I believe that we all like to think we would behave nobly and rationally when confronted with an alien life form. You might think that it would be easier to relate to a sentient creature that looked at least somewhat familiar, something that had recognizable traits: ears, eyes, nose, mouth. I sometimes wonder and fear what my reactions would be to meeting a new race of sentient beings, or even finding out that a current species on Earth is sentient.
I like to pretend that no matter how strange and grotesque (or eerily familiar) they might be, that I would judge them based on their culture, their rationality, and the context to which those traits apply. Until I'm confronted with this situation, I just don't know how I'll react. I'm not sure I would be as calm as Ulysse Merou in Boulle's novel, I might very well lose my mind like Professor Antelle rather than cope with the shock. I would particularly begin to question my humanity and its value if confronted with a race of human-like inferior beings.
In fact, I'm not sure which would be worse. I think I'd almost rather meet a race of intelligent apes than a race of animal-like humans. With human-like beings I would still have the need to communicate with them, but not the capability, at least not on the level that I'm used to communicating with...most...human beings. While my physicality with a dissimilar species may be somewhat limited (depending on how put off I would be by their appearance/cultural barriers), I think I'd rather live without sex and creating a family than without companionship.
Of course Merou was faced with both of these and I found myself fascinated by his ability to relate to both alien groups in different ways. He allowed himself to be physical with the human-like creatures, although he felt a great deal of guilt and embarrassment about it, but he also had a deep friendship with some of the sentient Apes. I think the fact that he was able to have both was probably what kept him sane, along with his attempts to spark intelligence in the human creatures.
Sometimes I wonder why literature isn't studied in psychology classes, at least for the sake of discussion. I would have been fascinated by a Psychology of Literature class in college. Hell, I'd even take one now if I could afford it and knew of someone who was teaching it. These are means of presenting situations and experiments that can never conscientiously be carried in real life, assuming they are even possible to begin with. But it will lead to a deeper understanding of the human psyche, at the very least of the author who wrote the work. I think Boulle presents us with the very best and the very worst of human intellect; it speaks highly of someone who is willing to expose both to his readers.