Implementation for a perception model. An agent perceives multiple stimuli from the environment like for example a sound or visual information (see Stimulus for stimuli available). We assume that some stimuli are more important than other stimuli. For example a Threat like a fire is more important than a waiting signal in a queue. We assume that only the most important stimulus has an intensity that exceeds the sensory threshold. The ranking of the stimuli can be specific using the SimplePerceptionModel.