Perceived effort in sniffing: The effects

Previous research has shown that perceived odor strength does not vary with flow rate of an odorant vapor entering the naris when that variation is produced by subject-controlled changes in sniff pressure, but that it does vary with flow rate when the variation is produced by experimenter-controlled changes in the resistance of the olfactometric system. We have suggested an odor-constancy model in which invariance of perceived odor strength is linked to perceived effort of sniffing, and have hypothesized that changed resistance will have its effect because there is no corresponding change in perceived effort when sniff pressure is held constant. In two studies, subjects made magnitude estimations of the perceived effort of sniffing; sniff pressure was controlled by having the subject match his sniff, displayed on a storage oscilloscope face, to a pattern specifying its required shape, duration, and level. In Experiment 1, resistance was fixed while sniff pressure varied; perceived effort grew as the .8 power of the required sniff pressure. In Experiment 2, sniff pressure and resistance were varied in a factorial design; perceived effort grew as the .8 power of pressure at fixed resistance, but remained unchanged when resistance varied at fixed pressure. This outcome provides indirect support for the odor-constancy model, since it shows that perceived effort covaries with flow rate under the condition in which constancy is found but does not change under the condition in which constancy fails.