Kittens and socialization to prey...
In a pioneering set of experiments, Kuo (1930) raised kittens and rats together in the same cages. Kittens raised with rats never killed rats of the same strain when they grew up, although some would kill rats of a different appearance. The implication of Kuo's results was that kittens whose social companions during early life were rats formed social attachments to rats, inhibiting later predatory responses to them. However, when given the opportunity to form social attachments to other kittens as well as rats, other kittens were preferred. Kittens raised both with siblings and rats formed clear social attachments to their siblings. Nonetheless, these kittens did show a distinct tolerance of rats and a reduced predatory response towards them, although some eventually became rat-killers (Kuo, Z.Y., 'Further study on the behavior of the cat toward the rat', in Journal of Comparative Psychology, vol. 25, pp.1-8, 1938).