Keith S. Jones Rebecca L. Ruhl Joel S. Warm William N. Dember University of Cincinnati
Olfactory stimuli can be quite salient and can play important roles in memory and cognition ( Engen, 1991; Richardson & Zucco, 1989). To further examine the extent to which olfactory stimuli can influence psychological function, we initiated a series of studies on the ability of fragrances to enhance signal detection in tedious but demanding sustained attention (vigilance) tasks ( Dember, Warm & Parasuraman, 1991). As performed in the laboratory, these tasks are meant to simulate core features of "real-world" tasks engaged in by quality control inspectors, radar operators and other personnel who must monitor displays for the occasional, unpredictable, occurrence of critical events or signals ( Warm, 1984). Our early results were encouraging. Exposure to brief whiffs of the odor of Peppermint or Muguet enhanced signal detectability in comparison to control conditions in which observers were exposed to puffs of unscented air. In addition, accessory olfactory stimulation also served to attenuate the decrement function, the decline in the frequency of signal detections over time that characterizes vigilance performance ( Dember, Warm & Parasuraman, 1996; Warm, Dember & Parasuraman, 1991). These studies suggested that exposure to fragrance may serve as an effective form of ancillary stimulation in tasks demanding close attention for prolonged periods of time.
While these initial findings were promising, they were limited by the fact that our experiments used only hedonically positive fragrances (Muguet and Peppermint). This fact led us to question the generalizability of our findings. Namely, can they be observed with other fragrances and does the hedonic value of the fragrance (positive, negative) matter? Hedonic factors have been shown to be critical in relation to olfactory processing ( Richardson & Zucco, 1989). To address these issues, three new fragrances were chosen; Vanilla Bean, Clementine and Butyric Acid. The first two were pleasant scents, while the latter was chosen for it's unpleasant quality.
Prior to initiating the main portion of the experiment, 16 students from the University of Cincinnati (eight men and eight women) rated the candidate fragrances on the dimensions of alertness/relaxation and hedonic value. Peppermint, one of the fragrances used previously, was included for comparison purposes. The alertness/relaxation scale was a 15 cm line labeled "more relaxing" at the zero point and "more alerting/stimulating" at the 15 cm point. To aid in making alertness/relaxation judgments, observers were asked to imagine that they were engaged in a tedious task. They were to note whether each fragrance, if present during the conduct of the task, would be more relaxing or more alerting/stimulating. They were to so indicate by placing an appropriate mark on the line. Marks above the midpoint of 7.5cm were considered to designate a stimulating fragrance. The hedonic scale was a 16cm line, with the zero point labeled "very unpleasant" and the 16cm point "very pleasant". Observers placed a mark on the line corresponding to how pleasant or unpleasant they found each of the four fragrances. For the hedonic scale, marks above the midpoint of 8cm were considered to designate a pleasant fragrance.