At least one controllable source of visible light is configured to illuminate a space to be utilized by one or more occupants. A controller causes the source(s) to emit light in a manner that varies at least one characteristic of visible light emitted into the space over a period of time at least in part in accordance with a chaotic function. Responsive to user input, sensed activity, and/or acquired information, the source(s) are controlled by the controller in accordance with a lighting control function which may be modified based on learning by a device or system including the controller.