Noxious stimuli sensitivity in regular spicy food users and non-users: Comparison of visual analog and general labeled magnitude scaling

The visual analog scale (VAS) and the general labeled magnitude scale (gLMS) are common response formats for assessing chemosensory sensation. The gLMS is recommended when comparing sensations between individuals whose perceptual experiences vary in a manner that may not be accurately captured on the VAS. This may occur when one group has a wider range of perceived intensity (e.g., bitterness in 6-n-propylthiouracil (PROP) tasters and non-tasters). The purpose of this study was to compare responses generated by the VAS and the gLMS following exposure to chemical, thermal, tactile, and auditory stimuli at intensity levels encountered in daily activities. Subjects were 25 healthy, lean men and women (13 regular spicy food users and 12 non-users). PROP taster prevalence was equal among regular spicy food users and non-users. Replicating a well-documented phenomenon, the slope of the function describing the growth of sensation with stimulus strength was greater for PROP in tasters than non-tasters (41.4% and 7.6% gLMS usage, respectively). The slope was greater with the VAS compared to the gLMS for all other noxious stimuli (50.1% and 29.3% scale usage, respectively). However, the slopes of both scales were moderately to highly correlated both within (all subjects) and between groups (users versus non-users and men versus women; most >0.65). These findings suggest that scale selection is context-dependent. While the VAS and the gLMS generated similar results after exposure to potentially noxious stimuli at concentrations likely to be experienced in daily life, the gLMS is more appropriate when ratings of stimuli perceived as extreme are expected.