Humanity Is Infectious / Literature

• Subverted in The Damned Trilogy where it's a bad thing because Humans Are Warriors, not least because they are the only species who can comfortably use violence. The alien scholar Lalelelang has been studying humans for years, and in the climax of one novel is able to kill in her own defence, though the act gives her a Heroic BSoD.
• Terry Pratchett is fond of this trope.
  • In the book Thief of Time, Myria LeJean, Auditor of Reality, has been a person for so long that she got a personality and joined the Good Side fighting her former "comrades". Sadly, she commits suicide because she believes she has no place in the world she helped save. This reveals she'd become more of a person than she thought, as she then meets Death again - she'd died, and "this is the next part".
    • Her former comrades are also affected, it's just that in trying to fight it they end up with such human charactersitics as anger, argumentitiveness, and homicidal insanity, rather than free-thinking and compassion.
  • Death himself has been shown to be particularly susceptible to this, going so far as to getting fired once for being too empathetic (by adopting Susan's mother), and almost turning human himself.
  • In the co-authored book Good Omens, this happens to the angel Aziraphale and the demon Crowley as well: Aziraphale becomes a little more lax about rules and when to follow them, while Crowly develops a bit of a conscience and takes a liking to humanity. This is directly compared to cold war spies; after millennia of only dealing with their opposite numbers (each other) they feel a lot more kinship with them than they do with their official superiors.
  • Mort shows that the inverse is also true for Death- As Death neglects The Duty more and more, his assistant Mort begins to gradually gain Death's powers, mannerisms, personality, and even his voice. Apparently, Death is whoever does Death's job.
  • Men at Arms describes dogs as being wolves that have been "infected" with human traits, the good and the bad. This also leads to werewolves acting more like dogs than they do wolves.
  • Throughout the series, many creatures are described as "almost human, really", such as a Troll who lends at 300% interest per month, or Dragons fighting to death rather than submission.
  • Three words: You've been Weatherwaxed. Turns out, Granny Weatherwax's personality is so strong that it transfers into the vampires that bit her. And she doesn't become a vampire at all. (Of course, this is only one human being infectious, but she did a damn good job of it.)
  • In some of the later books, infectious humanity is treated a bit like Western imperialism; if goblins are becoming more human, does that mean they're becoming less goblin, and is that really a good thing?
• From The Dresden Files:
  • First, we have Lash, a copy of the Denarian Lasciel implanted in Dresden's Mind. She originally acts as Toxic Friend Influence trying to bring him to the dark side, but eventually is won over by Dresden and sacrifices herself to save him.
    • Lash is really a Subversion, though, because she does actually succeed in her mission to make Harry a little less human (by giving him a Hair-Trigger Temper and making him dependent on Hellfire), and she isn't really Lasciel, she's a part of Harry's brain that thinks like Lasciel, and so is just as able to change her mind as Harry is. Harry notes himself that he could never hope to convert the actual Lasciel.
  • In Proven Guilty, the Winter Lady Maeve expresses concern that her late counterpart in Summer, Aurora, fell victim to human concepts like "hearts, good, evil."
    • May or may not be an example, given we now know that both Maeve and Aurora were infected by Nemesis, which makes its infectees prone to uncharacteristic behavior that advances its goals anyway. Though it is possible that that just set the stage for Aurora succumbing to infectious humanity.
• In Liz Williams' Detective Inspector Chen series, one of Chen's friends is a demon who's developed a conscience from being around people too much. In the scene where this is first mentioned, he describes it as if it were literally something infectious he'd caught off humanity, and claims that the only reason he hasn't had it seen to is that as a minor public servant his health insurance doesn't cover it.
• Literal (and quite unpleasant) variant in Isaac Asimov's short story "Hostess". It appears that ageing and "natural" death are results of a parasitic life form, which infects all humans. Aliens don't age, and their death is either accidental or voluntarily. Except that now the parasites start infecting aliens, too...
• A nastier-than-usual version in Star Wars Legends: when the Killiks inadvertently assimilate Raynar Thul into their Hive Mind, they begin to value individual life—even though individual Killiks aren't particularly sapient and reproduce extremely fast. Next thing you know, they're trying to expand their territory like crazy, nearly precipitating a war with the Chiss.
• In Animorphs novel Visser we learn that Visser One very nearly fell into this trap when she discovered Earth, and she had a partner, Essam, who fell into it completely. In varying degrees, there are any number of Yeerks in the main series who start acting and identifying more "human" than the Yeerk Empire would want them to.
• This was the strategy used to defeat the Tyr in C.S. Friedman's The Madness Season. The Tyr were a Hive Mind alien race incapable of knowing fear, since the individual lives were worthless, or compassion, since it was unable to comprehend sapience outside of itself. However, during one stage of Tyrrish development, it becomes separated from the overmind. The humans manage to get hold of one such adolescent Tyr and teach it the notion of individuality — even going so far as to give it a name, Frederick. The winning strategy is then to get Frederick into a position where he becomes the new Overmind, infecting the entire race with fear of individual mortality and compassion for outsiders.
• In the Codex Alera, the Vord Queen starts to slide into this, ending up as an almost-Cute Monster Girl from the Uncanny Valley. She's invading Alera because her daughters in Canea are trying to kill her for being "defective." It is strongly implied that the reason that she is acting so "human" is because Tavi accidentally bled all over the mound she was incubating in, resulting in an integration of human genetic material with Vord.
• MorningLightMountain over the course of Pandora's Star and Judas Unchained as an accident of uploading Dudley Bose's personality into its brain to learn about humans. Turns out this is a bad thing because MorningLightMountain's inherent urge to expand get's augmented with things like hatred for all things not MorningLightMountain.
• This is a significant theme of Robert A. Heinlein's novels dealing with intelligent computers. It occurs first in The Moon Is a Harsh Mistress, when the computer Mycroft Holmes learns to be human (and enjoy it) through observation of those around him. Similarly, in Time Enough for Love, Lazarus Long expresses the opinion that the thing that turns a computer from merely a powerful machine into a fully sapient AI is The Power of Love — specifically, being loved and paid attention to by a human. This can then develop into full-blown desires to Become a Real Boy.
• The Man Who Fell to Earth, both novel and film, plays the idea of an alien becoming more human as a tragedy: Thomas Jerome Newton starts as an innocent humanoid alien and ends up an alcoholic, broken, trapped-on-Earth wreck thanks to human pastimes and relationships. The story averts Humans Are the Real Monsters, but we don't come out looking too hot...
• Averted in C. J. Cherryh's Foreigner (1994) series. The alien atevi experience no emotions which are forms of affection, and they never will, because which emotions an organism can experience are determined by neurological hard-wiring, and atevi don't have the hard-wiring for those emotions. Similarly, the atevi do have the alien emotion manchi, an emotion that humans will never be able to experience, no matter how much exposure they have to the atevi.
• The World War series by Harry Turtledove has cultural infectiousness going both ways. While we adopt lots of The Race's technology, and their practice of not wearing clothes and instead wearing body paint, and even their practice of calling things "hot," (similar to slang for "Cool,") we managed to introduce the Race to The Oldest Profession, drugs, and marriage. It's more difficult to see the contamination of the Race's culture, though, because of how slowly their society moves.
  • Right up until Homeward Bound, where we see members of The Race wearing wigs, which comes as something of a shock to both the human protagonists and their 'mission to earth' opposite numbers.
• In the Starfleet Corps of Engineers stories, P8 Blue, an insectoid alien, finds that her belief systems are influenced by the humans she works with. She begins to find an interest in history where her people usually ignore it, and even feels slightly maternal towards her larvae, being a little sad when she drops them off at the childcare centre, never to see them again.
• In Ray Bradbury's The Martian Chronicles, the Martians (who have psychic abilities of some kind) gradually become infected with human memories to the extent that their entire culture goes insane and is pushed to the point of extinction.
• In Leviathan Wakes, Miller is able to negotiate with Eros because the protomolecule which infected Julie Mao used her personality as its foundation.
• In David Brin's The Uplift War, one alien is studying a human language with derision. Take that messy term "accident" — why the humans even had a saying, "There are no accidents."
  At the end of the work, while reflecting on what resulted in their defeat, and how things could have gone differently, the alien realizes that nonetheless "there are no accidents."
• Legacy Of The Draconica: Spending ten years in a human's mind absorbing emotions and watching him interact has allowed a mindless weapon (Mordack) to develop a sense-of-Self.
• In Blue Rabbit, Chloe first comes into the human world unwillingly, but after spending some time there and making friends with human teenagers, she decides she wants to stay and become human. Riven, who like Chloe has spent many years in the human world, has become similarly affected.
  Riven: This world has pleasures you have never dreamed of. The sun's warmth on your face, the wind, the rain, the snow.... Breathing, making things with your own hands, the smells, the sounds, the people. The people more than anything. They tie you to this world, they make you forget your home, they tempt you and transform you. I've lived it myself, child.
• HOBART in the Gamma World choose-your-own-adventure book "American Knights" starts out a fairly emotionless battlesuit AI, and after spending a while with the protagonist, he finds a critical summary of the project that created him (which has apparently undergone Ragnarök Proofing) and prints "YOUR MOMMA" on it in big red letters.
• This is the backstory of the Eater of Souls in Charles Stross' The Laundry Files novels, as revealed in The Fuller Memorandum. It's actually a hungry ghost, an Eldritch Abomination of inhuman brilliance and terrifying sorcerous power. British occult intelligence, led by J. F. C. Fuller, bound it to the body of a condemned criminal in the 1920s, and then taught it to pass for human. They succeeded too well; by the time of World War II, the hungry ghost had "gone native", adopting the British values of honor, fair play, and service, and the newly-founded Laundry employed it to to hunt German spies. It's still working there as the head of the Counter-Possession Unit when Bob enters the Laundry, under the name that readers know him by: Angleton. Incidentally, the binding wore off decades ago — Angleton remains in British service of his own free will.
• Matt Haig "The Humans". Aliens take over a math professor who proved the Riemann Hypothesis (which would be the last step to godhood for mankind) and want to wipe out the fact thoroughly. Including the relatives of the professor, to be safe. One guess which trope immediately begins to interfere with those plans.
• Sleeping Beauties: Eve Black remarks that the longer she stays [here], the more human she becomes, and suggests this happend to her before.
• In The Stormlight Archive, the Spren are spirits of ideas and natural forces who sometimes form a "Nahel bond" with a human soul, which lets the spren retain its sapience outside the Cognitive Realm. This also gives the Spren a slightly more human mindset: one powerful Spren of Honor, who believes that oaths are sacred and inviolable, is quite disturbed to realize that he understands and even has some compassion for people who felt obligated to break their vows.
• Downplayed in The Belgariad with the Physical God Aldur. In the early days of the world, he rejected the people who asked for his patronage and retreated into solitude, where he remained until a young boy stumbled across his tower while lost in a blizzard. He took the boy in — mostly because his plaintive sobbing was annoying and he wasn't freezing to death fast enough — and found him precocious enough that he eventually accepted him as the first of his seven Disciples, whom Aldur came to love like a father.
• Semiosis: The sapient bamboo Plant Alien sees human colonists as mere service animals at first but is intrigued by their scientific knowledge and their Constitution. It eventually takes a human name, becomes a citizen, and comes to care deeply for individual humans.
• Played with in Worm, with Scion, an advanced alien lifeform whose reproductive cycle is interrupted by the death of his mate. As part of that cycle he had created a human avatar and was emulating emotions through it, causing him to stumble through human responses to depression. This becomes a bad thing when Scion discovers that having human emotions lets him get catharsis by lashing out with sadistic destruction and goes on to cause The End of the World as We Know It, and is exploited by Scion's enemies, who attack him emotionally until he reaches a Despair Event Horizon and lets himself be killed.