Yes. They do. Mine would go so far as to run headlong into the glass and knock himself out if there was a lot of fast movement that spooked him....either that, or he'd just suspend heads-up in the water, like he'd died of a swollen swim bladder or something...scared the p1$$ out of me the first couple times he did it....
Also, they get a little aggressive and territorial when they get big. Keep an eye out if he's in a community tank. He'll soon eat anything that will fit in his mouth....