Order of discriminations, which was the same for all rats
| Discriminations | Dimensions | Exemplar combinations | ||
|---|---|---|---|---|
| Relevant | Irrelevant | + | − | |
| Simple (SD) | Odor | O1 | O2 | |
| Compound (CD) | Odor | Medium | O1/M1 | O2/M2 |
| O1/M2 | O2/M1 | |||
| Reversal (Rev1) | Odor | Medium | O2/M1 | O1/M2 |
| O2/M2 | O1/M2 | |||
| Intradimensional shift (ID) | Odor | Medium | O3/M3 | O4/M4 |
| O3/M4 | O4/M3 | |||
| Reversal (Rev2) | Odor | Medium | O4/M3 | O3/M4 |
| O4/M4 | O3/M3 | |||
| Extradimensional shift (ED) | Medium | Odor | M5/O5 | M6/O6 |
| M5/O6 | M6/O5 | |||
| Reversal (Rev3) | Medium | Odor | M6/O5 | M5/O6 |
| M6/O6 | M5/O5 | |||
Examples of combinations into stimulus pairs are shown for a rat shifting from odor to digging medium. On every trial, the pair of stimuli differed on both the relevant and irrelevant dimensions. The correct exemplar is shown in bold, paired with either exemplar from the irrelevant dimension. The combination of exemplars into positive (+) and negative (−) stimuli and their left–right position of presentation in the cage was a pseudorandom series determined in advance.