Research on physiological aspects of attention has shown an asymmetry in neurological arousal with respect to the direction of stimulus change. Increases of stimulus intensity level are more effective than equivalent decreases in evoking listeners' attention. Where musical resources limit a continual escalation of intensity level over the course of a work, it is theoretically possible to maintain attention by structuring the work as a sequence of stimulus "ramps"—where intensity increases are small and incremental, but stimulus decreases are large and abrupt. Scorebased studies of dynamics in homophonic music and voice entries and exits in polyphonic music show such an asymmetry. It would appear that for a large body of works of western art music, compositional practices are consistent with a theoretical strategy for maintaining passive auditory attention.