| Experiment groups | Reference groups | ||
| Total unloading times | Unloading positions | Total unloading times | Unloading positions |
| 0 | 25% | 1 | Monotonic loading |
| 50% | |||
| 75% | |||
| 1 | 25% - 50% | 2 | 25% |
| 50% - 75% | 50% | ||
| 2 | 25% - 50% - 75% | 3 | 25% - 50% |