I performed an 80 hour sleep deprivation experiment in 1984 for a high school science class with 7 or 8 close friends. I can attest that the hallucinations are very real, typically between 2 and 4 AM, and that you lose the ability to hold conversations or even recite the alphabet (I still have the recordings). Endless hours were spent in conversations like "Did a hand just wave in front of my face?", "No, is there a monkey outside in that tree?"...