Behaviors are constructed in a bottom-up fashion: First, the processes that should react quickly to fast changing stimuli are designed. Their critical parameters, e.g. a mode parameter or a target position, are determined. When the fast primitive behaviors work reliably with constant parameters, the next level can be added to the system. For this higher level more complex behaviors can now be designed that influence the environment, either Directly, by moving slow actuators, or indirectly, by changing the critical parameters of the control loops in the lower level.
After the addition of several layers, fairly complex behaviors can be designed that make decisions using abstract sensors based on a long history and that use powerful actuators to influence the environment.
In a soccer playing robot, basic skills, like movement to a position and ball handling, reside on lower levels, tactic behaviors are situated on intermediate layers, while the game strategy is determined at the topmost level of the hierarchy.