While there is no doubt Jordan Peele's newest horror piece Us will shock and amaze us in ways we do not yet know – like Get Out did – there are a few themes in it that deserve a thorough look before the film hits the big screen March 22 – if for no other reason than the ubiquity of those themes in cinema and other forms of art and their inherent interesting qualities as background information.

Probably the most prevalent of those themes from what we know of Us so far, is the doppelgänger, (German for "double walker") or non-genetically related double of a person – that double usually being an evil entity. Us – from what we know so far – centers on a family (played by Lupita Nyong'o, Winston Duke, Shahadi Wright Joseph and Evan Alex) battling their doppelgängers.

This certainly adds interesting challenges for the actors in playing two (essentially) separate people in Peele's film, and will most likely have some symbolic meaning of us being our own worst enemies – which actually ties in to what the doppelgänger as a neurological and psychiatric phenomenon can tell us about the neurobiology behind emotion and how we construct a sense of self (more on this below).

Yet, what of the doppelgänger's larger impression in art, culture, science and even history? Indeed, there are many documented occurrences of famous figures like President Abraham Lincoln (who allegedly saw his double the night of his inauguration), Queen Elizabeth I (who saw hers shortly before she died), and Percy Bysshe Shelley (who's story is below) encountering their doppelgängers very much in the flesh – and usually right before they died. Surely, considering the expressly social content in Get Out, Peele will draw on this huge record too.  

Spiritualists and mystics have often labeled the doppelgänger “a demon”, echoing that idea that they are a portent of doom. Others (including the extensive use of the doppelgänger in Gothic literature) have detailed it as some type of ghost, phantom or specter. Still others have said the doppelgänger is us traveling through a number of different dimensions or wormholes in time. Broadly relates a story about a man who was walking down the street when he saw himself walk by in the opposite direction. Eight years later, the same man walked past himself going the same way in the opposite direction (his story oddly echoes Goethe's story below). There is even a whole subreddit dedicated to these types of occurrences.

Science has proffered a number of explanations for the doppelgänger phenomenon. The evolutionary one basically says that because you don't see much of the diversity between how humans look in other species, it really isn't surprising to think there's someone who looks exactly like you somewhere. For instance, can you really tell two squirrels apart? Thus goes this explanation that maybe we are to some degree, just seeing what we want to see there, and that diversity does not really exist – at least, not to the level we believe. Ergo, there could be someone out there who looks exactly like you. The possibility of the genetic lottery randomly combining the same options a number of times also adds credence to this idea.

Still, other studies have pegged the likelihood of an exact doppelgänger as about 1 in 1 trillion. And even if there was a higher likelihood, this explanation really doesn't say anything about the malevolence that is so often ascribed to the doppelgänger.

What neurology and psychology have to say makes more sense (and is infinitely interesting). Psychology and neuroscience may hold a partial (but better) answer to this in describing "the doppelgänger phenomenon," or delusions characterized by a belief in a doppelgänger or some variant of it. These include hallucinations of seeing a double (known as "syndrome of subjective doubles" in psychiatry) and so-called "out of body experiences".

The lobes of the brain.

The medial temporal lobe. Source: American Journal of Neuroradiology.

"Autoscopy" (also spelled "Heautoscopy") is another component of the neurological and psychiatric explanation of the doppelgänger. It is characterized by seeing one's double at a distance and is often a symptom of schizophrenia, brain damage or epilepsy – particularly temporal lobe epilepsy, which often produces profound hallucinations and has also been correlated with intense religious visions. Even anti-Parkinson treatment with levodopa can cause all the delusions described in this article. These occurrences can also be co-morbid with other psychotic disorders and even bi-polar disorder.

"Polyopic autoscopy" is seeing more than one double. One case was noted of a patient who saw five doubles and was later found to have a tumor in his temporal lobe.  While another related phenomenon called "negative autoscopy" is not seeing one's reflection when looking in a mirror.

This type of psychiatric pathology can get even more bizarre than the doppelgänger phenomenon and include something seemingly right out of Invasion of the Body Snatchers. That, in fact, is basically what "Capgras Delusion" is: the belief that a person close to you is the same physically but that a different intelligence and personality is controlling them or that the person has been replaced by an identical looking impostor.

One interesting thing about Capgras: it generally does not occur in the sufferer when they are taking to the person who is the subject of their delusion over the phone (or otherwise out of sight). All is (relatively) normal and placid. It is when visuals are a factor that the delusion takes hold because of the specific wiring affected in the brain of the sufferer. Their facial recognition system is what is at fault here in the brain. As the incredible behavioral neurologist, researcher and author Dr. Vilayanur S. Ramachandran (whose books, especially "Phantoms in the Brain", I highly recommend interested parties seek out) has noted: this delusion causes incredible upset and fear in the sufferer too, when they fundamentally cannot rely on their faculty of visual recognition. Capgras can also happen with inanimate objects.

Dr. Ramachandran explains Capgras Delusion.

"Intermetamorphosis" is a variant of Capgras where the sufferer perceives that object of their delusion has been transformed physically and psychologically into another person.  

"Fregoli's Delusion" is similar to Capgras but different. It is the delusional belief that different people are in fact the same person changing form or in disguise. 

The best proof of how this all relates to emotion and our sense of self (besides the involvement of the temporal lobe in these various delusions) is ultimately in two hypotheses which have been proffered to explain these "syndromes of misidentification". The first is that of "prosopagnosia", or "face blindness", where all other intellectual faculties are intact but the ability to recognize familiar faces (including one’s own) is absent. This is often a direct result of damage to the temporal lobe or a disease affecting it, like Alzheimer’s Disease.   

The second hypothesis is the opposite of the first: it is over-identification, where the brain imputes too much information in identifying a face and consequently major emotional regions like the temporal lobe are over active.

Certainly the medical literature on this is very interesting in its own right.  Yet, no matter what the medical, psychological, or biological basis of the doppelgänger (if any) is, there have been a number of recorded instances of cultural luminaries seeing their doubles, often before death or some other horrible occurrence. Others have put in the historical record stories they themselves have encountered of the doppelgänger, likely with varying degrees of truth, yet they are all entertaining in their own right and have shaped the popular mind and zeitgeist for many years.

American politician and social reformer Robert Dale Owen related the story of 32-year-old French teacher Emilie Sagée who was teaching at a girl's school in Latvia in 1845. One day as she wrote at the chalkboard, her exact double came in and stood next to her, copying her every movement (still somehow – the story goes – she didn't see it). Thirteen of Ms. Sagée's students allegedly witnessed this. The next year, Sagée's double allegedly appeared again – this time in front of the entire school while Sagée could be seen working in the school's garden. When the students approached it, the double vanished. 

French novelist Guy de Maupassant was inspired to write his short story "Lui?" ("He?") after an 1889 experience – he alleged – with his doppelgänger, who he says dictated the story. He would later claim several experiences with his doppelgänger over the years. The author would be institutionalized in 1892 following a suicide attempt. He died one year later. De Maupassant had syphilis, which – if it damaged his temporal lobe – could explain his experiences with his double.   

The great author of "Faust", Johann Wolfgang von Goethe, wrote of an experience with his doppelgänger in his autobiography "Dichtung und Wahrheit" ("Poetry and Truth"). He describes riding to the town of Drusenheim to visit Frederike Brion, a young woman he was romantically involved with. As Goethe describes being "emotional and lost in thought" he saw his double dressed in a gray suit, trimmed with gold. Eight years later, Goethe found himself riding that same road to see Brion, this time wearing the gray suit with gold trim when that initial memory resurfaced in his mind and gave the writer great comfort.

Poet and husband to "Frankenstein" author Mary Shelley, Percy Bysshe Shelley, told his wife he had seen his double on several occasions – not long after he told Mary about this, he died at sea in an accident. One time, his double spoke to him, saying, "how long do you mean to be content?" Jane Williams, a close friend to Mary, had seen Percy's double when it passed by her window one night

Film, in its comparatively short history, has done a lot with the concept of the double in various permutations. Alfred Hitchcock’s 1958 magnum opus Vertigo being probably the finest example, where the double becomes the way to hide misdeeds and murder. David Lynch's Mulholland Dr. (which takes more than a few cues from Vertigo, something I've written about here) also touches on the idea of a double in the juxtaposition of the film's dream world and real life. In fact, the double often recurs in Lynch's work, as it also is a factor in 1997's Lost Highway and 2006's Inland Empire; only it is a factor in different ways in those films than it was in Mulholland Dr. in 2001.

A few other films about a double or doppelgänger include Christopher Nolan's The Prestige (2006) about two rival magicians, Brian De Palma's Obsession (1976) and Femme Fatale (2002), Charlie Chaplin's The Great Dictator (1940), Roman Polanski';s The Tenant (1976), Akira Kurosawa's Kagemusha (1980), and Ingmar Bergman's iconic Persona (1966) which also was a huge influence on David Lynch. Check out trailers for each of these below as all these movies are well worth watching.

As was said at the beginning of this piece, there is no doubt Jordan Peele will use Us's doppelgänger theme in new and impossible to predict ways. Nothing in this piece is meant to foresee Peele's work, merely to provide some scientific, historical, and artistic context for the doppelgänger theme as it has occurred throughout history and science. The hope being that that context may give the viewer a new appreciation of Us when we all finally get to see it March 22 of this year.

VERTIGO (1958) trailer.

MULHOLLAND DR. (2001) trailer.

LOST HIGHWAY (1997) trailer.

INLAND EMPIRE (2006) trailer.

THE PRESTIGE (2006) trailer.

OBSESSION (1976) trailer.

FEMME FATALE (2002) trailer.

THE GREAT DICTATOR (1940) trailer.

THE TENANT (1976) trailer.

KAGEMUSHA (1980) trailer.

PERSONA (1966) trailer.