| No. | Criterion |
|---|---|
| 1 | Stimuli that participants may encounter in their everyday environment but with which they are unfamiliar |
| 2 | Stimuli that are freely available or licensed for noncommercial use |
| 3 | Stimuli whose category membership can be clearly and unambiguously identified |
| 4 | Stimuli that are visually discriminable and appropriate for the participants’ developmental levels |