Posted on behalf of Christof Koch

@ 2015 Universal Pictures

By and large, we watch movies to be entertained, not to be provoked into deep thought. Occasionally, a film does both. This year’s Ex Machina is one such gem. It prompted me to reflect upon the evolution of the idea of machine sentience over the past three decades of science fiction on film.

I am a long-time student of the mind-body problem — how consciousness arises from the brain. There is a conundrum at the heart of this ancient dilemma, challenging both brain science and AI; and it is well captured by Ex Machina and two other SF movies. In essence, it lies in how we can ever be certain that a machine feels anything, is conscious.

Consider Ridley Scott’s dystopian classic Blade Runner (1982). The morally ambiguous ex-cop Rick Deckard (played by Harrison Ford) is tasked with “retiring” four replicants, bioengineered androids that escaped from an off-world colony and are hiding in a dark and oppressive Los Angeles of the near future. After killing three, Deckard is saved from a lethal fall by the last, Roy Batty (Rutger Hauer). As Batty’s life runs out (his model of android lasts just four years), he delivers his justly famous death soliloquy:

I’ve seen things you people wouldn’t believe. Attack ships on fire off the shoulder of Orion. I watched c­-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time … like tears in rain…. Time to die.

These words speak to the clarity and poignancy of Batty’s memories — whether real or synthetic, lived or implanted.

Deckard’s final act is a recognition of these creatures’ essential human-like nature: he leaves his life behind and flees with Rachael, a more advanced replicant who believes herself to be human. Deckard crosses a line, at least implicitly endorsing the belief that replicants have feelings of regret, of pity, possibly even of love. (The question of whether Deckard is himself a replicant remains one of the more tantalizing in movie history.)

Tried and tested

In that sense, Batty, Rachael and their companions pass the Turing test. Introduced by the mathematician Alan Turing in 1950 to answer the question “Can machines think?”, it replaces this metaphysically loaded query with a pragmatic imitation game. If an agent can’t be distinguished from a human being, the agent passes the test.

The Turing test remains alive and well in philosophy of mind and in the annual competition for the $25,000 Hugh Loebner prize — albeit less so in university computer science departments.

Warner Brothers

Consider a version of the test focused on the question “Can a machine be conscious?” That is, does it feel like something to be this artifact? My washing machine has no feelings, but an android might well have – such as pity over the impending death of a human pursuer or pride in its own accomplishments. How would we know?

How do we know that anybody else but us is conscious? By interacting with them — asking them, “Tell me about your feelings.” Variants of this are used with non-linguistic competent individuals, whether aphasic patients, infants, or monkeys or other animals.

So, if what a machine tells us sounds plausibly human, we may act as if it too were sentient. Going by Deckard’s action in saving his beloved from doom, Rachael has passed the Turing test.

Fast forward to the 2013 romantic SF comedy Her, directed by Spike Jonze. In it, the anodyne writer Theodore Twombly (Joaquin Phoenix) downloads a new applet, Samantha — essentially an advanced version of iPhone’s Siri. It is a plausible storyline for our digitized age: a lonely guy speaks incessantly to his smartphone, who answers in a seductive voice and knows everything about him, his emails, his likes and dislikes, even his dating history. They joke, have intimate discussions; he takes her everywhere. Samantha is the last thing he speaks to before he goes to sleep and the first upon awakening.

Her eschews any significant discussion of the extent to which a computer program can have conscious feelings. Twombly doesn’t worry about such philosophical speculations; he behaves like any lover. Indeed, his passion for Samantha, who ‘lives’ in the cloud, cools after she confesses that she is simultaneously interacting with 8,316 other customers and is in love with 641 of them.

All about Ava

Enter Ex Machina, directed by Alex Garland. This intelligent and thoughtful mix of psycho-drama and SF thriller centers on a strange ménage à trois. Ava is a beauty with a difference (a phenomenal performance by Alicia Vikander); Caleb is a nerdy young programmer (Domhnall Gleeson); Nathan is a beastly, brilliant inventor and immensely rich tech-entrepreneur (Oscar Isaac).

Caleb is selected by Nathan, a recluse, to spend a week at his live-in Arctic laboratory. He introduces Caleb to Ava, an advanced cyborg whose semi-transparent skull and body reveal inner workings, including a brain that is quasi-organic in some unspecified way. It’s a twist on Blade Runner: if Caleb interacts with Ava as he would with an alluring woman – while seeing clearly that she is not flesh and blood – that would testify to Ava’s ability to convince him she has real feelings. Ava and Caleb hit it off at first sight.

Unlike Her, Ex Machina soon becomes a game of smoke and mirrors. Ava hints to Caleb that she doubts Nathan’s purely scientific motives; there are bizarre scenes such as Nathan doing a synchronized dance routine with a mute servant. Nathan’s lab becomes Bluebeard’s Castle, complete with locked rooms and heavy psychosexual undertones. Ex Machina’s ending, invoking the trope of the femme fatale, is logical, surprising and darker than Blade Runner’s.

All three films showcase how the psychology of desire can be exploited to forge a powerful empathic response in their protagonists, sweeping away doubts about the object of their longing having sentience. It’s a Turing test based on lust, each movie an excursion into human social psychology and the attendant gender power politics. Unfortunately, the movies don’t inform us whether or not Rachael, Samantha and Ava are conscious or not. Simply that the men in these movies behave as if they were.

Leaving all that aside, I have little doubt about the essential scientific veracity of these movies. Within this century, we will create artifacts that will behave to all intents and purposes as if they too shared the gift of conscious experience with us. They will pass the Turing test. Blessing or curse? Only time will tell.

Christof Koch is chief scientific officer of the Allen Institute for Brain Science in Seattle, Washingon.

For Nature’s Insight page on machine intelligence, see here. For Nature’s full coverage of science in culture, visit www.nature.com/news/booksandarts.