There have been many hypothetical experiments proposed on such topics as language, culture and isolated populations that would be at best impractical and at worst unethical to actually perform. Given the ability to fully simulate a human brain, however, along with a body and environment, would those experiments become viable? I imagine the computing power required would be staggering, and the setup work alone would probably be a lifetime's work. Where would you begin if you wanted to study the thought patterns of a whole village of people who natively speak constructed languages such as Klingon, Elvish or Lojban? There's always more than that influence in their lives, and every other influence is a variable.
But even if you could do it, would such experiments still be unethical? If you can simulate a whole human being, and you can copy her, branch her off into multiple timelines on a whim, merge her back together, move her between worlds at will and subject her to any kind of stimulus you so choose, whether pleasurable or painful, does she have the right to be treated with the same ethical restraint that applies to "real" humans? By the time we gain the technology to carry out these hypothetical experiments, we may prevent ourselves from doing so on the same ethical grounds that stopped us in the first place.
Mokalus of Borg
PS - Science fiction keeps revisiting this idea, and with good reason.
PPS - I had problems enough with my Creatures and Sims.