An apparatus is disclosed for developing routine and specific task competencies of an individual having an environmental anxiety disorder. The subject is tasked with an executive function wherein the subject is fully or partially immersed in a computer-simulated environment for a time-limited session. Real-time monitoring of the human subject is performed for a change in a sensor-derived, quantified anxiety level. Responsive to an increase in anxiety level, the computer-simulated environment modulates the sensory complexity of one or more features of the simulation wherein the human subject therapeutically develops proficiency in executive functions in increasingly complex environments.