Impression (Dragonriders of Pern)
Impression is a practice in the Dragonriders of Pern novels by Anne McCaffrey involving a human forming a mental bond with one of three creatures native to the planet Pern, on which the stories are all based. The three animals are, in the order of their coming into existence: Firelizards, Dragons, and Whers.
Firelizards are the only of the three that are a native species. In the series, humans have begun to colonize the stars, and a group sets off for Pern with (to their later grief) little information about the planet in question. Shortly after arrival, they encounter small, winged creatures of some intelligence, roughly the size of a crow or smaller.
The first Impression is accidental. In the course of their discovery of the creatures, newly hatched young are found and fed. The young, in a manner similar to many avian species on Earth, 'imprint' on the humans, and remain with them. The fact that the imprint is more than just a superficial imprint is discovered shortly thereafter. The connection is largely empathic in nature, and serves a purpose as a communication tool vital to the survival of the creatures in their native habitat, which is regularly under threat from a highly inimical foreign 'lifeform' that necessitates a coordinated, aggressive defense. In the wild, the bond attaches the creature to its native flock, allowing for instantaneous communication in times of danger, from any distance. With a human bond-mate, it allows the firelizard to communicate emotions and visual data, and affects both the firelizard and the humans' emotions at a very basic level, in that when mating time comes around, human bondmates respond to the emotions generated by their firelizards, and firelizards echo their humans' emotional states, becoming agitated or angry when they do, and calming by the same method. Firelizards will Impress to anyone, of any age.
Upon the discovery of the inimical foreign 'lifeform', Man did what Man does best, and adapted an existing animal to serve a necessary function in the aid of human survival, though they used methods far beyond current technology to do so. Dragons, as they were named, for their resemblance to the creatures that exist in human lore, Impressed, but the function of the bond was altered. The dragons possessed greater intelligence, which mutated the bond from solely empathic/visual to a true telepathic/empathic bond. For the dragon, the bond is wholly necessary for the continuation of life, a genetically-programmed necessity, put there to prevent a proliferation of large, carnivorous, flying, fire-breathing creatures that were not under direct human control. The only exception to that rule is a breeding female with eggs she needs to guard. In such a case, deprived of her rider, the breeding female will remain long enough to ensure her young hatch, then die. They are, in effect, a symbiotic lifeform, requiring attachment to another lifeform to live, but providing benefits in exchange. The bond allows for instantaneous communication, and since the dragons are still animals, allows the human in the equation to exert control over animal instinct, to a certain degree. Again, the bond works both ways, with the rider deeply affected by their dragons' amours. For the human, the bond is not quite as all-consuming as it is for the dragon, but severance of the connection results in either death by suicide, insanity, or a lifetime of pain and grief at the loss of a creature that has, in essence, become a part of ones self. As dragons served a vital, necessary function for the continuation of the existence of humankind, their Impression choices were controlled by some means. The largest, golds (the primary progenitors of the next generation) were tweaked so they would only Impress females. The next three largest examples of the species, bronzes, browns, and blues, were tweaked so they would only Impress to men. Greens could Impress either sex, though after a while, females ceased to be allowed to attempt Impression, as the feudal society in which they lived felt they served a better purpose birthing the next generation, and greens became solely male-ridden for a very long period.
Whers were created when an attempt to make a second batch of dragons was undertaken unsuccessfully. They are the most problematic of the three species, in that they are inconsistently portrayed in the books. Indeed, in the first book written, though whers are introduced, there is no indication that they Impress at all, nor that they possess a dragon-level intelligence, though there is mention made of them being utterly loyal to those 'of the blood', referring to anyone descended from a particular individual, though how this is arranged is never specified. In later books, it is indicated that whers do indeed Impress, but that the bond is more akin to that that firelizards utilize, that is, it is telepathic, but neither wher nor human suffers unduly if the bond is severed. Like with firelizards, the bond is not sex-enforced.