In real life, there are mental differences between types of animals that go beyond incompatible vocal abilities. If we managed to make an animal translator in real life, they would not be able to communicate and interact exactly like humans. Not so in fiction, in an otherwise realistic setting, the ability to talk to animals will often result in every species having the same mental capabilities as humans, which they apparently always did. You'd think they'd try harder to communicate with humans if this is the case, but they're content to wait until a human bridges the language gap for them.
Can lead to Fridge Horror, if all animals were sapient the whole time that means pretty much every human civilization in history has been constantly doing things that amount to slavery and genocide. The animals don't seem to mind though, their first reaction to talking to a human will never be begging them to spread the knowledge that animals are mentally equal to humans. They may even want their knowledge to be kept secret, despite this having no noticeable benefit to their species.
See also Amplified Animal Aptitude.
- The Legion of Super-Heroes had this in the Silver Age with the Legion of Super-Pets. Proty, a shapeshifting blob, was capable of not only turning into Superboy's shape, but speaking to the point where people could think he is Superboy. He could also communicate with all the other Super-Pets telepathically on a level implying that they were all similarly sentient. Including Superboy's dog.
- Marvel Star Wars: Plif has a small-scale one where the cuddly rabbitlike animals the Rebels have been playing with and allowing to sleep on their beds since arriving on Arbra reveal themselves to be sentient. After they do so they don't bother pretending not to be people around the Rebels and even sometimes act as diplomats.
- Harry Potter and the Methods of Rationality gives us this exchange between Harry and Draco, after Draco learns by accident of Harry's Parselmouth ability (which, as in canon, Harry himself was unaware of).
Harry stared at Draco.
"You mean just magical snakes, right?"
"N-no," said Draco. He was looking rather pale, and was still stammering, but had at least stopped the incoherent noises he'd been making earlier. "You're a Parselmouth, you can speak Parseltongue, it's the language of all snakes everywhere. You can understand any snake when it talks, and they can understand when you talk to them... Harry, you can't possibly believe you were Sorted into Ravenclaw! You're the Heir of Slytherin!"
"SNAKES ARE SENTIENT?"
- The Princess and the Frog demonstrates this trope when the two main characters are turned into frogs. Apparently there was even an alligator that learned to play the trumpet, but never thought of using his remarkable hand coordination to try writing down that he was sapient.
- The toys from Toy Story.
- Up plays this trope straight for the most part; the dogs that serve as the Big Bad's Mooks are extremely competent. However, Dug is an aversion similar to the Dexter's Lab example above, telling everyone he meets he loves them (being a talking version of a big friendly dog), while also being distracted by sounds that may be squirrels.
- Averted in Cloudy with a Chance of Meatballs. Flint develops an animal translator and places it on a monkey named Steve (voiced by Neil Patrick Harris). Steve is still depicted to have the intelligence of a monkey, being incapable of forming complete sentences and not being able to say more than his own name and whatever object is in front of him at the time.
- Pound Puppies and the Legend of Big Paw takes place in a world where dogs and humans gained the ability to communicate in the middle ages, and it seems to be common knowledge among humans. This gets a little disturbing when you realize that despite full knowledge that dogs are as intelligent as humans, they are still treated as pets.
- Variation with TRON where instead of animals, it's computer programs. If you get digitized into a computer you can have a normal conversation with a word processor.
- The Doctor Dolittle series revolves around the title character learning to speak the languages of the animals. All animals in the series are intelligent, and have languages (even, for instance, shellfish, whose languages he spends much of the second book specialising in).
- Averted in Children of the Red King. One of the characters can talk to animals, who generally have less of an understanding of the world than the humans.
- Toyed with in The Immortals. Animals have unique magic that lets them "talk" to each other, and intelligibly. Daine communicates with them easily and few of them are too simpleminded to grasp her ideas. However, they don't think to try interspecies communication until Daine suggests it, because they're not good at "ideas" and other kinds of abstract thought.
- Junior/Hook in Dinoverse might not be at the same level as some of these, but when he has to rely on Will to survive he carefully conceals not just that he's healing well but also all the things he's been learning. Which include wound-binding, fire starting, and deciphering symbols scratched on walls.
- In one of the Land of Oz books, the characters wonder why Toto is the only animal in Oz who never talks. He reveals he could talk, but was afraid if he did, Dorothy would stop treating him like a pet. And he kinda liked the pampering.
- In the Known Space series, dolphins turn out to have been sapient all along, and are granted the same rights as humans in the 1990s. Humans develop a thriving industry in selling artificial hands to dolphins, and they sue us for whaling.
- The Wild Thornberrys may be the most thorough example in terms of demonstrating that every single animal is actually sapient, each episode has a new location and group of species demonstrating this to Eliza. Environmental protection is always promoted, but not recognizing animals for the sapient beings they are.
- The PBS show Arthur eventually revealed that babies and animals are able to communicate, and both secretly sapient. Even insects were eventually shown to be sapient.
- Subverted in Dexter's Laboratory, where Dexter creates a device which allows a dog to talk, only for the dog to just repeat things like, "Look, there's the thing! It's a thing! Look! A thing! There it is!" Further demolished when the dog's owner shows up, and is just about as smart as the dog.
- Usually averted in Dungeons & Dragons. Most spells or other magic used to communicate with animals state that the animals' speech should be limited by their lesser intelligence, so you aren't going to be able to have a philosophical discussion with a dog.
- In Back at the Barnyard, it's mentioned that the reason that the reason why the main characters don't let humans know they can talk is because they wouldn't be able to live on the farm anymore. Evidently, they suffer Happiness in Slavery.