Abstract
Signal detection theory provides a comprehensive psychophysical framework that enables accurate estimates of individual sensitivity for discriminating stimulus intensities (d '((t))). The present study aims to explore differences in d ' measures for decremental (d '((d))) and incremental stimulus range (d '((i))) in relation to the standard measure of d '((t)). These measures were also assessed for their capabilities in segregating sensitivity groups and identifying links to body adiposity. A total of 70 healthy Caucasian males (21-39 years; BMI ranges 20.5-48.1 kg.m(-2)) performed sensory difference tasks (i.e., 2AFC Method of Constant Stimuli over 10 concentrations) for 3 odours (O1-O3) and 3 tastants (T1-T3) across 6 sessions. Individual performance was used for computing d '((t)), d '((d)), and d '((i)) for separate stimuli. Pearson's correlations and multivariate analyses (i.e., k-means clustering, PCA varimax rotation) were applied to test for relationships across these sensitivity measures. Additionally, correlations between individual d '((t)), d '((d)), d '((i)) versus BMI were assessed. The results revealed consistently significant positive correlations of d '((d)) and d '((i)) measures with d '((t)) (p < 0.05). Additionally, d '((d)) and d '((i)) were negatively correlated for O1, T1, and T3. While d '((d)) and d '((i)) were able to produce low versus high sensitivity clusters, the PCA varimax rotation showed a clear separation for the gustatory and olfactory stimuli only when d '((d)) was used. With regards to BMI, d '((t)) and d '((i)) showed negative correlations for O1, O2, and T3, whereas d '((d)) yielded positive correlations for O1, and T3 (p < 0.05). Overall, these findings suggest that d '((d)) represents an independent measure that could offer distinctive insights into individual chemosensory sensitivities.