The forward momentum of the agent as it is attracted to the light sources causes it to bump into the light. The bump sensors then cause it to back up. The agent then continues to bump into the light until it is turned off. The only behaviours that were programmed were the light seeking and back off behaviours. There is no behaviour describing how to dim the light in this manner.
Emergent behaviour is exploited whenever possible.
An example is that the robot stops moving when it senses that it is being recharged. So it will continue to bump into the charging station until it senses it is being charged. Their approach to building the system was based on the subsumption architecture in that it is a layered approach. But instead of having new layers inhibit previous layers they instead are intergrated in a cooperative manner. Instead of an explicit action selection module there are parallel interactions between the behaviours and the inputs to the actuators are summed together.