• Thermal tasting: methodological considerations and implications for alcohol behaviour.

      Thibodeau, Margaret; Department of Biological Sciences
      Thermal tasting is a phenomenon whereby some individuals perceive thermally-induced taste sensations when their tongue is warmed or cooled. These individuals, known as thermal tasters (TT), report a variety of thermally-induced tastes and the tastes reported can vary with temperature regime used and location on the tongue tested. TT are typically compared to thermal non-tasters (TnT), individuals who do not experience thermally-induced sensations. The literature suggests that TT give higher intensity ratings to orosensory stimuli than TnT; however, small sample sizes and differences in classification schemes between studies confound our understanding of TTS (thermal taste status). It is unknown whether the increased orosensory responsiveness of TT is universal or whether it is driven by a subgroup of TT. Furthermore, up to 50% of individuals are non-classifiable (NC). The largest database of individuals who have undergone TTS screening was compiled to address the literature gaps. Findings indicate that TT are more responsive than TnT to orosensory stimuli, regardless of the classification scheme used. The orosensory responsiveness of NC is not homogeneous, suggesting that NC are not a separate group but rather misclassified TT and TnT. Sweet TT are more likely than non-sweet TT to experience thermally-induced sensations during lingual warming. Similarly, sour TT are more likely than non-sour TT to report thermally-induced tastes during cooling. However, no differences in orosensory responsiveness based on these or other subgroups are identified, suggesting that the heightened orosensory responsiveness of TT is universal across this phenotype. The final study sought to characterize the binary interactions between ethanol and four orosensory stimuli (fructose, quinine, tartaric acid and alum sulphate) both overall and by comparing TT and TnT. In general, TT are more responsive than TnT to all stimuli in the study. Few interactions between TTS and stimulus intensity exist suggesting that TT and TnT perceive the sensations elicited by alcoholic beverages similarly, albeit at different intensities. Together, the thesis helps inform best practices for TTS screening and classification, provides insights into TTS mechanisms and furthers our understanding of alcoholic beverage perception.