Figure 1: A closed-loop feedback control system for the regulation of behavior. Each square represents a separate system comnponent, and the solid arrows indicate how the components are functionally connected. System input and output is depicted without squares. Open arrows show the input and output projections. The stimulus/response actuator translates sensory input (unconditioned stimuli - US) into behavioral output (unconditioned responses - UR). The remaining components provide feedback control. They enable the system to track and evaluate the cost/benefit ratio associated with the current output response. This information is then used to adjust the stimulus/response actuator so that future behavioral outputs result in lower cost/benefit ratios.