An empirical evaluation of supra-threshold sensitivity measures for decremental and incremental stimulus intensity: Data from gustatory and olfactory performance

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.