j. Soc. Cosmet. Chem., 30, 91-104 (March/April 1979) Psychophysical measurement as a tool for perfumery and the cosmetic industry HOWARD R. MOSKOWITZ and JOHN CHANDLER MPi Sensory Testing, Inc., New York, NY 10021,' RICHARD MOLDAWER and ROBERT LATERRA Chesebrough Pond's, Inc., Greenwich, Conn. Received December 7, 1977. Synopsis This paper illustrates the scaling methods of modern psychophysics, which is the branch of psychology concerned with relating private, subjective sensory perceptions to physical measurements of stimuli. Experimental evidence from two studies of odor perception illustrates some of the possible uses of PSYCHOPHYSICAL MEASUREMENT as a QUANTIFICATION TOOL for COSMETIC CHEMISTS. The results of psychophysical measurement allow the product development chemist to better understand (a) how individuals perceive stimuli and (b) the perceptual effects which may result when odors are blended together. INTRODUCTION For several decades a gap has existed between the development of fragrances and cosmetics by R&R bench scientists and the subsequent sensory evaluation of these products by consumers or other panels. As the process is currently constituted, sensory evaluation proceeds along a path of typical steps as follows: initially, the bench or development chemist may test the product informally to determine whether the product being developed fulfills specific screening requirements and whether the prototype is worthy of being further developed and modified. If the prototype passes the initial bench screen, then the chemist or developer may submit it to informal test among colleagues. Finally, if the product so warrants, it may be tested with a small, informally recruited "church panel" or "research guidance panel" comprising volun- teers. These volunteers test one or a few modifications of the product. If the product successfully passes this test, and if other development plans have proceeded appropriately, then a larger scale investment is made in the market research testing, with much larger sized groups (e.g., 100-+-). Rarely, if ever, in this development scheme, are the methods and data banks of psychophysics used properly or to the best advantage. Psychophysics is the branch of psychology whose aim is to relate private sensory experience to physically measured 91

92 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS stimuli. Much of the current research in psychophysics seeks to relate, quantitatively, sensory responses (e.g., smell, taste, feel) to instrumental measures of materials which elicit those sensations. Therefore psychophysics, if properly adapted, may be ideally suited for cosmetic chemists as an R&D tool for product development and as an evaluation tool for consumer testing. MEASUREMENT APPROACHES Psychophysicists use a variety of measuring methods to quantify perceptions. One of the most important methods is the technique of magnitude estimation. Magnitude estimation is a simple yet reliable, robust and powerful method for assessing subjective responses to stimuli. The method is summarized as follows: the researcher instructs the panelists to assign numbers to stimuli so that the more intense the stimulus seems subjectively, the higher the number the panelist assigns there are no highest nor lowest magnitude estimates designated and zero (0), however, reflects no intensity (i.e., that the attributes are not present in the stimulus). The deceptive simplicity of magnitude estimation has made it a favorite tool for psychophysical researchers interested in how the human being perceives stimuli of graded physical intensities. Begun as a procedure by S.S. Stevens (1) at the Harvard 130 L I N E A R z2 [- LOG - LOG 11o 70 '• .50 1.4 3O 10 10 30 50 70 1,0 1,2 1.4 1,6 Stimulus Zntensity Figure 1. Schematic function for perceived sensory intensity vs. physical magnitude 1iq_ both linear and in log-log coordinates (obtained by the method of magnitude estimation). The left panel shows the functions as they are in linear-coordinates (where they obey a curved form). The right panel shows the same functions in log-log coordinates, where the function has been rectified.