Can anyone convince me why a replicant would need tear ducts, as in the scene where Rachel goes to Dekker’s apartment and is told her memories are implants? What use would they possibly serve?
I would imagine the same use they serve in humans. Keep the eyes lubricated, remove debris etc.
This, and in some applications, a degree of verisimilitude might be desirable.
Contact lens fluid dispenser.
Correct me if I’m wrong, but wasn’t Rachael designed to be totally indistinguishable from a real human? Pris, the pleasure android, was probably designed to cry for added realism to customers who like that sorta thing.
Because “More human than human” was the Tyrell Corporation motto. How can you be human without tears?
I’d have to guess that if there were significant anatomical differences between replicants and humans, that whole “Voigt-Kampf” thing would be a breeze.
Well, apparently, replicants can pick up cryogenically frozen eyeballs and pluck eggs out of boiling water without harm. Why do you need to ask them about tortoises when you could just test their heat tolerance?
It’s beyond stupid that they don’t engineer something into them to make them easily detectable. Even if they have some sort of ethical prohibition against invasive tests.
For instance:
A weird protein that can be detected via sweat.
Make them fluoresce under strong UV light.
Put RFID chips in their skulls.
Make them exude a weird pheromone detectable by a hand held sensor or trained dog from five feet away.
Make them mildly radioactive.
Make them so they can hear or see light or sound in a certain spectrum and bombard them with it as a test.
Wire one of their reflexes wrong. IE tap their knee and they hiss.
Give them weird drug interactions, like they get teary eyed when exposed to some harmless drug.
There is any number of random things they could do to make them easily detectable yet they do none.
I still like the movie, but that’s up there with the Matrix, human battery thing.
Woo-hoo, trial by fire!
Exactly. When you think about it, a better question would be : why make robots that are indistinguishable from humans in the first place ? Or even man-shaped at all for that matter. Surely a combat bot like Roy would be better served with a number of weaponized appendages rather than hands. Same goes for the tortus-lovin’ worker bot - why give it skin when a heat and tear-resistant exoskeleton would better serve the owner’s needs ?
The only one that makes sense is Pris the pleasure bot, and frankly, if you’re willing to bump uglies with a robot, you’re either desperate or adventurous enough to do it with a weirdly designed one. With tentacles.
I know in other SF that has robots that are essentially identical to humans it is sometimes argued that having a machine that can take over any job a human can do and vice versa gives more flexibility. Or maybe humans don’t like to be reminded the robots are actually robots. Weak arguments, I know.
ricksummon they couldn’t really make beings that were insisting they were human stick their hands in boiling water, now could they?
Replicants are not robots. They are genetically engineered clones.
That’s why they have tear ducts: people have tear ducts.
Anyone who “bumped uglies” with Pris was not screwing a robot, they were screwing a cloned human who had been genetically engineered specifically for screwing a la bonobos.
The real mystery about doing a VK test on Leon was that they had their files, with pics, back at police HQ.
In general, pics, fingerprints and other biometrics kept on file after incept would have been enough.
In addition to Pris’s need to be human looking, Zhora was an assassin and looking human probably made it easier to get closer to the target.
As to the OP: The ducts actually produce a special fluid that makes replicants eyes glow in certain lighting. 
That’s never really clear in the movie; I can’t remember any technical details about the androids in Do Androids Dream of Electric Sheep?
In any case, of all the quibbles one might have regarding this movie, tear ducts seems the silliest. Obviously, the movie makes little to no sense logically. It’s one of those movies that “don’t make a lick of sense”, but work well enough in other ways to make up for it. I’d forget about analyzing it logically.
Man-shaped is easy: it means you don’t have to design special equipment for them. Man-shaped robots could use anything a man could, such as clothing, weapons, body armor, vehicles, doors, tools, factory equipment, computers, and so on. If you create an army of non-human robots you also have to create for them the specialized supporting equipment they’ll be using.
Why make them indistinguishable? No idea. It is possible that everybody in that world has some degree of genetic alteration (presuming the beings are genetically engineered clones) and that humanoid is a convenient standard; it could also be possible that the replicants weren’t originally intended to be an inferior class but laws changed over time and things ended up that way. I never read the book, and it’s been years since I’ve seen the film, though.
I did say it was only a quibble! I think it was more the use of tears to express emotion that bugged me. I understand the need for some sort of lubricant to aid day-to-day operation, but to show that an android is unhappy seems too much? Any suggestions on what the lines of code would be to produce that effect? 
In the book, Rachel talks about comitting suicide by being able to supress a nerve (vargus, perhaps?). As a replicant, she can do this, while we humans can’t. Presumably this means that she’s a genetically engineered human clone.
For a male replicant:
(
if groin.kicked.q>=0,
((sub.call ‘cry’
)
For a female replicant:
(
if emot.anger.q>=1,
((sub.call ‘cry’
(
if emot.aversion.q>=3,
((sub.call ‘cry’
(
if emot.courage.q>=8,
((sub.call ‘cry’
(
if emot.dejection.q>=2,
((sub.call ‘cry’
(
if emot.desire.q>=5,
((sub.call ‘cry’
(
if emot.despair.q>=2,
((sub.call ‘cry’
(
if emot.fear.q>=1,
((sub.call ‘cry’
(
if emot.hate.q>=2,
((sub.call ‘cry’
(
if emot.hope.q>=7,
((sub.call ‘cry’
(
if emot.love.q>=6,
((sub.call ‘cry’
(
if emot.sadness.q>=0,
((sub.call ‘cry’
)
In the peculiar case of Rachel, it makes a lot of sense.
But more generally, the founder of the Tyrell corporation seems personnally more interested in the act of creation (in the sense of God creating Adam) than in the production of useful and convenient tools.