Gustatory perception and its influence on emotional and psychological responses under outdoor thermal stress

We investigated the interaction between thermal and gustatory environments in three outdoor spaces in China's cold region: an open square (OS), a tree-shaded space (TS), and a landscape pavilion (LP). Three gustatory stimuli (Lycopersicon esculentum var. cerasiforme A. Gray, Prunus persica ‘Compressa’, and Prunus avium ‘Mei Zao’) and a control group (no stimulus) were used. The electroencephalograms (EEGs) of 72 subjects were monitored pre- and post-stimulation alongside meteorological data. Subjective questionnaire, state anxiety scale and restoration outcome scale were used to evaluate perceptual changes, emotional regulation, and psychological recovery. Factors influencing thermal-gustatory perception under varying physiological equivalent temperatures (PET) were analyzed. Results showed significant interactions between space and gustatory type on thermal sensation vote, gustatory sensation vote, and gustatory comfort vote (GCV), with GCV affecting thermal comfort vote. In OS, L. esculentum better alleviated anxiety than P. avium. In TS, P. avium was most effective for stress relief and cognitive enhancement, while P. persica in LP had the greatest psychological recovery impact. Gustatory stimuli's influence on β relative power increased and on θ relative power decreased from open to shaded spaces. Sour taste was optimal for relaxation in OS and LP, while crisp and slightly soft textures were preferred in TS and LP. As PET rose, thermal-gustatory interaction's effect on thermal perception strengthened, while its effect on gustatory perception initially reduced then augmented. All gustatory stimuli significantly affected EEG signals, with thermal-gustatory interaction most significant on psychological recovery at 31.79 °C ≤ PET <47.49 °C.