How Replicants Work

Replicants are androids, or robots in human form. Created by Eldon Tyrell and the Tyrell Corporation, they can do many different kinds of work. They're especially well-suited for hard labor or jobs that are too hazardous for humans to do. Advertisements for moving to the off-world colonies promote the opportunity to own a replicant as an incentive. There are also other synthetic life forms available to those who can afford them, including snakes, fish and the owl that Deckard sees when he visits the Tyrell Corporation. The replicant, however, is the epitome of robotic life.

Genetic engineers design replicants and other robotic life forms from a combination of organic and synthetic materials. Though they are designed and built as machines, to some extent they grow organically.

Tyrell's Nexus series replicants, brought to market after the turn of the 21st century, blur the line between humanity and robots. The most recent model, the Nexus 6, is stronger and smarter than the engineers who created them. Nexus 6 androids are almost indistinguishable from humans, except for one major difference -- they were designed to have no emotions. Because of their sophistication, however, Tyrell's engineers expected replicants to develop emotions on their own. The Nexus 6 developers built in a four-year life span to counteract the androids' ability to adapt.

However, this plan was only marginally successful. After a bloody uprising off-world, replicants are illegal on Earth -- but that doesn't stop them from trying to reach the planet. Unfortunately, the six that jumped the shuttle for Earth are all trained for combat, which makes them particularly dangerous. One of them dies in an electrical field as the group attempted to break in to the Tyrell Corporation. We know the identities of only four more:

What they want is simple: a longer life -- more time than the four years they've been given. As with most self-aware, living beings, they don't want to die.

Despite the prohibition on replicants, these six are not the only replicants on Earth. Rachel, who works at the Tyrell Corporation, is an experimental model even more sophisticated than the Nexus 6. It has a set of implanted memories, based on those of Tyrell's niece. Fake memories, Tyrell believes, make it easier for the androids, who are less experienced emotionally, to cope with their emotions. Having implanted memories will also make replicants easier for humans to control.

With the hazards replicants pose to humankind, why would the Tyrell Corporation continue to make them? One reason is that they still sell well among people off-world. The company also wants to improve upon its work, trying to achieve its motto: "More human than human."

Escaped replicants created the need for a whole new type of law enforcement. Next, we'll learn more about blade runners and what makes them tick.

A blade runner is a police officer charged with killing, or "retiring," replicants. Of course, blade runners don't want to take a human life mistakenly, so they test their targets first. The Voigt-Kampff test measures involuntary biological reactions. First, the blade runner sets up his equipment, which monitors physical signals like muscle movement in the subject's eye. Once everything is ready and the subject sits still, the blade runner asks questions designed to touch on the subject's morals -- questions which should produce a noticeable emotional response. The machine works a little like a lie detector, measuring subtle changes in a subject's blush response and eye motion.

Since real animals are extremely scarce, blade runners ask questions that involve hurting or killing animals, which would produce a detectable emotional response in humans, but not in replicants. At least, that's the theory.

­The Voigt-Kampff test can identify Nexus 6 replicants within 20 to 30 cross-referenced questions. But more sophisticated replicants may pose a greater challenge. It takes more than 100 questions to identify Tyrell's assistant Rachael as a replicant. With its implanted memories, Rachael truly believes that it is human.

Once the blade runner identifies a replicant, it's sure to try to defend its own life at all costs. Replicants can be aggressive killers, so a blade runner's job is extremely dangerous. So why do they take on the job? Mostly, it seems that no one else wants to --even Deckard quit at one point. His old supervisor Harry Bryant forces him back into service, though, when Bryant's best blade runner, Dave Holden, is shot by one of the escapees, and the other four killers are still on the loose. Deckard is simply Bryant's best chance of taking down the four "skin jobs" before they embarrass him and the police department.

"Blade Runner" is set in a futuristic world, but the idea of androids that are virtually indistinguishable from human beings isn't all that far fetched. Next, we'll look at some of today's uncannily humanoid robots.

Engineers have been working on androids for decades, but you can't visit your local department store to buy an android butler for your home. Yet.

For many years, Honda has been working on a sophisticated android, the Advanced Step in Innovative Mobility, or ASIMO. It can walk by itself and even climb stairs. As advanced as it is, though, ASIMO's artificial intelligence is somewhat limited. It can recognize faces and voices and is capable of doing helpful tasks around the home, such as turning on the lights and carrying items.

Repliee Q1Expo is an android developed by professor Hiroshi Ishiguro of Osaka University. Like the replicants in "Blade Runner," Repliee Q1Expo closely resembles a human. It has soft silicone skin, eyelashes that move and a set of 42 actuators in its upper body that give it a range of motion [source: BBC] It even has motors that make it appear to "breathe."

Ishiguro didn't stop there. In 2007, he introduced the world to … himself. Actually, it was his doppelganger, an android named Geminoid that looks just like him. Ishiguro can see through its eyes and talk through its internal speaker. Like Repliee Q1Expo, its chest rises and falls in breathing motions.

Don't be too surprised if you find Geminoid a little creepy. Dr. Masahiro Mori theorizes that we're initially drawn to robots that seem more human-like, but once they get too human, we start to become repulsed. He wrote about this "Uncanny Valley" theory for the magazine Energy in 1970 [source: Android Science].

You might be surprised at how well a replicant can fool people into believing it's really a human. On the next page­, we confront the question that has bothered "Blade Runner" fans for years: Is Deckard a replicant, or is he human? You may be surprised to know the answer.

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If you watched the original version of "Blade Runner," you would see no overt clues that suggest Deckard might be a replicant. At the end of the movie, Deckard and Rachel get in the car and drive. Deckard's voiceover tells us that the two escape and that Rachel -- remember, Rachel is an experiment -- will live as long as humans do. They live happily ever after, and there's no reason to question Deckard's humanity.

But the Director's Cut and the Final Cut include new scenes that the original didn't, including a completely different ending. Earlier in the movie, Deckard daydreams of a unicorn. Gaff, who works with the police, has been leaving origami animals near replicants' rooms. At first, it seems like just an odd hobby, but as Deckard and Rachel begin their escape in the Director's Cut and the Final Cut versions of the movie, Deckard finds a paper unicorn on his way out of the apartment. He then knows that the unicorn daydream is a planted memory, and also that the police know what he is. Now instead of the happy ending, both Rachael and Deckard are on the run. In interviews surrounding the release of the Final Cut, Scott has said that Deckard is definitely a replicant.

This presents us with some serious questions:

For the police department, allowing Deckard to chase the other escaped replicants makes sense. They don't have to send a human into a dangerous job. But Gaff's paper unicorn suggests that Deckard won't be allowed to escape retirement now that he's taken care of the other replicants.

"Blade Runner" was based on a 1968 novel by Philip K. Dick called "Do Androids Dream of Electric Sheep?" In the novel, Deckard is not a replicant. There are many clues: He has a wife named Iran, and he owns a Penfield mood organ that he uses to adjust his moods. He also believes, or tries to believe, in the mass-media religion of Mercerism.

Still, he isn't convinced of his own humanity. To be sure he isn't an android, Deckard has a fellow bounty hunter hook him up to the Voigt-Kampff equipment and ask him how he feels about killing androids. At the thought of killing androids, especially female androids, he has an empathic response, which shows his humanity.

Both the book and the movie deal with what it means to be human. In their own interpretations on the story, Ridley Scott and Philip K. Dick come down on the opposite sides of the fence when it comes to Deckard's humanity. We'll look at how the book evolved into a film in more detail on the next page.

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In Philip K. Dick's novel, "Do Androids Dream of Electric Sheep?" Earth is ravaged after World War Terminus (WWT). Dust from the war begins a plague that exterminates almost all animal life on the planet. No one knows who started WWT, or even who won the war.

Those who are still alive began emigrating off-world. Most people are permitted to leave the planet, though some with lower intelligence quotients -- called "chickenheads" or "antheads" -- must stay on Earth to avoid contaminating human heredity. Those who stay behind, even people of normal intelligence, run the risk of being called "biologically unacceptable" -- though some stay anyway, perhaps because they simply don't want to leave their homes.

Replicants -- simply androids or "andys" in the book - are created to be "synthetic freedom fighters." Their military background might explain some of their willingness to kill. Once the war is over, the U.N. mandates that all emigrants are entitled to an android to take with them to the colonies.

Genuine animals, being highly rare, are highly prized and hard to afford. Deckard owns an electric sheep, and one of his reasons for wanting to retire his list of android targets, each of which nets him a $1,000 bounty, is to earn enough money to pay for a real animal.

Screenwriter Hampton Fancher adapted the book into a script called "Dangerous Days," and though Ridley Scott initially turned it down, he took on the project after several months' consideration [source: Greenwald].

Upon its release in 1982, "Blade Runner" had a tough time finding an audience. Budgetary concerns drove the filmmakers to make some changes to the movie, and these changes may have made it difficult for audiences to relate to the film. It's also possible that Harrison Ford fans, who had just seen him in the more light-hearted adventure "Raiders of the Lost Ark," may have been expecting a similar movie. Whatever the reason, Blade Runner was retired as a box-office failure.

That might have been the end of it, if not for its cult following. The movie came out on home video. Then a Warner Brothers executive found a print of Scott's original cut, which the studio lent to a theater showing a 70mm film festival [source: Kaplan]. The showing attracted large crowds who wanted to see Scott's original cut. Fueled by this success, Warner Brothers released the Director's Cut in 1992 with some of the missing material.

To commemorate "Blade Runner's" 25th anniversary in 2007, Warner Brothers is releasing a Final Cut. The movie is essentially the same as the Director's Cut, but has been remastered with 5.1 audio and restored special effects. At 8,000 lines per inch, the digital scan of the movie is four times the resolution of other movie restorations [source: Kaplan]. The five-DVD special edition, scheduled for release in December 2007, includes five versions of the film, including a work print. It also features a documentary and a disc of other bonus content. There should be more than enough here to keep even the biggest "Blade Runner" fans happy -- unless they'd prefer the Ultimate Collector's Edition, which comes in a replica Deckard briefcase and includes a piece of the film encased in Lucite.

­On the next page, you'll find more information on androids and related topics.