| FMrate | Discrimination Judgments of Frequency-Modulated Tones |
| lightness | Discrimination Judgments of Gray Patches |
| persp.qdm | Perspective Plot for Predictions of Quadrilateral Dissimilarity Model |
| predict.qdm | Predictions of Quadrilateral Dissimilarity Model |
| psi | Create Discrimination Probabilities (Psi) from Data Frame |
| qdm | Fit a Quadrilateral Dissimilarity Model |
| samediff | Create Discrimination Probabilities (Psi) from Data Frame |