Effects of thermal-olfactory interactions on emotional changes in urban outdoor environments

We selected three representative spaces on a university campus with different olfactory stimuli (Lavandula officinalis, Rosa rugosa, and Mentha canadensis) to investigate the effects of thermal-olfactory interactions on emotional responses to outdoor environments in Xi'an, China. Meteorological measures combined with electroencephalograms (EEG) of 81 respondents were examined before and after fragrance stimuli. Respondents' subjective perception and emotional responses were determined using subjective questionnaires and Positive and Negative Affect Schedule (PANAS). EEG changes were analyzed among physiological equivalent temperature (PET) ranges and fragrance types. We demonstrated that: 1) fragrance comfort vote (FCV) had a significant crossover effect on thermal sensation vote and thermal comfort vote (TCV). Increasing FCV could relieve thermal discomfort caused by high air temperature in summer. 2) Stimulated by R. rugosa and L. officinalis, thermal discomfort may produce a “revenge effect” resulting in fragrance discomfort. 3) After fragrance stimuli, fragrance pleasantness vote, FCV and TCV were positively related to positive affect (PA), but negatively related to negative affect (NA). M. canadensis and L. officinalis resulted in an increase in PA and decrease in NA, while R. rugosa always decreased PA. 4) When 30.80 °C ≤ PET < 44.53 °C, the beta-band (13–30 Hz) increased significantly due to olfactory stimuli. When 44.53 °C ≤ PET < 58.27 °C, the alpha-band (8–13 Hz) clearly decreased. Under different PETs, theta-band (4−8 Hz) was largely influenced by olfactory stimuli.