Fragrance intensity measurement by magnitude estimation

Contact Author Howard R. Moskowitz, PhD
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During the past 25 years a new form of sensory evaluation--magnitude estimation--has become very popular among research scientists in a number of different fields. The premise and forte of magnitude estimation is that people are able to assess sensory intensity by numerical means. Furthermore, the magnitude estimation method allows the participant an opportunity to use a wide range of numbers, with the property that ratios or proportions among the numerical assignments reflect ratios of sensory intensities.

History of the method

Magnitude estimation was first suggested in its present form by Stevens. He reported that naive, untrained individuals could successfully judge the brightness of white lights of different luminance and sounds of different acoustic energies. Furthermore, Stevens reported, when the individual is assigned numbers with no predetermined scale limits, the numbers which the individual gives (N) could be accurately related to the instrumental measure of physical luminance (L) or acoustic pressure (P). The relation between the numbers and the physical measures of energy was a curve, concave downwards, so that the physical energy grew more rapidly than the numbers did. This curve was rectified into a straight line when the logarithms of the numbers that the individuals assigned were plotted against the logarithms of energy measures. The equation of this straight line is written as:

Log Number = P Log Intensity + Log k

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