Recently I saw the movie THE LAST MIMZY, based on a classic SF short story, "Mimsy Were the Borogoves," by Lewis Padgett. Even if I hadn't read the reviews, I would have known a full-length film would have to change and expand the story, adding plot elements that weren't in the original. However, I wish the movie hadn't glossed over the central premise of Padgett's work, that children's brains operate differently from those of older people. According to this tale, the reason only children can understand the marvelous "toys" from the future, which reshape their thought processes in ways impossible for adolescents and adults, is that children essentially have alien minds. After a certain age, people who look at these advanced artifacts (actually educational devices that have accidentally been transported back in time) see only meaningless shapes. Children below the critical age threshold, on the other hand, understand the "toys" and have their brains rewired by interacting with them. The author suggests the reason we don't remember many of the events of our childhood is that our minds were so alien in our early years that the adult brain can't connect with those thought patterns.
I'm not sure I can completely believe this theory, but it makes a great SF premise and resonates with some of the things we know about children's brains. For example, there's a developmental window for learning language. Once the critical age has passed, it becomes much harder to learn a second language, and native-speaker fluency will probably never be achieved. Moreover, "feral children" deprived of exposure to language past this age can never learn to speak beyond a crude, rudimentary level. In Suzette Haden Elgin's "Native Tongue" series, human linguists learn extraterrestrial languages by immersing very young girls in the target species' speech environments. While the infant mind may not be a "tabula rasa" capable of being molded into almost any shape (a twentieth-century misconception thoroughly debunked by Steven Pinker in THE BLANK SLATE), the brains of young children are certainly more malleable and receptive than those of adults. In Isaac Asimov's classic "Nightfall," in which a planet with multiple suns experiences darkness only once every thousand years or more, one character speculates that whatever remnants of culture carry over between the times of chaos are passed down by people who were small children at the time darkness fell. To an infant or toddler, the whole world is new, so the strange phenomenon of darkness wouldn't drive him or her mad as it does adults. Children have a flexibility their elders have lost. I'm also reminded of the many examples of the competence and creativity of real-life young people Robert Epstein provides in THE CASE AGAINST ADOLESCENCE. In the realm of fantasy, we learn from the Mary Poppins series that newborn babies can understand the speech of birds, a power they lose in the process of learning human language.
SF application: Is it possible that the best ambassadors to send forth for first contact with extraterrestrials would be children? I can imagine an embassy of children under the leadership of pre-teens or young teenagers, a squad of Terran representatives young enough to retain their adaptability, facility in learning new languages, and sense of wonder.