Scarlett Johansson stars in Jonathan Glazer’s “Under the Skin.” Courtesy of A24.

What is it that makes us human? What separates us from the artificial beings designed to mimic our behavior, store our knowledge and latch onto our daily lives like a vital appendage? Are our own relationships governed by organic thought or programmed responses? Is it in our nature to truly look at one another or only see what we want to see? And if the latter is the case, does that render our lives little more than an idealized fantasy?

These are a sampling of the questions raised and provocatively explored by two of the most fascinating films in recent memory. The first is Spike Jonze’s “Her,” the film I considered to be the best of 2013. The other one is Jonathan Glazer’s “Under the Skin,” which is easily the best film I’ve seen so far this year. Both pictures cast Scarlett Johansson as a non-human entity whose designated function is to seduce men with her contrived yet credible female wiles. As she learns more about mankind, however, she rebels against her protocol, boldly subverting her identity by experimenting with human instincts and sensations. Does this transformation suggest that she has developed mortal tendencies or that mortals aren’t very far removed from their synthetic counterparts?

In “Her,” Johansson’s presence is limited to that of a digital voice. As the computer operating system of a lonely flesh-and-blood divorcée (Joaquin Phoenix), Johansson creates a remarkable three-dimensional character without ever appearing onscreen, forging a bittersweet duet with Phoenix’s astonishingly nuanced performance, often viewed in close-up. Her peppy persona is straight out of the Manic Pixie Dream Girl playbook, but it all starts to dissolve as she begins to fall for Phoenix, joining him on double dates and even hiring a sex surrogate so they can share in physical contact. Since her programming allows her to know Phoenix on the most intimate level, their relationship flourishes, until it becomes clear that her capacity to grow and evolve exceeds that of any earthbound creature. Jonze’s Oscar-winning screenplay beautifully conveys how Phoenix’s own humanity is reawakened by Johansson, whose yearnings, bewilderment and consuming passions are never less than wholly relatable.

Whereas “Her” is funny and warmhearted to its very core, “Under the Skin” is rooted in the Kubrickian eeriness typified by coldly hypnotic visuals (deftly shot by Daniel Landin), an unnerving atonal score (brilliantly composed by Mica Levi) and a blurred line separating man from machine. No wonder Glazer’s fetishistic close-ups of eyes seem to have been lifted directly from the final act of “2001: A Space Odyssey.” In a spellbinding contrast to her work in “Her,” Johansson is tasked to perform primarily with her body. Any dialogue she utters, which is minimal, offers no inkling of the inner-workings of her mind. Any humanity she has initially appears to be only skin deep, as she lures her smitten, visibly aroused male victims to their imminent demise. The nudity of both genders is plentiful but hardly what one would deem as titillating. What it elicits more than anything is profound unease.

Though no plot details are ever explicitly made known, it is inferred that beneath Johansson’s flesh resides an alien life form immune to human feeling or empathy. In one of the film’s most quietly horrifying sequences, Johansson observes a husband and wife drown while attempting to save their dog in the churning waters of a beach, as their toddler son wails on the shore. The tragedy is utterly heartbreaking, but Johansson exudes chilling indifference, focusing solely on the raw meat she can capture for the obscure purposes of her formidable, motorcycle-riding boss (who takes the form of a hawk-eyed male). Only when faced with the abnormal features of her latest prey (played sans makeup by Adam Pearson) does she begin to defy her orders, perhaps questioning the purpose of her existence. Pearson recently told The Guardian that he felt his role challenges the stigma of disfigurement, and indeed it does. Rarely has a film been so frank in its unflinching depiction of the human form devoid of all safeguards and Vaseline-smeared lenses (call it the Swanbergization of modern cinema) and the effect is oddly liberating.

There is a moment here that is strikingly reminiscent of a key scene in Joe Swanberg’s debut feature, “Kissing on the Mouth,” as Johansson scrutinizes her unclothed body in a full-length mirror. She may have mastered the art of seduction, exploiting the male gaze and its hunger for female objectification, but she has little clue of how the human body and mind function. As he did in his famous extended take of Nicole Kidman in 2004’s “Birth,” Glazer maintains an intense focus on Johansson’s face and she responds by delivering the strongest work of career. It’s stunning to behold how a shot of Johansson’s saucer-eyed, emotionless face framed in dark curls can be so nightmare-inducing. She’s an empty vessel and her sultry words are merely that of an adept performer, but once she endures her first pangs of vulnerability, there’s no turning back. While Johansson’s computer operating system ultimately discovers its unlimited potential, her otherworldly temptress is doomed to stay hopelessly lost in a world far beyond her understanding.

Simply put, there is no better yang to “Her”’s yin than “Under the Skin.” These films were made for one another.

Editor’s note: I attended a 10:30pm screening of “Under the Skin” at the AMC River East 21. I sat up close in order for the screen to fill my field of vision, and it proved to be the perfect time and place to experience this immersive fever dream. Up until the lights dimmed, I was all alone in the theater. Then a woman entered the room and sat a few rows behind me. At least I hope it was a woman.