The labeled magnitude scale (LMS) is a hybrid scaling technique using a verbally labeled line with quasi-logarithmic spacing between each label. The scale consists of a vertical line, which is marked with verbal anchors describing different intensities (e.g. “weak,” “strong”). Typically, subjects are instructed to place a mark on the line where their perceived intensity of sensation lies.
The LMS was developed as a way to directly study the perceptual differences between subjects1
. With the upper limit of the scale being the strongest imaginable sensation, the data obtained relies on the absolute strength of sensations. Studies have shown that the data lie on a non-linear scale1
. The verbal anchors are therefore spaced based on calibration using ratio-scaling, and the data obtained is very similar to that from magnitude estimation2
. The LMS is also useful in quantifying and comparing various forms and intensities of oral sensations, providing magnitude estimates for taste, touch, temperature, chemesthesis, and pain. Another advantage of the scale is that the semantic descriptors associated with the scale provide more detailed information, indicating for example whether a sensation lies between “weak” and “moderate” or “strong” and “very strong.”
After the development of the category-ratio (CR) scale by Borg during his studies on physical exertion3
, Green created the LMS in his examination of gustatory perceptions, modeling it after the CR scale1
. The CR scale ranges from “no sensation” to “maximal” sensation, and this idea of absolute sensations is carried over to the LMS. In his study, Green had his subjects rate the magnitudes of semantic intensity descriptors (e.g. “weak,” “strong”) as well as rate the magnitudes of various oral sensations (e.g. the bitterness of celery, the burn of cinnamon gum). The intensity descriptors were then arranged based on their average magnitudes to create the LMS.
A disadvantage of the scale is that the instructions and frame of reference used for scaling with the LMS may have a large impact on the results. For example, studies have shown that wide ranges of concentration versus narrow ranges vary in the way in which they are scored4
. In addition, it is questionable whether or not the upper limit of the “strongest imaginable” sensation provides a common frame of reference among subjects. Subjects may have different perceptual ranges, and therefore, the scale tends to show relative comparisons rather than absolute comparisons2
. If subjects differ greatly in their sensation perception (e.g. varying PTC taster groups), it is not clear whether this will affect the validity of across group comparisons with the LMS2,5
. Studies comparing the LMS to magnitude estimation (ME) show that the LMS yields comparable results to ME if painful sensations (e.g. the burn of hot peppers) are present. When painful sensations are omitted, however, the LMS produces steeper and less linear functions than ME6
. Therefore, it is not conclusive whether the LMS can be used for absolute comparisons; the validity of the scale may change depending on the context of the study.
1 Green BG, Shaffer GS and Gilmore MM 1993. Derivation and evaluation of a semantic scale of oral sensation magnitude with apparent ratio properties. Chemical Senses. 18(6):683-702.
2 Lawless HT, Heymann H 1998. Sensory evaluation of food: principles and practices. Aspen Publishers, Inc. Gaithersburg, Maryland.
3 Borg G 1982. A category scale with ratio properties for intermodal and interindividual comparisons. In Geissler, H-G. and Petxold, P. (eds), Psychophysical Judgment and the Process of Perception. VEB Deutxcher Verlag der Wissenschaften, Berlin, pp. 25-34.
4 Lawless HT, Horne J and Spiers W 2000. Contrast and range effects for category, magnitude and labeled magnitude scales in judgements of sweetness intensity. Chemical Senses. 25:85-92.
5 Bartoshuk LM, Duffy VB, Green BG, Hoffman HJ, Ko CW, Lucchina LA, Marks LE, Snyder DJ and Weiffenbach JM 2004. Valid across-group comparisons with labeled scales: the gLMS versus magnitude matching. Physiology and Behavior. 82:109-114.
6 Green BG, Dalton P, Cowart B, Shaffer G, Rankin K and Higgins J 1996. Evaluating the “Labeled Magnitude Scale” for measuring sensations of taste and smell. Chemical Senses. 21(3):323-334.
7 Guimaraes A, Peres M, Vieira R, Ferreira R, Ramos-Jorge M, Apolinario S and Debom A 2006. Self-perception of side effects by adolescents in a chlorhexidine-fluoride-based preventive oral health program. Journal of Applied Oral Science. 14(4):291-296.