- In The Evil Wizard Smallbone, whenever someone is shapeshifted into an animal, they become that animal in mind and body unless they've been trained on how to keep their mind intact. This is how the villain keeps his minions in line.
- Animorphs uses this a lot:
- Every animal morph comes with its own set of animal instincts. The first time any given character morphs a new animal, they're at least momentarily swept up in its mindset and often start running for cover or looking for food etc until they recall themselves or are stopped by the others. Ant and termite morphs have instinctual responses so strong that instead of the usual narration ("Too bright! I ran under the couch" etc) first person pronouns are dropped entirely, and unlike with those other morphs the Animorphs are utterly horrified once their own personalities reassert.
- They can also lean into these instincts intentionally to act like the animals they morph and use their skills, like flight.
- Human morphs, though they're rarely used, also come with some of the inherent personality of whoever has been morphed. Cassie in Rachel morph finds herself having to restrain impulses she recognizes as foolish. Tobias morphing Taylor, on the other hand, finds that while the Taylor he knows is manipulative and cruel, her inherent personality is gentle, a little afraid, and inclined to joy.
- Centipede-like Taxxons are completely consumed by Horror Hunger, causing them to instantly consume anything even remotely edible around them (including their injured comrades). Yeerks with Taxxon host bodies cannot stop the feeding once it starts and can barely make the host body focus on anything besides feeding; morphing into a Taxxon causes similar issues. The hunger is so bad that a group of dissident Taxxons agree to help the Animorphs in exchange for being allowed to morph into some less-ravenous forms and stay in those forms for more than two hours.
- In The Belgariad, Belgarath points out that transforming into an eagle wouldn't necessarily help you travel faster, because you were likely to get sidetracked by every tasty animal below, observing that while they look magnificent, eagles are really very stupid birds. More generally, this is a hazard of shapeshifting, with Belgarath dedicating an extended passage in his self-narrated prequel to explaining the insidious effect that taking animal form can have, since the change is absolute - an extended period as a wolf, for instance, leaves him interested in the idea of a wolfish life and taking up with a young female wolf who's taken an interest in him, daydreaming of the hunt, companionship of a mate, cubs, etcetera. Interestingly, the reverse also applies, as his wife, Poledra, was originally a wolf (in fact, she was the young female wolf mentioned above), and after giving up on the idea of him mating with her as a wolf, changed into a form he'd find more attractive - a woman. The narration makes very explicit that she is now a woman - one who used to be a wolf, and could transform back whenever she wished (among many other things), but still a woman.
- Jack Chalker, as can be expected by the prevalence of transformation plots in his writing, makes frequent use of this.
- Downtiming The Night Side: Used specifically to avert Different for Girls. Also applied to most of the transformations that are a core theme of much of his work, particularly in the Well World series and even one-offs like Web of the Chozen.
- Especially nasty in the Soul Rider series, where the revolutionary state of New Eden imposes this on its female population by a binding spell. A transformed "Fluxgirl" is literally ruled by her body, which now craves constant sex, has difficulty with concentration on long-term projects, and cannot read, write, calculate, or figure out complicated machinery.
- Chalker also specifically inverts this trope in The Identity Matrix, where the body can be made the plaything of the mind by making mental adjustments that influence the endocrine system, affecting things like muscle development and fat distribution.
- A curious variant in Charlie and the Great Glass Elevator: When Grandma Georgina (who is in her late 70s) is aged to 300+ years old via a Rapid Aging formula, her memories change to reflect the times she would have been born in and lived through had she come to this point naturally. (Her earliest memory is arriving in America on the Mayflower.) When she is returned to her natural age, these memories apparently disappear.
- In H. P. Lovecraft's Cthulhu Mythos stories, the outer god Nyarlathotep is said to have a thousand forms. Each form is essentially a separate entity (it's implied that he can even manifest several in forms at once). As such, the behaviour and personality of different forms can be completely different. This is only vaguely implied in the original works, but considering that Nyarlathotep's different forms functions essentially identically to the Avatars of Hindu mythology, this is indeed probably the case, although a central intelligence connects them all in some sense.
- In Oath of Gold, the third volume of Elizabeth Moon's The Deed of Paksenarrion, the Kuakgan talks about this with Paks, who was unable to continue her life as a paladin-in-training after being captured, tormented, and rescued, and who is at the brink of suicide when he finds her leaving her worldly goods in his grove's offering-bowl. She also hasn't eaten properly for quite a while, and has a lot of half-healed wounds. The analogy he draws between the mind and the body is that of the snail and the snail-shell; if you poke holes in the snail-shell, will the snail live?
- Terry Pratchett's Discworld series plays it relatively straight. One notable example, and a reference back to it in a later book, likens the mind to water and the body to a jug or vase. The water is only water, it does not become the container, but it does take on the container's shape.
- The longer Discworld werewolves spend in wolf form, the more they start to think like a wolf. The reverse is also true: They become more human the longer they spend in human form. They never entirely become one or the other, this is the true "curse of the werewolves".
- The same is true of Borrowing: The longer you inhabit something else's brain, the more you start thinking like that something else. In Equal Rites, Esk nearly starves to death because she loses track of her human self, but doesn't have the proper instincts to feed herself as a falcon.
- Later in the book there's the bit where Granny Weatherwax Borrows the Unseen University, and thinks like a building upon coming out of it.
- The Great God Om points out in Small Gods that the shape of the body influences the shape of the mind, so if you spend too long in the body of, say, a tortoise, you begin to think like a tortoise.
- It is also true on the Disc that the body is sometimes a plaything of the mind. In Witches Abroad, a cat is transformed into a human just by making him really believe that he's human.
- A major theme of Thiefof Time
- When the Auditors create human bodies for themselves, they eventually start feeling emotions. The end result is a mix of Auditor and human that has serious trouble being either.
- The point of the "water in a jug" analogy is Myria LeJean's realization that it is wrong; for a mind in a body, the "water" is truly changed by the jug.
- The History Monks have a Dalai Lama-type figure whose wisdom reincarnates throughout the ages and is present from birth. As his current incarnation is a baby, however, his sage wisdom often loses out to sentiments like "wanna bikkit".
- Addressed in a more technical form in The Science of Discworld, in which the complicit relationship between physical brain processes, external experience, and minds are discussed.
- Dogsbody has the sentient star Sirius put into the body of a newborn puppy on Earth. In an inverse of most examples here, at the start he has almost no memory of his old self or old life and is functionally a normal puppy, albeit one with weird eyes. As he grows and becomes more physically and mentally capable he becomes aware of a large, complicated green space inside of him, and then of what he truly is and why he's on Earth, but for much of the book that's a delicate, difficult example. Another star tells him it will be easier when his body has grown up - still, his hyperintelligent star thoughts are muddied by simpler dog thoughts, and when he runs away those dog thoughts strike when his favorite person is about to come home - it's unthinkable to not be there to greet her.
- In a Dragonlance short story, an If I Can't Have You… plot winds up with most of the cast shapeshifted. If they do not wear something belonging to their human (or otherwise) selves, the human mind will eventually succumb to the animal form. Taz comes very close to being permanently stuck as a squirrel.
- The Dresden Files:
- One of the laws of magic is to never change someone's form against their will: it will eventually destroy their mind, leaving just a normal animal. Changing your own form is allowed — partly because it's consensual by definition, partly because people who transform themselves instinctively protect their minds to avert this trope — but still carries risks.
- A good example of a first-person viewpoint to this trope is Harry's transformation into a hexenwulf in Fool Moon, and subsequent gradual loss of control to the monstrous wolf's beastly instincts. Hearing it from his narration is pretty freaky, and when he turns back, he's sickened and horrified.
- At one point in Changes, the main characters are transformed into a pack of hounds as part of a plan to sneak into the stronghold of the Red Court vampires. Despite everyone involved being willing to undergo the change, the transformed characters slowly start thinking more and more like dogs, gradually forgetting the urgency to turn back into humans once they get where they need to go.
- In Skin Game, the shapeshifter Goodman Grey transforms into a different man, but immediately starts exhibiting the man's nervousness and fear at the situation he was in before he died.
- Dr. Franklin's Island has a pair of teenagers transformed into a birdlike monster "human enough to horrify" and something like a small manta ray, respectively. Before, they would have considered their minds changing to be the worst thing on a great pile of terrible things, but after, Semi reflects that it's a help. As a fish, she doesn't get bored and is perfectly content to swim and daydream, and Miranda finds great joy in being able to fly. More of a problem is when instead of coexisting with their human priorities and thoughts they replace them.
- In Earthsea stories by Ursula K. Le Guin, shapeshifting works this way: the longer a wizard stays in a given form, the more his mind is taken over by that form's instincts, and the more he risks forgetting he was ever a man. Legends say many mages turned themselves permanently into dolphins this way, and one tragic fable concerns a wizard who so enjoyed turning himself into a bear that he ultimately became the bear and killed his own son.
- In A Wizard of Earthsea this happens to protagonist Ged. He almost loses his mind when he is forced to flee over a long distance as a hawk. By the time he escapes, Ged is so far gone he does not remember magic, so he cannot change himself back. Instead he flies — probably by animal instinct — to a familiar place: the house of Ogion, The Mentor. Because Ogion is a powerful wizard who knows Ged's True Name, he can restore his former student's body to human form. However, it takes time for Ged to recover psychologically: weeks pass before he can even speak.
- This trope is a recurring element in Fablehaven. When you transform (with the exception of the Eternals' guardians) you become yourself if you had been born a member of that species. It's most used with magical creatures that have human avatars, but it was a major plot point in the first book when Grandma had to fight her chicken instincts to get a message through.
- In Robin Jarvis' Hagwood trilogy, the insect monster known as Frighty Aggie was once a werling named Agnilla Hellekin. She was so skilled that she could wergle (that is, transform) into any forest creature. However, she wanted a bigger challenge, so decided to try wergling into an insect. This had never been attempted by anyone before and was regarded as highly dangerous. Still, she successfully managed to do so three times, but each time her mind was being irreparably damaged. On the third try, she could not wergle back to her original form and permanently became a grotesque insect monster with no memory of who she had been before. Her story became a cautionary tale to all werlings to never try wergling into shapes that were forbidden to them.
- This trope plays both ways in Harry Potter: If a person is involuntarily transfigured into an animal (and this includes werewolves), then they lose their human mind for the duration of the spell. However, with years of study, and at great risk, a wizard can train him/her self to transform into an animal at will and retain their human mind — mostly. (Wormtail suffered no ill effects from being a rat for twelve years straight, but Sirius sometimes turned into a dog to ameliorate the stress caused by Dementors.)
- Sirius also once says that James had always joked he had a much sweeter disposition as a dog, implying that there are at least mild changes in personality/attitude which reflect the behavioral patterns of the animal they transform into. Of course this aspect is debatable because of the fact that the wizard doesn't choose which animal they transform into, they find out only once they've completed the training and see what they become (much like the Patronus charm), and implies that the animagus form reveals, in part, the true nature of the character in question. Even so, it is easy to see that a character like Sirius may have very playful and loyal dog-like nature, but frequently behave in harsh or unforgiving ways due to the emotional and psychological trauma of his human life, which might be less at the forefront of his mind because of the less linear nature of the dog's mind. It is also the way he escaped Azkaban without notice — the Dementors could not detect the less complex dog mind, and therefore didn't realize a human was leaving the prison.
- Likewise, a Horcrux is Nigh-Invulnerable because it's the inverse of a mortal—the spirit it contains will instantly die if it's destroyed, but the physical self regenerates.
- The author also noted that animagi tend to suffer a sharp decrease in IQ when in animal form, presumably due to the shrinkage in brain size.
- In Heralds of Valdemar many mages are capable of taking animal shape, but rarely do as even brief periods in other shapes are detrimental. One Tarma and Kethry story features a mage who's been spending far too long in bear form and losing her grip on reality. Kethry explains why this is a problem.
Kethry: "When you shapechange, you become the thing you've changed to. You're subject to its instincts, its limitations. Including the fact that there's not enough room in a beast's head for a human mind. That usually doesn't matter much. Not so long as you don't spend more than an hour or two as a beast. You don't lose much of your humanity, and you probably get it back when you revert. But it's not guaranteed that you will, and the stronger the animal's instincts, the more of yourself you'll lose."
- Winds of Change has Dawnfire doing an Animal Eye Spy when her human body is killed, leaving her soul anchored to a hawk. This is a magic, smart hawk but she knows she has only so much time before her memories and sense of self degrade, leaving her as, well, a smart hawk that responds to her name. Another character who knows something about "transfer spells" proposes moving her to a body with a large enough brain that she can stay herself, or to "something like a sword".
- Every Uplifted Animal and animal-shaped angel in the setting is noted as having a large head and a broad forehead, signifying a big brain that can support a human-level mind.
- The Host (2008): The Souls are strongly affected by natural instincts and sometimes memories of their hosts. If a human host loved someone before the transformation and this feeling was mutual, its very likely their souls will become a couple. It happens even if souls haven't met each other before.
- Industrial Society and Its Future: Discussed by Kaczynski as due to desires, feeling etc being things which can be physically affected this opens up an ability to manipulate our behavior using drugs or other means. He fears too this will only increase into total control.
- Journey to Chaos: When Eric mana mutates into a grendel, his personality and worldview permanently change. Even after his sanity is restored, he thinks like a monster. He still has his human memories but they are interpreted by his new monster mindset. He soon realizes that the mindset for monsters and mercenaries, and monsters and mages are striking similar and so there is little true change in his core personality.
- "Lady Into Fox" is about a refined elegant woman, and her husband who was a fox hunter. One day she—with no explanation—turns into a talking fox. They try to live their lives as best as they can, but she gradually starts to lose her mind. She becomes more interested in chasing rabbits; soon enough she slowly loses her humanity, forgetting who her husband is and losing her ability to talk. The once well-mannered dainty lady is now eating live rabbits in the living room, with blood everywhere. It was never explained why she transformed but it's implied God or some karmic force punished her husband for killing foxes for a living.
- In an interview
, the author of The Locked Tomb said that in this setting, 'mind' loses to 'matter' nine times out of ten. Gideon’s mind is constantly in danger of being sucked away into the storm drain of Harrow’s matter. Revenants are minds that have temporarily anchored themselves to foreign matter, but over time the matter exerts itself, and the mind starts to fall apart. So when you get a mind that’s big enough not only to resist the matter it’s attached to but actually to start burning that matter up… well, what kind of mind could possibly be so powerful??
- The Magicians: Taking on the form of an animal results in the shapeshifter often being at least partly overtaken by their instincts, a fact that the Brakebills facult openly exploit: in order to send the students to Brakebills' southern campus in the Fourth Year, they transform them into geese, entrusting that their instinctive ability to navigate will allow them to travel to Antarctica. Later, as part of their Training from Hell, they're deliberately humiliated in a lesson in which they must transform themselves into arctic foxes — and then experience the logical consequences of combining animal instincts and several months without sex.
- Max & the Midknights: The Tower of Time: At one point in the book, Millie accidentally turns Kavyn into a cat. In his new form, Kevyn finds he has a newfound craving for tuna and a belly rub, and can't seem to stop licking himself. He's also seen partaking in stereotypical cat behaviour like napping.
- Mithgar: A shapeshifter in their animal form is said to have the mind of that animal, albeit one that will occasionally have thoughts similar to those of a human. The flip side of this is that a shapeshifter in human form will occasionally have thoughts similar to those of the animal they transform into.
- Old Kingdom: Lirael can make skins that allow her to take on the form of an otter, or a bear, or an owl, but each one alters her temperament for a while, even when she takes them off (the otter-skin gives her a great craving for fish, for example).
- The Prefect: One glitter belt polity consists of disembodied minds interacting entirely virtually, but recognizing that The Mind Is a Plaything of the Body, they maintain their human experience by becoming not brains in jars but instead brains-and-endocrine-systems in jars.
- Realm of the Elderlings: In the Farseer Trilogy, Fitz fakes his death by abandoning his body and binding his mind to Nighteyes's. When he is brought back into his body it takes him half a year to remember how to be human, and even then he is much more wolfish than before.
- Ren of Atikala: Amulets exist that can allow the wearer to assume the form of another species, but the change has an effect on the mind of the wearer. For example, a kobold who wears an amulet of human-shape may no longer be able to understand Draconic and will have a harder time telling individual kobolds apart, but is more easily able to tell humans apart than they were before.
- Seraphina: In this fantasy world, dragons can shape-shift into human forms called "saarantrai" ("saarantras" in the singular). While in saarantras form they still retain their near-eidetic memories, pedantry, and innate logical processing, they can be affected by intense human emotions, which they lack in their natural reptilian form. For this reason, they rely on Emotion Suppression a la Vulcans while shape-shifted.
- Seven Years Awesome Luck: Trick has picked up many cat traits from his seven years, from rubbing his head against friends, to chasing laser pointers, to hunting mice. He's possibly especially susceptible since he likes being a cat.
- In The Ship Who... Sang, a mission to trade Corviki technological secrets for performance of Shakespeare is complicated by the aliens' planet having a methane-ammonia atmosphere. Not satisfied by watching transmissions, Corviki provide the visiting humans with Remote Body technology, allowing them to pass out and inhabit Corviki 'envelopes'. Actually seeing and talking to the aliens makes it immediately clear that they've got Bizarre Alien Psychology and regard everything in terms of color and energy - they still get a lot out of the play, but not really what humans would get. Both in their 'envelopes' and in their human bodies in orbit, the actors all find themselves affected and starting to think in Corviki terms, much to the chagrin of some; only the most self-absorbed of the actors can resist this very well. Three of the actors choose to Stay with the Aliens and abandon their human bodies, and another is forced into it. Part of the And the Adventure Continues of the first book is an assignment to return to Corviki to clarify a point about the technology, and to find out if those actors retain their memories and individuality at all.
- Skulduggery Pleasant:
- This is played more subtly with sorcerers as a whole, who are often extremely Long-Lived and if they use magic regularly, age incredibly slowly, living for up to two thousand years. It's not portrayed as the most positive trait, as at best, this results in Immortal Immaturity for reasons heavily implied to be related to brain chemistry and structures (as one character puts it, "young bodies have young minds" - and is indicated to be right based on the personality shift of one character who undergoes a case of rapid ageing from eternal 30 year old to 70-something). Well, that and the knowledge that they're going to live for centuries and can afford to muck about. It's also suggested that some of the centuries old sorcerers, even the good ones, lose a bit of their humanity along the way.
- Werewolves, as usual, though they're actually extinct by the time of the series precisely because of this with the werewolves themselves having been horrified by their transformations into ferocious monsters and worked to prevent it being passed on. It only becomes significant because the genetic potential remains and is awakened in at least one person as part of one of the Big Bads experimenting by giving ordinary people magic.
- Skulduggery himself is an interesting example, since he's a living skeleton and has a consciousness rather than a brain. As a result, he doesn't eat, smell, or taste, and his sight works in different ways (for instance, he has no eyes, so he can see in the dark). This doesn't make him emotionless, far from it, but it does mean he's a little more detached and logical. It also means that when forced to resort to possessing someone, he along with Cadaver, for that matter is a Sense Freak, utterly fascinated by sensations that he hasn't felt for the last 300 years. Also, he hasn't had a libido for three centuries and spontaneously tells several people - including the very confused alternate counterpart of his Archenemy - that they are very attractive. Valkyrie thinks, somewhat amused, that it must be like waking up as a Hormone-Addled Teenager.
- A Song of Ice and Fire: The skinchangers (who do not physically transform but can telepathically possess certain animals) have trouble remembering their human selves. When Bran Stark is being taught to control his power, he is told to do certain things as a wolf to help keep his mind in control. He keeps forgetting to do these things, and as a result he acts largely on instinct while in wolf form. Some of the older, more experienced skinchangers seem to be able to use their human intelligence more effectively, however, though it is mentioned that certain forms increase the risk of losing touch with humanity. When a skinchanger's human body dies, they can possess their animals to keep on living, but eventually the animal forgets its human life and becomes an ordinary beast.
- The Stormlight Archive: Parshendi have the ability to change forms suited for specific roles, and they shift slightly in temperament depending on form. Dullform are extremely stupid, mateform are playful and sexual, workform are non-confrontational to a fault, and stormform is flat-out Demonic Possession. Nimbleform and warform have minimal mental changes, but warforms still enjoy obeying orders from their lawful superiors.
The Stranger Times: A man is made into a
dog-like beast called a Were. Initially, he is simply given super-senses and the ability to change shape, but the Beast inside him slowly warps his mind to become wrathful and animalistic. Not that this guy was particularly nice to begin with.
- Strata: Marco was bought up on Earth among humans and even has papers to prove he's legally human. He still possesses the Kung instinct to fall upon anything that threatens or surprises him, and destroy it utterly.
- Tales of the Five Hundred Kingdoms: We're told that only the most powerful Sorcerers or Sorceresses can transform a person into an animal without that person losing his mind to the animal. However, since the books focus on Godmothers, we don't see this in action.
- In The Fairy Godmother, Elena transforms Alexander into a donkey, but has to give him regular time as a human.
- In The Snow Queen, Aleksia takes several animal forms, but even as a polar bear (which has a large enough brain to "fit" a human mind into) the animal instincts get stronger the longer she remains changed.
- Three Men in a Boat: There's a several pages long passage detailing how a person's mood depends entirely on what they are eating, and what this food is doing to the body.
- Tortall Universe: In The Immortals, Daine finds that thanks to mind-speaking with and turning into animals, that she can no longer eat wild game. For a while she can still eat beef, pork, chicken, and fish because she's never had an interest in inhabiting the minds or taking on the shapes of barnyard animals or fish, but by The Realms of the Gods she can't even do that.
- Wild Cards: Jeremiah Strauss is a shapechanger who turned himself into King Kong and then spent several years acting like a gorilla and trying to carry blonde women to the top of the Empire State Building. Later transformations into a werewolf from The Howling and the Creature from the Black Lagoon almost turned out badly as well.
- Wren To The Rescue: The protagonist is turned into a dog, and is explicitly warned that the longer she spends in that form, the more difficulty she will have retaining her human mind; she gets out of it with no more than a few transitory dog habits. In the sequel, her friend Tyron is forced to spend a significantly longer time as a dog and only retains his identity by extreme effort.
- Xanadu (Storyverse): Many individuals develop compulsive tics, habits and instincts to match their new bodies. In "Against Type", Nicodemus, who is transformed into a giant rat, gains the innate twitchiness and nervous disposition of a prey animal, strongly prefers to arrange his bedcovers into a nest in which he can completely hide himself, and develops a compulsive habit of stealing and hoarding small shiny objects.
Nico cringed a little as his friend and co-worker lifted it into the back of the Honda. "It's mostly just junk. Useful junk, I hope. But junk. I... I can't help it. I've been able to fight off a lot of ratty behaviors, but I need an outlet, so... um. Guess I'm a packrat."
- Xanth: In the very first book, Magician Trent can change anyone into any animal. The form comes with instincts built in. Trent said something like (paraphrasing): "If you're a turtle, unless you have the instincts of a turtle, you couldn't survive as a turtle." Later books introduced a character who could shape-shift but didn't get the instincts, making it a much more limited talent. This was due to her demonic heritage; it wasn't even her personal magic.
