Behaviorism is dead in decision theory; the whole framework only makes conceptual sense if it is described in terms of beliefs and desires directly (as convincingly argued for by James Joyce). However, decision theory itself is dead as an appropriate model for all but a few applications. Getting such a theory to do any work for predicting human behavior largely fails despite the best efforts of researchers in multiple disciplines to add ad hoc constraints and behavior-fitting mechanisms to the theory's formulation. Instead of attempting to accommodate the various forces on human action as levers in the mental decision apparatus we are better off modeling behavior as resulting from the interaction of changing sets of adaptive rules with an uncertain and dynamic environment. The idea is simply to take the benefits that more general agent-based modeling has over traditional game theory and extend those analogously to traditional decision theory. The traditional version of decision theory may excel as a normative theory of decision making under known risk in stylized situations, but for more interesting and realistic problems we need a heuristic approach.

The world modeled by decision theoretic approaches is very far from the complex systems world. There are no interacting agents, no dynamic environments, no feedback, no contingent decisions, no growth, nothing but the simplest encapsulation of all that might be as states of the world and the actions and probabilistic events that bridge actions to states. Agents are nothing more than a preference relation over the states. Usually the preference relation is converted into a utility function in some way, but the conversion is part of the model, not the agent. Actually, there is a bulk of research that uses cardinal utility and that must be a feature of the agents. Despite being completely unsuited to complex systems, decision theory is worth investigating because it suffers from many of the same ills that game theory does and for which the heuristic agent-based approach makes an improvement. If insights from modeling complex systems improve modeling of non-complex systems then that is additional support for the superiority of agent-based modeling's heuristic approach.

As I have demonstrated elsewhere game theory is a simplified form of agent-based modeling: rule-following agents make actions contingent upon other agents' actions and the environment. There is just the one rule maximize utility and the burden of determining the utility function is pushed to utility theory (a modular part of the model that is also used by decision theory). Game theoretic models that replace utility theory with heuristics are exemplified by Axelrod, Grimm, Miller, Bednar & Page, etc. We can likewise replace the utility theory behavior driver in decision theoretic models. The motivation is that people, in fact, rarely perform the sort of calculations posited by decision theory and rarely have the information assumed by most of decision theory. People's behavior is generated by the interplay of many simple cognitive rules (Minsky, Dennett?) that are triggered by features of the environment. Modeling decision procedures in this way will produce higher-fidelity predictions and explanations.

The psychological support for humans' heuristic behavior is substantial and constantly growing (Dennett, Nowak, etc.). Of course, these are just psychological models and whether our conscious operation runs by adaptive rules or maximizing utility is irrelevant; the neuro-physical evidence increasingly lends support to the idea that what goes on in our mental theatre does not affect our behavior (Watson, etc.). That our behavior is more controlled automatically by physiological reactions, hormones, and the lower brain functions than the lofty operation of our frontal cortex means that even if the belief and desire model is better for modeling decisions, decisions do not affect behavior and hence will fail to make useful predictions. As Kant famously said, we cannot help but perceive our actions as being the result of the operation of our mind, but it turns out that this perception is illusory.

If the conscious mind doesn't affect behavior then there is no process by which the mind ought to make decisions. It can do whatever it wants so long as the body does the right thing. The evidence supports the claim that Joyce's non-necessary relation between decisions and actions is actually just correlation. So even if one creates an excellent model of decision-making one will not have really modeled anything except the cognitive wheels of the mind that never tough the world. In order to model what a person will do when confronted with a choice we should model the process with verisimilitude to how people choose actions with systems of rules. While this heuristic approach bares some similarity to behaviorism, it is only the realization that predicting decisions is pointless if that doesn't help predict behavior. What we want our model to match in the final analysis is behavior.