing is impaired, confabulation is also unhinged. Confabulation is especially prominent in memory disorders. If, for example, a person with a severe short-term memory deficit meets someone who acts, or perhaps specifically states, that they are known to the person, but for whom they have no memory, they may simply confabulate prior interaction and knowledge in order to resolve the incongruity between current events and their memory deficit.

Even healthy and neurotypical individuals, however, will easily confabulate in order to resolve apparent incongruities between their memories and new information, or the memories of others. Some individuals are also highly emotionally invested in a belief or a particular narrative, and this can overwhelm their reality testing. This may include a penchant for conspiracy thinking, or a deeply held ideological, cultural, or personal belief.

We frequently see confabulation in patients who have had damage to a part of their brain resulting in impaired reality construction, causing dramatic incongruity. For example, a patient with a right hemisphere stroke may lose the very concept of the left side of their body and reality. When confronted with their left arm they will often state that the arm belongs to the examiner, or even that there is another patient in the bed with them. This is clearly at odds with reality, but they are certain the arm is not theirs because the circuitry that would generate the sense of ownership and control are damaged.

Conclusion

We still have a great deal to learn about brain circuitry and its complex interactions, but I think we are getting close to a reasonable working model of how our brains think. Subconscious processes create a hypothesized construction of reality out of our sensory input, memories, biases, heuristics, narratives, and emotional needs. Reality testing circuitry examines these hypotheses to see if they are internally consistent, compatible with our current models of reality, and if they serve our emotional needs. Our brains then struggle to come up with a resolution – a conclusion about what is probably true (or what we want to be true) based upon all of these simultaneous processes.

Understanding this process is helpful because it does shift the balance toward metacognition. Subconscious emotional processes have less of a hold on our thinking when we understand them. You can make a mental effort to think harder – meaning engaging your reality testing circuitry more robustly, rather than going with the flow of your subconscious processing. You can also impose an objective reference to external facts, and a formal process of logic onto your reality testing – you can, in other words, get better at reality testing.

This seems like a worthwhile endeavor.