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Some people can, some people can't. Sort of like those who can taste litmus? paper and those who cannot.
I see different personalities in all my snakes as well. Then again, I also spend lots of time in my snake room, observing each one when I can. My corns and bulls are the most curious.
The bulls/gophers will come right up to the front of their enclosures to see what the big noisy thing Emotion: it wasnt me is going to do next when I come in the room. The corns only get curious when I open their enclosures, otherwise, they just sit around and snooze. Occasionally, I'll get a chorus of hissing from my younger bull snakes (the gophers almost never hiss) but it stops when they realize I'm not a threat.
My boas and pythons sit in one spot and never move when I'm in the room. However, their eyes do.
My garters are jumpy, usually flinging themselves all over the aquariums I keep them in.
-cat