Twins and doubles have been making unsettling appearances in Gothic novels and horror films for decades. They have an even longer history that goes back to, at least, The Comedy of Errors. There’s something about twins that gives them great horrific potential. Their extreme similarity, the fact they are virtually indistinguishable and purportedly have deep connections are the kinds of elements that get repeatedly exploited for dramatic purposes.

It is not a coincidence that evil twins in horror and the Gothic tend to be identical (with the odd exception, like 1970’s Goodbye Gemini). The scariest thing about evil twins is, after all, that they embody repetition, and “repetition of the same thing” is one of the elements psychoanalyst Sigmund Freud identified as being connected to the effects of the “uncanny” in his influential 1919 essay of the same name.

The “unheimlich”, or uncanny, involves the experience of something familiar being rendered unfamiliar or of something new being experienced as strangely familiar. This is the case with identical twins, who tend to populate film more than literary fiction, given the reliance on images in film.

The most memorable example of the visual use of identical twins in horror is that of the Grady sisters in The Shining (1980). Although the sisters were not identical twins in Stephen King’s source novel, Lisa and Louise Burns’s audition made director Stanley Kubrick change his mind – identical twins were just spookier.

Accidental though this choice may have been, it plays with the idea of twins being reflections of one another – and at least one film critic has postulated that the careful alignment of the Grady sisters is an indication they may actually be the same person. Twins’ inherent uncanniness is often supplemented with additional supernatural powers. The Grady sisters are ghosts, but in other texts twins can also be telepathic.

More often, identical twins present subjective dichotomies for readers or viewers. They become allegorical representations of either moral or religious struggles. They externalise the division between the socialised and the repressed selves or else the battle between good and evil. In this sense, evil twins are extensions of the trope of the double (doppelgänger) or shadow self. This motif is particularly popular in Gothic texts, appearing in literary classics such as Edgar Allan Poe’s short story from 1839, William Wilson, and Robert Louis Stevenson’s Strange Case of Dr Jekyll and Mr Hyde (1886). But it also appears in cinema in examples like The Student of Prague (1913).

In films like The Black Room (1935) or Twins of Evil (1971) identical twins fall into the category of the double. They not only murder, but impersonate their good siblings, using their physical similarity for nefarious purposes. Admittedly, the use of evil twins in these films is driven by their respective narratives, but it is nevertheless possible to read them as examples of temptation where the evil self attempts to triumph over the good self – especially since the evil twin is ultimately defeated. Although some films, like Twins of Evil, cast real twin actors, it is quite common, as in The Black Room, for the same actor to play both twins – a decision that underscores the idea of the evil twin operating as the double.

Some films, such as The Other (1972), based on the Thomas Tryon novel, and Brian De Palma’s Sisters (1973), can subvert genre expectations by playing with viewers’ assumptions about twins and their traditional Gothic and horror roles. Both films initially portray their identical twins as polar opposites: one twin being angelic and obedient and the other one being evil and sociopathic. In both examples the evil twin either ends up haunting or overtaking the good twin. The narrative role of the evil twin as double is made evident as both collapse into one haunted individual.

Sisters is also interesting because it draws on the last of the qualities that define evil twins: their deep connection to each other. Danielle and Dominique (both played by Margot Kidder) are conjoined twins separated by a doctor who falls in love with Danielle. His reckless operation kills Dominique and is the cause of Danielle’s subsequent schizophrenia. In Sisters the connection between the siblings is physical in nature due to them being conjoined. But other horror texts, like Algernon Blackwood’s The Lost Valley (1910), explore the interdependence of twins in similar psychic ways. The outcome is rarely positive.

In David Cronenberg’s Dead Ringers (1988) – loosely based on the lives of doctors Stewart and Cyril Marcus – twin interdependence comes dangerously close to co-dependence. The brothers Elliot and Beverly Mantle (both played by Jeremy Irons) share everything, including their lovers. Yet, it is precisely the love of a woman that comes between them and sends them on a destructive spiral. At one point, Elliot develops a drug addiction to match Beverly’s, as he believes their troubles are due to a lack of synchronicity. Dead Ringers histrionically points towards the horrors of intense brotherly love and when it comes to exploring the nature of “evil” twins, nothing can match its intensity.

This piece was originally published on The Conversation.

Xavier Aldana Reyes is a Senior Lecturer in English Literature and Film at Manchester Metropolitan Museum.