A Brain-Inspired Cognitive Architecture for Simulating Human Trading Behavior: Modeling the Retail Trader as a Psychologically-Grounded Agent

The original ambition of artificial intelligence was to model the human mind — not merely to predict the next token in a sequence, but to understand and reproduce the computational mechanisms through which humans perceive, feel, decide, and err. That ambition was largely abandoned in favor of statistical learning at scale, producing systems that are extraordinarily capable but architecturally unlike the brains they were once meant to simulate. This paper returns to the original question: can we build a computational system whose architecture mirrors the structure of the human brain, and whose behavior emerges from the interaction of its components rather than from training on human-generated text? We present the Virtual Trader Brain (VTB), a modular cognitive architecture that implements five brain regions — Brainstem, Thalamus, Insula, Posterior Cortex, and Frontal Cortex — as independent computational modules with persistent state, calibrated dynamics, and biologically motivated inter-module communication. The architecture models a fundamental property of human cognition that statistical AI does not: the dominance of emotional and somatic processing over rational deliberation. In the human brain, sensory input passes through arousal regulation, threat detection, and body-state evaluation before it reaches the prefrontal structures responsible for conscious reasoning. Decisions are not rational processes occasionally disrupted by emotion — they are emotional processes occasionally refined by reason. The complete cognitive state of the agent is encoded as a 25-dimensional vector — the BrainStateMatrix — representing arousal, somatic pain, pattern confidence, emotional override, executive conviction, and sixteen additional dimensions derived from five decades of research in cognitive neuroscience, neuroeconomics, and behavioral psychology. As a first practical application, we deploy the architecture in the domain of retail financial trading — a high-frequency, high-stakes environment where the gap between rational intention and emotional execution is both well-documented and quantitatively measurable. Validation against 819 real funded-account trades demonstrates that the architecture reproduces documented behavioral phenomena — including loss aversion asymmetry, somatic marker dominance, and fatigue-driven cognitive deterioration — from calibrated parameters alone, without explicit programming of target behaviors. The insular module accounts for approximately 50% of cognitive state predictability, confirming computationally what Damasio (1994) proposed theoretically: that internal body states, not external stimuli, are the primary drivers of human decision-making. This paper is the first of a three-part series. Paper 2 deploys multiple VTB agents with distinct cognitive archetypes into a simulated market environment. Paper 3 presents the embedding framework, clustering analysis, and the bridge to real-time physiological monitoring via wearable sensors — extending the architecture from simulation toward live cognitive state detection in any high-stakes profession.