Well, for one dietary necessities and poisonous substances can give a good clue of their evolutionary diet- especially if you weigh it against what they have on their planet. That and whether they were prey or predators. Isolated or moved in packs or herds.

You know you can just say you. I already said that I wouldn't go wavin' it around. [He makes an idle gesture.] Separating yourself from it isn't gonna do you much good. The problem with trauma in any species is that when you go through an experience you desperately want to survive. Someone more aware knows how to turn that off when they have survived and the immediate threat has been neutralyzed. But those that suffer afterwards don't know how to turn it off, a part of their brain is always in survival mode.

You're not turning it off. You're just shovin' it off to the side.