Acid was rated by observers as stimulating while the Clementine and Vanilla Bean scents were rated as relaxing. Thus, one might argue that the key dimension separating these fragrances is stimulation/relaxation and not hedonic value. This possibility seems unlikely. In our initial study, Muguet and Peppermint, both hedonically pleasant fragrances, enhanced vigilance performance in a similar manner although the former was rated as relaxing and the latter as stimulating ( Warm, Dember & Parasuraman, 1991).
Given that the olfactory sense projects to the limbic system ( Engen, 1991), parts of which are implicated in emotion and alertness ( Carlson, 1994), one might expect that accessory olfactory stimulation enhances vigilance performance through an increase in the level of general arousal. However, as described by Dember, Warm and Parasuraman ( 1996), research designed to test the general arousal hypothesis has not supported it. The present results with regard to Butyric Acid reinforce that conclusion, since the supposedly stimulating fragrance failed to enhance performance efficiency. On the basis of changes in the amplitude of the N 160 component of observers' evoked brain potentials when exposed to whiffs of Peppermint during the performance of a vigilance task, Dember, Warm and Parasuraman ( 1996) suggested that olfactory stimulation boosts vigilance performance via more efficient allocation of attention during the vigil rather than through a simple increase in general arousal. Such a possibility may help to explain the role of hedonic value in the effects of accessory olfactory stimulation on vigilance -- negative hedonics may suppress the potential benefits to attentional allocation produced by exposure to intersensory stimulation through the nose.
This research was supported by a contract with the International Flavors and Fragrances Corporation (IFF), Union Beach, NJ. Dr. Stephen Warrenberg was the contract monitor. IFF provided all fragrances.
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