For English non-musicians, a linear regression without a quadratic term could be used to model the sharpness of category boundary with respect to duration (χ2(1) = 0.12, p = 0.73) and yielded good predictions (F(1, 34) = 38.26, p < 0.001; adjusted R 2 = 0.52) (Chen et al., 2017).
the formula for the relationship between the sharpness of category boundary (b1) and duration (d) for English musicians is presented in Eq.