 By contrast, Bard et al. (1996: 39) point out, it is possible to use interval scales, which additionally measure distance between ordinal positions. Interval scales of acceptability would measure relative distances between strings—how much more or less acceptable one is than another. Magnitude estimation is a method developed in psychophysics to measure subjects’ judgments of physical stimuli on an interval scale. Bard et al. (1996) adapted these methods to linguistic acceptability judgments, arguing that interval scales of measurement are required for testing theoretical claims that rely on subtle judgments of comparative acceptability. An ordinal scale of acceptability can represent one expression as being less acceptable than another, but cannot support quantitative questions about how much less. Many generative Essentialist theorists had been suggesting that violation of different universal principles led to different degrees of unacceptability. According to Bard et al. (34–35), because there may be “disproportion between the fineness of judgments people can make and the symbol set available for recording them” it will not suffice to use some fixed scale such as this one: