My divided betta tank is in my bedroom also and I am not in there very often. When I wake up in the morning I feed them and then a few times throughout the day I go in and look at them and put my finger onto the glass and mess with them :P. They have each other to look at so I don't think they get too bored. Whenever i look at them they are ALWAYS doing something. Swimming along the glass, through plants, building bubble nests. I think they are happy as long as there is some sort of movement around them.
My other betta lives on the kitchen counter and goes nuts when people are near him. He swims all around his tank, especially on the side of the tank where the people are. And he opens up his fins, not flaring though, to show you how beautiful he is!
I personally think if you interact with them often, more of their personality comes out.