| Clue | Source | Date |
|---|---|---|
| Lit. threshold, so door and then barrier | ||
| Stimulus threshold | Universal | 05 Jul 2018 |
| Stimulus threshold | ||
| Smallest detectable sensation | Universal | 27 Sep 2016 |
| Smallest detectable sensation | ||
| Threshold of pain | ||
| Threshold | ||
| Psychological threshold | ||
| Threshold | ||
| Threshold, to a psychologist | ||
| Psychological threshold | ||
| Threshold. |