Eugenics is a set of beliefs and practices that aims at improving the genetic quality of the human population.
Obviously it is a hot-button issue. Most groups become hysterical when you suggest limiting their right to reproduce (especially if said group fears they will slip from being the majority to being the minority).
They get even more hysterical when they are prevented from reproducing by being put to death.
However there are other troubling questions. The main one is exactly what sort of measuring standard are you using to define "improved"? Almost as troubling is "who decides the measuring standards, and who does the measuring?" Obviously those in power can abuse this as a nasty form of ethnic cleansing.
More innocently, harm can mistakenly be done. For instance, sickle-cell anaemia is a genetically caused disease which occurs when the person inherits two allele of the sickle cell trait. People suffering from it rarely live past age 60. So that allele should be eugenically eliminated, right? Wrong! People with one allele are resistant to the even more deadly disease malaria. In this case, using eugenics would do more harm than good. The same holds true for the cystic fibrosis allele and cholera.
There is also the fear that such manipulation will reduce genetic diversity thus leading to inbreeding depression. In Beyond This Horizon by Robert Heinlein, genetic selection for increased health, longevity, and intelligence has become so widespread that the unmodified 'control naturals' are a carefully managed and protected minority.
Finally there is all those hideous overtones of Nazi Germany.
A milder form of eugenics is when the decision is made by the parents, not the government. You generally see this in science fiction with in vitro fertilization and a doctor giving the parents genetic counselling. The doctor gives the parents a list with check-boxes so the parents can chose what traits they want in their offspring, and advises them to omit obvious genetic diseases. The choices are fed into the machine, there is some quick genetic engineering on the zygote, then it is ready to be implanted (or popped into the artificial womb). See the movie Gattaca.
There are many ways to implement eugenics.
Quote Brain Wave has been moved here.
A concept that appears in science fiction once or twice is that "humans have stopped evolving", specifically technology and medical science have drastically hindered the process of natural selection. For instance, in primitive times a person with the genetic disease Phenylketonuria probably would not be able to survive long enough to reproduce (natural selection will prevent passing on the genetic disease). But currently modern medicine can detect the disease in newborns, and treat it with a special diet. In other words the person would survive long enough to pass it on to their offspring, thus thwarting natural selection.
Sir David Attenborough stated "We stopped natural selection as soon as we started being able to rear 95–99 percent of our babies that are born." Others have pointed out that while that might be true of 1st world countries, it is far from being true for the entire world.
In the Alan E. Nourse novel The Bladerunner (no relation to the movie of the same name) the world of the future has free, comprehensive medical treatment is available for anyone so long as they qualify for treatment under the Eugenics Laws. Preconditions for medical care include sterilization, and no legitimate medical care is available for anyone who does not qualify or does not wish to undergo the sterilization procedure (including children over the age of five). The ideas is to stop thwarting natural selection.
Others say humans are indeed still evolving, all we have done is shifted a large number of selective forces. While modern medicine has averted many biological cause of natural selection, one can see many new versions of natural selection by just perusing the Darwin Awards. In other words: deadly diseases has been replaced by Jackass.
A tangentially related concept appears in the Cyril Kornbluth short story The Marching Morons (which later inspired the movie Idiocracy). In the story, married couples who are intelligent tend not to have children, while unintelligent couples breed like cockroaches. After several hundred years of this, the average intelligence is what we would currently call an IQ of 45. The few intelligent people have no idea how to stop the collapse of society, but lucky for them a con artist who had been in suspended animation for 300 years has an answer that is effective (abet draconian).
The main flaw with the story is that the possibility of genetically breeding for stupidity is unproven.
The vast majority of mutations either [A] have little or no noticeable effect or [B] kills the embryo before it can be born. The process of evolution is advanced by zillions of tiny mutations over zillions of generations, culled by the relentless forces of natural selection.
No, exposure to radiation will not turn you into a mutant. But if your gonads are irradiated, your future children might be.
Early science fiction authors either didn't understand mutations or found the actual process incredibly boring. So they jazzed it up.
They frantically waved their hands and breathlessly announced that mutation could lead to the Next Stage Of Human Evolution™ !
This concept contains two ignorant fallacies for the price of one. First off it makes the ridiculous assumption that there are "levels" of evolution (measured by what metric, pray tell?) then it compounds the stupidity by postulating that evolution is working towards a specific goal ("orthogenesis") and you can use these non-existent evolutionary levels to measure the progress to the non-existent goal. The tell-tale sign of the latter is the phrase "more evolved."
In reality, the only "goal" of evolution is for the organism to be able to survive and thrive in whatever the current conditions happen to be in this geological epoch. Since conditions change with time, the goal of evolution is a moving target.
Early SF writers who were evolution-theory morons assumed that "intelligence" was the goal of evolutionary progress, the "ultimate life-form" at the top of the evolutionary ladder. The ultimate intelligent life-form was some sort of giant brain. Examples include the Arisans from E. E. "Doc" Smith's Lensman series.
This would lead more evolved females to demand Cesarean section. You see the relatively large size of the human baby's head is the reason why of all the species on Terra, humans are pretty much the only ones who suffer painful child birth. The evolution of a larger pelvis has not kept up with the evolution of larger baby heads.
Latter writers assumed that the goal was a set of superhuman abilities (you know: super-strength, advanced intelligence, immunity to various lethal things, and of course psionic abilities). Examples include Adam Warlock. Others cut to the chase and postulated that the end goal was to evolve humans into energy beings. Examples from Star Trek include the Organians, the Q, and arguably the Melkot, the Thasian, the Metrons, the Medusans, and the Zetarian.
The "levels of evolution" nonsense also lead to nonsensical stories where radiation from nuclear testing creates a crop of mutant children all with the same mutation. In reality mutations are more random than Pi. Not all such stories have this flaw, but there are enough to be really annoying. The only way to get lots of mutants with the same random mutation is if they share a common ancestor.
The stupid writers also got the mechanism wrong. In reality if somebody was exposed to a mutagen, their future offspring might be mutants because the DNA in the germ cells got mangled prior to procreation. But the writers were under the misapprehension that the mutagen would transform the poor exposed person into a mutant on the spot, much like the way cosmic ray exposure created the Fantastic Four. This erroneous concept was apparently created by Hugo de Vries in his 1901 story Die Mutationstheorie.
Mutants are not just people either, don't forget the radiation-spawned giant ants in the movie Them!.
None of this is scientifically accurate, but it is very exciting reading.
In Edmond Hamilton's 1931 story The Man Who Evolved, the concepts were twisted for a shock ending. The mad scientist Dr. John Pollard figures out that cosmic rays are responsible for evolution (sort of true) so exposing a person to concentrated cosmic rays will rapidly evolve them to the next stage of evolution (nope, author is unclear on the concept, it will just fry them to a crisp). With each treatment his brain becomes larger while his body becomes more spindly. At the next to the last stage he is nothing but a huge brain feeding on telepathic energy. Unfortunately for him the final stage is a pathetic primitive single-celled organism. Because apparently the levels of evolution are arranged more as a circle than as a rising staircase.
After 1945 science fiction writers finally got it through their heads that radiation would cause you to have mutant children, but not grant you any unusual powers apart from a drastically shortened lifespan. But they were still stuck on that goal oriented evolution nonsense.
The authors did however invented a brand new trope: a world wide rise in the number of mutants born due to either nuclear testing or in the apocalyptic aftermath of a nuclear war. "Children of the Atom" so to speak.
In science fiction, mutants from low level rises of background radiation due to nuclear testing tend to be superior beings with super powers. The X-Men and Perry Rhodan's Mutant Corps fall into this category.
Post-atomic-war mutants on the other hand tend to be pathetic cripples with misshapen bodies and the wrong number of limbs. In Forrest J. Ackerman's shaggy-dog story The Mute Question, the muties have a proverb: two heads are better than none.
The muties of Heinlein's Orphans of the Sky fall into this category, though in this case the radiation is not from an atomic war. As it turns out the mutie Joe-Jim also has two heads.
In the X-Men stories there is often deep-seated prejudice against mutants, since average humans have the not unreasonable fear that mutants will supplant them. Draconian anti-mutant laws are passed, and periodically there are attempts at mutant genocide. Which just goes to show what idiots average humans are. Especially given the stupendous superpowers possessed by mutants and how angry they become when you try pulling that "final solution" atrocity on them.
There is also plenty of "mutants are evil" garbage in John Wyndham's The Chrysalids. Take a post-nuclear apocalypse community with about Amish levels of technology, mix in an oppressive religion with a paranoid fear of the new, and you have a formula for a real eugenic nightmare. Mutations are considered to be "Blasphemies" and must be either killed or sterilised and banished to the Fringes.
In the Perry Rhodan novels, Terra discovers that the solar system is surrounded by highly advanced interstellar empires that would love to annex the planet. He needs an ace-in-the-hole or Terra is doomed. The Mutant Corps is a team of mutants with psionic powers which the alien empires cannot cope with. The 18 founding-members were mostly Japanese who were born shortly after the atomic attacks on Hiroshima and Nagasaki. The X-Men are sort of the Marvel comics version of Perry Rhodan's Mutant Corps, since X-Men issue #1 came out about two years after Perry Rhodan volume 6.
The archtypical superhuman mutants are the Slans from the eponymous novel by A. E. van Vogt. Every subsequent novel with "Homo Superior" mutants owes something to the Slans (though the novel is sadly unknown nowadays). When it came out, science fiction fans embraced the concept. This is because they naturally figured that they were Slans. The fans started using the pejorative term "mundane" for non-fans, sort of a science-fiction-fan version of the term "Muggle." A house or building where lots of SF fans lived was called a "Slan-shack."
There are a couple of science fiction novels dealing with mutants and galactic empires. They imply that mutants tend to appear when an empire is in the "decline and fall" stage. In his immortal Foundation and Empire, Isaac Asimov has the mutant the Mule appear during the Dark Ages after the fall of empire. In Andre Norton's Star Ranger the historian mentions that the current time of galactic empire collapse is when "change mutants" make their appearance.
Other novels mention dark rumors about how mutants with dread psychic powers are born on those planets beyond the rim of the galactic empire. An example is John Brunner's Altar On Asconel.
In Jack Williamson's Seetee Ship and Seetee Shock, the children of asteroid miners occasionally are born with abilities useful in the space environment. Rob McGee is immune to radiation, and has an ability to sense gravitational masses. This allows him to navigate the asteroid belt with relative ease. McGee is the first evidence of asterites evolving into humans suited for living in space.
In an Uplift situation, the entire point was to engineer an animal species into a fellow intelligent race. Things are marginally less tense due to the fact that no attempt is being made to keep the animals enslaved. But things are still tense because of the fuzzy gray line separating "lab animal" from "enslaved sentient." How do you decide at what point the animals cross the line? And who does the deciding? Do you free the slaves? And is it a bad thing if the animals jump the gun and start a slave revolt if they disagree over which side of the gray line they are on?
Though in David Brin's science fiction universe when Species A uplifts an animal into Species B, by galactic law Species A has the right to hold Species B in indentured servitude for a mere 100,000 years. As payment for the cost of uplifting Species B.
In The Ballad of Lost C'Mell by Cordwainer Smith, the "underpeople" are all uplifted animals, and are all enslaved. C'Mell is an uplifted cat (you can tell by the C in her name) who during the story helps her fellow underpeople to gain more civil rights.
In Mrs. Frisby and the Rats of NIMH (made into the movie The Secret of NIMH) the bumbling morally-bankrupt scientists are just playing around with giving animals enhanced intelligence. It comes as a very rude surprise when the animals become intelligent enough to escape the tortures of NIMH. The scientist panic and launch a dragnet to find and kill the animals but they get away into the countryside.
And of course there will be some evil bastards who uplift animals with the specific purpose of creating a race of slaves, generally for use as a private army. These are usually genetically engineered or implanted with brain electronics to ensure they will never revolt and inflict well-deserved revenge upon the ruling evil bastard. The bastard might not even start with animals. In the Lord of the Rings Morgoth took elves and mutated them into orcs. Sometimes two sets of evil bastards do this to each other: in Jack Vance's The Dragon Masters the humans and the dragons of the planet Aerlith have captured their opponents and bred them into combat slaves and beasts of burden.
The earliest known example of the uplift concept was H. G. Well's The Island of Doctor Moreau.
Other notable examples:
- L. Sprague de Camp's "Johnny Black" stories (beginning with "The Command")
- Olaf Stapledon's Sirius
- Cordwainer Smith's Instrumentality of Mankind series features the "Underpeople:" various uplifted animals held in slavery. Most prominent is C'Mell, where the "C" denotes "uplifted cat".
- David Brin's eponymous Uplift series. The amusing part is apparently every species in the galaxy arose from uplift, except for human beings. And of course the legendary sacred Progenitors.
- Robert Heinlein's Jerry Was A Man.
- In the Marvel Comics Universe, the High Evolutionary's main goal is uplift.
- In Arthur C. Clarke's 2001 A Space Odyssey, humanity was uplifted from the apes by the star god monolith makers.
- In Howard Taylor's Schlock Mercenary many of the mercenaries are uplifted species, such as elephants, gorillas and polar bears.
And many others.
In pulp scifi, Uplift's dark sibling is the dread horror of induced atavism. I specify pulp scifi because the concept is total bovine excreta. I mention it just in case you run across it.
It generally takes the form of some sort of drug or ray that will cause the victim to gradually "de-evolve" down the "evolutionary path" (which should alert you right away that this is total nonsense. Because there ain't no such thing as an evolutionary path.) The victim will first transform to become brutish, then turn into a pre-human ape, then into a giant lizard, and so on.
This is some science-fictional method to restore a person's youth, to remove the ravages of age. A sci-fi version of the Fountain of Youth. And you can bet your last rocket that TV Tropes has a page all about it.
Obviously, aging movie stars would kill for access to such technology.
And keep in mind that in fiction such treatments do not necessarily prolong a person's lifespan. They may well die at about the same age they would have ordinarily, they'll just leave a good-looking corpse. Or maybe not. In stories traditionally a person granted eternal youth will instantly have their body shrivel up to match to their chronological age upon death.
In the Greek myth, this is the bit that the goddess Eos left out of the fine print when took Tithonus as her lover, and asked Zeus to grant him eternal life. Zeus noticed she had forgotten to also ask to grant eternal youth, so he decided to be an asshat and omit it. Poor Tithonus lived forever; but grew more aged, feeble, and pained with each passing year. He begs for death as Zeus snickers in the background.
On the planet Cerberus, a semi-sentient nano-organism imbues colonists with a strange power. If two people fall asleep while within a few meters of each other, their electrical brain patterns swap bodies. As far as the people can tell, they woke up in the other's body. This is considered normal, and there is a gizmo that can identify who is in what body.
The aristocrats use this in a nasty fashion. They make sure they have good healthy children. Then when they feel like their current body has become too old, they forcibly switch bodies with their healthiest 20 year old offspring. They now have a fresh new body. The offspring is stuck in the decrepit old body, and is imprisoned or otherwise disposed of.
This is actually verging on immortality, since you can live forever if you have access to fresh new bodies.
And even though it doesn't work, in fiction the hideous Elizabeth Báthory technique never gets old.
The Micronauts was a comic book that came out in 1979, as a thinly disguised attempt to promote a line of toy action figures. However, the plot line was actually surprisingly deep. It did have your standard "Star Wars-esque rebels fighting the Evil Empire" background, but unlike Star Wars it had some motivation.
In Star Wars, the Emperor is oppressing everybody just because he is a big bad meany.
Baron Karza, the villain of the Micronauts, motivates the population to oppress themselves.
Karza developed and has a monopoly on advanced organ and body transplant technology. So Karza tells the wealthy "Do whatever I tell you to do, and I'll give you eternal life and eternal youth."
Naturally the wealthy fall over themselves to do Karza's bidding.
The lower class of society work at menial jobs. They can obtain "life credits" (redeemable at Karza's medical labs) by  as a part of their minuscule salaries,  by selling their limbs and internal organs, or  enlisting in Karza's Dog Soldier army and becoming less-than-human.
Well, technically there is  winning life credits at Karza's casinos, but everybody knows that the house always wins.
The underclass of society are periodically captured by Dog Soldiers sweeping the slums and sent to Karza's Body Banks. Hey, prolonging the life and youth of the wealthy aristocrats needs lots of fresh new internal organs and entire bodies. You gotta get supplies from somewhere, right?
Predictably by this time there is no middle class.
The rebels find this Frankencracy to be an intolerable situation and are rebelling. Since this is the back-plot for the entire comic book series, the rebellion faces a constant uphill battle. Otherwise the series would be over half-way through the first issue of the comic book.
"Immortality" means being partially or fully immune to dying from old age. You can still die from starvation, being blown out an airlock with no spacesuit, or being drilled between the eyes by a laser rifle.
"Invulnerability" on the other hand is being remarkably difficult to kill with clubs, swords, or firearms. Having a body composed of diamond, Wolverine-levels of regeneration, resurrection like Count Dracula, that sort of thing.
Having one of these abilities does not necessarily mean you have the other. TV Tropes calls having both Complete Immortality.
Immortality is a perennial favorite, since practically nobody wants to die. I'm not kidding. The concept dates back at least to the The Epic of Gilgamesh (circa 2100 BCE) the earliest surviving great work of literature.
The techniques vary, some are from machines, some are from exotic drugs.
For one thing, unless you pass laws about term limits and maximum age of political office, you've suddenly got a gerontocracy on your hands.
For another, if the lifespan lengthens to past about 500 years or so, you'd better limit the number of children allowed to a family or overpopulation will make a reappearance. Once you have death control you have to have birth control or you'll be standing on Zanzibar. Logically, the reason any species has the ability to procreate is because they are mortal. Otherwise the species would go extinct. Remove the mortality and you remove the need for procreation.
Naturally, this becomes less acute if immortality is not for everyone, but just for a privileged few. Even if that spoil-sport Immanual Kant says it is immoral to do something that is only bad if everybody does it.
TV Tropes calls this the Immortal Procreation Clause: The fertility of a species is inversely proportional to its lifespan. Thus, as a species approaches immortality, their birth rate approaches zero. This can be the result of natural infertility, or because they don't want to be up to their eyebrows in squalling babies so contraception is employed.
On a broader level there is the problem that reducing the birth rate also reduces the evolution rate of the species. No children, no evolution. Keeping in mind that the invention of modern medicine has already put a damper on evolution.
There are other problems with immortality, over and above the literary motive of saying it is just plain immoral for some reason or another.
A couple of time the science fiction author wanted to make the immorality rather stark black-and-white. The immortalty treatment requires the death of another person (sometimes of an alien species but still...). Stories include Ben Bova's Stars, Won't You Hide Me? and the Babylon 5 episode Deathwalker.
It has often been noted that in society "the rich get richer." At least nowadays the super rich eventually die so their wealth is divided among the children. But an immortal rich person is just going to keep getting richer. The same goes for a politically powerful immortal. They keep getting to be more powerful and are never removed by death (well natural death at any rate, I'm sure the descendants will be busy hiring assasins).
In "The Martyr" by Alan E Nourse the invention of immortality puts the breaks on progress. They can only give the treatment to 500 carefully selected people each year, but after a couple of decades the effect is quite noticeable. The starship project stalls because there is no motivation to get things done in a timely fashion. Since each treatment adds another sixty years to your life, why not spend yet another year on starship testing just to be absolutely sure? And the politicians start becoming permanent fixtures. With each decade they just add to their repertoire of dirty political tricks, new novice politicians don't stand a chance. Stagnation.
The "lack of pressure" drawback is also featured in Between The Strokes Of Night by Charles Sheffield, in chapter 29.
In Isaac Asimov's The Naked Sun the Spacers have a lifespan of 400 years or so. They become hypercautious and terrified of disease, since they have so many more years to lose than a filthy Earthman with their three-score and ten. Spacers are also unbelievably conservative and resistant to change.
In many science fiction stories the supreme enemy of an immortal being is boredom. After ten-thousand years or so it is almost impossible for an immortal to find anything new, or even anything they've only encountered five hundred times before. In The Lost Worlds of 2001 Arthur C. Clarke said "There were few things that an immortal welcomed and valued more greatly than surprise; when there was none left in the universe, it would be time to die." This is explored in Raymond Z. Gallun's The Eden Cycle and Michael Moorcock's Dancers at the End of Time sequence where the protagonists must go to extreme and absurd lengths to keep ennui at bay.
In the role playing game The Burning Wheel, the Elves are immortal. As a consequence they are elegiac, tragic, and constantly grief-stricken. After all, the longer you live, the larger the number of friends you have seen die (generally in combat). Us older people have experienced a mild version of this: the older you get, the more of your beloved TV and movie actors you loved from childhood depart for that big silver screen in the sky. Especially in the year 2016.
In the movie Pirates of the Caribbean: At World's End Captain Teague tells Jack Sparrow: "It's not just about living forever, Jackie. The trick is living with yourself forever."
In Glen Cook's The Dragon Never Sleeps people periodically make brain recordings as a backup. If they are killed, a new cloned body can be quickly warmed up and impressed with the latest recording for an instant resurrection. Sort of like playing a computer role playing game and saving the game periodically in case your player character unexpectedly dies. In fact, if the body of the dear departed has a brain that is not too damaged, it can be scanned to proved a back up more recent than the last brain recording.
However, since the powerful Houses in the novel are about as peaceful and innocent as the ones in The Game of Thrones, assassination is commonplace. So much so that a specialized weapon was developed: the skull-splitter. It fires a bullet of compressed metallic sodium which will totally fry the victim's brain beyond all hope of scanning. In other words is it a weapon specifically optimized to screw up the target's resurrection. Granted, it only eliminates the person's memories between now and the last backup recording, but that can be useful in carefully crafted political plots.
But immortality is not all bad. It comes in handy with slower-than-light space travel. Or even faster-than-light, the "anti-agathic" immortality drugs of James Blish's Cities In Flight series were developed because star travel at 20c still consumes a huge chunk of one's lifespan. In Robert Forward's Rocheworld, the drug No-Die slows the aging process to one-fourth the normal rate. Unfortunately it temporarily lowers intelligence by roughly the same factor. It is needed because the STL laser light-sail is going to take 42 years to fly to Barnard's Star, and a crew of retirement-age astronauts would do an exceedingly poor job of exploration.
Science fiction authors are also fond of teasing the reader about immortality. In Whatever Happened to Corporal Cuckoo? by Gerald Kersh the protagonist meets the eponymous Cuckoo who was born in 1507. He suffered a severe head trauma, and was treated by mad doctor Ambroise Paré with The Digestive (a concoction of oil of roses, honey, turpentine, and egg whites). This makes Cuckoo both immortal and invulnerable. Cuckoo wants to buy a farm to produce the needed ingredients so he can make a fortune selling The Digestive.
The protagonist torpeodes Cuckoo's plan by pointing out the wide variations in bee honey, eggs, et al. The chances of recreating the formula by using such organic ingredients is zilch.
Why fool around with messy recreational drugs when you can use more high-tech methods? Nirvana is just a wire away.
Like all communication technologies through history, this is eventually used to create pornography. One of the more irresponsible team members secretly uses the machine to record a sexual encounter with his girl friend. Things get grim when he shares the tape with a colleague. Said colleague does something very stupid. He clips out just the part of the tape containing the actual orgasm, and splices it into a continuous loop. Then he plays it. He is found a day later in his home still hooked up to the still looping tape. He's alive, but the sensory overload has prematurely aged his brain.
However, things get grimmer when the government seizes control of the project. It starts applying the technology to weapons control, brainwashing, and psychological torture.
But the really weird stuff only happens after one of the researchers realizes that she is having a fatal heart attack, and records her own death...
Further in the future, a manipulative alien figures out how to make a beamed energy weapon that will stimulate the target's pleasure center, at a distance and with no electrodes needed. This fiendish device is called a "tasp." Irresponsible people think it is a big joke to use the tasp on some random person they see on the street. The slang phrase for this activity is "Make Your Day."
Since they are not using any controlled substances, the police cannot arrest anybody doing this since it is not against the law. Actually the police have no way of even detecting if people are actually doing it, other than the smile on their faces.
Tales of technology turning civilizations into worthless decadent people dates back at least to H. G. Well's The Time Machine (1895), with the pathetic Eloi and brutal Morlocks. Things have only accelerated since then. Some such stories have become quaint, overtaken by events. E. M. Forster's The Machine Stops (1901) has people living in little cubbies, their only activity is using a sort of video conferencing machine to communicate with others. Sounds to me like present day guys living in their mother's basement, doing little else besides trolling Facebook and Twitter.
I remember people predicting the downfall of Western Civilization due to the invention of the TV remote control. Just think about a generation of couch potatos too lazy to get up, walk to the TV set, and change the channel. Actually, such predictions were not far off the mark.
The idea is that every person will be given a computerized device at birth which will will stay with them, teaching them and learning their owner's personality. They could even take over dull routine tasks like answering the telephone. They would also record more or less everything their user sees, hears, and otherwise experiences for their entire life. Sort of a backup memory.
Stealing such a device would be tandamount to stealing a person's entire life. Example: movie Taking Care of Business, except more so. There will also have to be laws against the police subpoenaing a person's electronic companion, something along the lines of spousal privilege.
Also, the device could assist a child while growing up; example: the nanotechnology educational book given to Nellodee in The Diamond Age. Such a device could also mold and brainwash a child; example: I Always Do What Teddy Says.
With respect to an electronic companion substituting for you over the telephone, there was a recent article titled: Tired of texting? Google tests robot to chat with friends for you. The Fark.com version of the headline was "Google tests robot to chat with friends for you, so you could be dead for weeks before they know it"
IQ DRUGS AND MACHINES
Drugs that amplify intelligence (temporarily or permanently) are called Nootropics (aka smart drugs, memory enhancers, neuro enhancers, cognitive enhancers, and intelligence enhancers).
Examples from science fiction include R-47 from Gordon Dickson's THE R-MASTER, “VC” (viral coefficient) from John Brunner's THE STONE THAT NEVER CAME DOWN, "Hormone K Treatment" from Ted Chiang's UNDERSTAND, Methuen Treatment from L. Sprague de Camp's THE EXALTED, NZT-48 from the movie LIMITLESS and CPH4 from the movie LUCY.
A Brain-Computer Interface replaces the standard interaction between person and computer via monitor, keyboard, and mouse with something a little more intimate. The comptuter is connected direcly to your brain via implanted electrodes or something like that. Imagine a USB port in your skull. See the above link for details.
In the intelligence amplification category, such an interface can allow such IQ accelerating techniques as querying Google at the speed of thought and providing a math coprocessor for your brain.
In William Gibson's Mona Lisa Overdrive are datachips called "skill softs." If you need to speak Mandarin Chinese, pop in a Mandarin skill soft into the chip port on your skull. Ditto nuclear physics, cordon bleu chief, or military strategist. Skill softs for physical skills like karate, sharpshooting, and jet fighter pilot will require additional interfaces to your reflex nervous system. Skill softs are Upgrade Artifacts.
In James White Sector General science fiction novels if for instance, a human surgeon had to operate on a Melfan patient, the surgeon would be temporarily imprinted with an appropriate memory tape. This is a brain recording of an alien surgeon who is an expert in the required surgery. The trouble is the brain recording is not just the surgical skill, it is all the alien's memories. So the poor surgeon has an alien split-personality as long as they are imprinted. The memory tape is erased from the surgeon's brain immediately afterwards. Diagnosticians are entities who have such mental stability that they can hold multiple brain recordings simultaneously. They use this cross-knowledge to do original research.
The movie Brainstorm noted how such an interface can be used to record an experience on tape and play it back so another person can experience the same things. Eating a meal at a five-star restaurant, sky-diving, traveling to exotic places. Not to mention pornographic applications. They didn't go into it in the movie but such an interface can be used to directly connect two people together, creating a sort of computer assisted telepathy.
From the person's standpoint, it appears like their mind is moved out of their meat body and transferred into a computer.
From an outside view it looks more like an incredibly advanced computer program is written which can perfectly simulate your memories, thoughts, and personality. The meat person still exists, they are a little dubious about this perfect simulation software running in the computer in the next room. Yes, this opens a screaming can of flailing worms full of questions about what is identity and related matters.
This is part of the Digital Crew Concept for slower-than-light starships, since uploaded people only require a computer, they have no mass and require no consumables.
Note this can result in the extinction of the human race by Existential Risk 6.1 Take-over by a transcending upload.
In the science fiction realm, memory can become a problem if a person is immortal or very long-lived. It is unknown what the maximum memory storage capacity is for the human brain. And even if there is plenty of storage left, how do you find the particular memory you seek? Imagine trying to find a particular web-page on the internet if there was no Google or other web searcher. Each day adds a days worth of new memory data to drown in.
The mechanical solution is to use a You-Simulator, hooked up to some kind of search algorithm. The mental solution is to use mnemonic techniques, such as the Method of loci. This sort of adds an index to one's memories.
This is some sort of science fictional technique where a person learns some skill or knowledge in a half hour or so. It generally takes the form of putting on a headset, lying in a bed, going to sleep (or being drugged), and having the knowledge electronically engraved into your memory. It is commonly used to learn a new language, but sometimes more complicated knowledge can be acquired. It is sometimes called hypnopædia, or hypnopedia.
Common limitations include:
- The user is not aware of the new knowledge unless they go rooting around in their memory.
- The user has learned facts, but they need standard drills to be able to use the facts. For instance, you can learn about trigonometry, but you cannot use it without conventional math training
- It can be used for brainwashing or deep indoctrination
A nice pseudo-mystical trope is the biggest barrier to more efficiently using your mind is getting rid of false data. In the same way that your knowledge of the fact "I cannot learn calculus because my brain cannot handle math" is preventing you from learning calculus; similar non-facts are preventing you from learning telepathy, precognition, and otherwise being a Jedi Knight.
Played for laughs is when the science fiction author has their characters look down upon those benighted fools living in the 2010s who were stupid enough to think that tobacco and food high in saturated fats were bad for you; the exact opposite of what science now knows to be true. Yes, this is a TV Trope.
More seriously there are hundreds of science fiction stories where faster-than-light starships were invented only after scientists in the future discovered that Einstein's relativity was not precisely correct. Characters in the story will commonly sadly shake their heads at our current-day scientists, comparing them to scientist in the 1600s who believed in phlogiston or other obsolete scientific theory.
In science fiction, protagonists who are adults struggle to overcome the false data they have learned in order to obtain a superior mentality. In extreme cases, this is impossible, the only thing that will work is teaching the right data from the start when the individual is a small child. The classic story here is Mimsy Were the Borogoves by Henry Kuttner and C. L. Moore.
There is a tradition in science fiction stories of people pretending that they have magic powers but are actually using high-tech devices hidden about their person. TV Tropes calls this Magic from Technology. To give them their due, some use tech that is so high it invokes Clarke's Third Law, so the question of whether this is fakery or not is moot. If a technomage can point their finger and the target is incinerated by lightning, does it matter if it was done with a magic spell or with a miniaturized particle beam weapon? Incinerated is incinerated.
A related concept is Magitek.
The United States is conquered by an Asian Empire called PanAsia. But at the last moment, a hidden military lab makes a scientific breakthrough. The lab now has the secret to weapons of Doc Smithian power and other cool gadgets. Unfortunately they are only seven men in a nation occupied by zillions of PanAsia troops. What can they do?
The scientists want to start an underground rebellion. But you need large groups to spread the conspiracy, and the Empire has forbidden large gatherings. However there is one loophole: religious worship allows large gatherings. The asians know how touchy an occupied nation is about their religions.
So the scientists invent a crazy religion with ridiculous deities. The asians don't notice anything odd since this new religion looks just as inscrutable as the other US religions. The occupied populance can see this is odd, but the religious services offer a free lunch. The high tech devices can do things like cure cancer and other diseases, which also attracts "worshipers." The congregations soon notice things such as all the hymns are being to the tune of forbidden US patriotic songs. And the sermons are full of dog-whistles about undercover resistance. The priests are on the look out for particularly intelligent and motivated members of the congregation. They are vetted and recruited into the rebellion.
For "religious" reasons the priests have to wear large floppy robes with turbans, to allow more space to hide high-tech devices hidden about their person. The turbans conceal communciation devices, and a bit of tech that makes the illusion of a halo. Their sacred walking staffs are energy projectors, emitting rays that can heal, transmute lead into gold, and disintegrate. Since the staffs are important to the religion this gets around the PanAsian ban on weapons. Their belts contain a force field generator.
When the final battle occurs, there is a particularly striking image. For psychological purposes, they use a holographic feature to create the illusion of one of the priests as tall as a skyscraper, sending rays of death and destruction into the PanAsia troops.