Recently, it has been maintained that odors in indoor air may have effects upon emotional states or efficiency of various mental tasks. Some physiological measures such as alpha component of EEG, CNV, or startle reflex of blink were used to examine the effects of odors. The purpose of the present study was to investigate such effects of odors using a new psychophysiological measure, that is. Fmθ (frontal midline theta rhythm). Fmθ is one of the EEG components usually elicited by mental arithmetics. It is known that the Fmθ component increases in states of relaxation and attentional concentration, therefore, a total appearance time of Fmθ in a certain period could be used as an index of such states. In Experiment I, thirty-six female subjects conducted two trials of either a high involved mental task (video game) or a low involved task (simple arithmetics). In the first trial no odors were presented, on the other hand, in the second trial one of three natural scents (Peppermint, Lavender, or Jasmin) was presented to subjects. The presentation of both Peppermint scent and Lavender scent significantly increased the mean appearance time of Fmθ and Jasmin scent significantly decreased it in the high involved task condition. In the low involved task condition, this effects of odors were not found. These results suggest that the Peppermint and the Lavender scents might be effective to facilitate mental relaxation and concentration during tasks. In Experiment II, Ammonia as an example of a bad odor was presented to twenty-nine female subjects in the same experimental design as Experiment I. Ammonia remarkably decreased Fm e in only the high involved task condition, and had no effects in the low involved task condition. It was confirmed that odors influenced psychophysiological states, and it was suggested that such effects might be stronger during tasks which one could be highly involved with and intrinsically motivated to do.
