The original ghosts had specifically written patterns: Blinky chases pac man where he is. Pinky targets 4 spaces in front of you. Inky targets based on Blinky and Pac's positions. Clyde sticks to a corner until you get too close.

They only reverse on their own when the mode changes or you get a power pellet, otherwise they have to wait until a corner, otherwise you end up with behavior like you see in this where you both quickly dance back and forth on the otherside of a wall