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This book describes an agent-based model dubbed Agent_Zero, which was constructed using a significant volume of contemporary cognitive neuroscience. Agent_Zero is a new theoretical entity that exhibits observable behaviors generated by the interaction of affective, cognitive, and social components. Its affective component is based on the Rescorla–Wagner model of conditioning and extinction, while its cognitive (deliberative) component reflects biases and heuristics in probability estimation. The book presents Agent_Zero as a new, neurocognitively grounded, foundation for generative social science, a simple explicit model of individual behavior in groups that includes some representation of “the passions,” of (imperfect) reason, and of social influence. This introduction explains the motivations for constructing Agent_Zero, its components, and its basic mathematical scaffolding. It also provides an overview of the book's organization.

This part of the book describes explicit mathematical models for the affective, cognitive, and social components of Agent_Zero. It first considers some underlying neuroscience of fear and the role of the amygdala before turning to Rescorla–Wagner equations of conditioning. In particular, it explains how the fear circuit can be activated and how fear conditioning can occur unconsciously. It then reviews some standard nomenclature adopted by Ivan Pavlov in his study, Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex, with emphasis on David Hume's “association of ideas,” the theory of conditioning, and the Rescorla–Wagner model. After examining “the passions,” the discussion focuses on reason, Agent_Zero's cognitive component, and the model's social component. The central case is that the agent initiates the group's behavior despite starting with the lowest disposition, with no initial emotional inclination, no evidence, the same threshold as all others, and no orders from above.

This part describes the agent-based and computational model for Agent_Zero and demonstrates its capacity for generative minimalism. It first explains the replicability of the model before offering an interpretation of the model by imagining a guerilla war like Vietnam, Afghanistan, or Iraq, where events transpire on a 2-D population of contiguous yellow patches. Each patch is occupied by a single stationary indigenous agent, which has two possible states: inactive and active. The discussion then turns to Agent_Zero's affective component and an elementary type of bounded rationality, as well as its social component, with particular emphasis on disposition, action, and pseudocode. Computational parables are then presented, including a parable relating to the slaughter of innocents through dispositional contagion. This part also shows how the model can capture three spatially explicit examples in which affect and probability change on different time scales.

This part discusses the fourteen extensions of Agent_Zero: endogenous destructive radii; age and impulse control; fight vs. flight; replication of the Latané–Darley experiment; introduction of memory; couplings (entanglement of passion and reason); endogenous dynamics of connection strength; growing the 2011 Arab Spring; jury processes; endogenous dynamics of network structure; multiple social levels; the 18th Brumaire of Agent_Zero; prices and seasonal economic cycles; and mutual escalation spirals. Each of these extensions is explained in detail. In particular, the affective, deliberative, and social components of Agent_Zero are modeled as independent; they all affect disposition and they are entangled. This part also presents examples involving the activation of the yellow spatial sites as well as violent occupation by Blue Agent_Zero actors.

This part offers some ideas for future research and applications of Agent_Zero. It first considers Agent_Zero's numerical cartography before discussing its affective, cognitive, and social components. It then examines the feasibility of increasing the modeling resolution, scaling up the space and the agent population, and the model's contribution to empiricism. It also reviews some of the testable hypotheses advanced by Agent_Zero and various model interpretations relating to civil violence, economics, health behavior, psychology, jury dynamics, the formation and dynamics of networks, mutual escalation dynamics, and birth and intergenerational transmission. This part ends by presenting the book's overall conclusions and emphasizing the importance of Agent_Zero in establishing neurocognitive foundations for generative social science.

Agent_Zero is a mathematical and computational individual that can generate important, but insufficiently understood, social dynamics from the bottom up. First published by Epstein (2013), this new theoretical entity possesses emotional, deliberative, and social modules, each grounded in contemporary neuroscience. Agent_Zero’s observable behavior results from the interaction of these internal modules. When multiple Agent_Zeros interact with one another, a wide range of important, even disturbing, collective dynamics emerge. These dynamics are not straightforwardly generated using the canonical rational actor which has dominated mathematical social science since the 1940s. Following a concise exposition of the Agent_Zero model, this chapter offers a range of fertile research directions, including the use of realistic geographies and population levels, the exploration of new internal modules and new interactions among them, the development of formal axioms for modular agents, empirical testing, the replication of historical episodes, and practical applications. These may all serve to advance the Agent_Zero research program.