Abstract: Methods and apparatus for modeling behavior. A computer model includes an agent having one or more beliefs, a world model, and facts. Behavior is modeled by frames including workframes modeling a time-consuming portions of an activity or thoughtframes modeling non-time-consuming portions of an activity or information processing. Detectables model acquisition of, and response to, information during a defined portion of an activity. A detectable tests facts to form beliefs of the agent, which can affect continued performance of the activity. The model is run by selecting for each time one of the frames to be the working frame; maintaining a context of active frames representing activities that are underway at any time; performing the working frame until it completes or another frame is selected to be performed in its place.