They mostly relate smells to many things. I notice they do learn real fast by sight also. My one example is when I place my BP in his feeding tank. The tank is always thoroughly cleaned after every feeding so he knows it only by sight. By the third time I put him in the tank, I can see he gets real alert when he gets put in there. He goes from chilled out and lazy to high alert. He knows what's up. It's real cool to see this reaction from a snake. So they do learn from sight in my opinion and retain the info for at least a week from my observations. So sight and routine triggers something with my bP....it triggers his feeding instinct. I also notice they do like to be handled by certain people....my sons BP...which I supervise because he's seven, seems to favor him.....he feeds him and handles him the most. I say this because the snake doesn't want to let go of him when my son tries to put him back in the cage.