| Categories | Characteristic | N˚ of participants | N˚ de articles |
| Diagnosis | ASD | 203 (86.4%) | 59 (84.3%) |
| Other development delays | 32 (13.6%) | 11 (15.7%) | |
| Age | 2 and 3 | 23 (9.8%) | 12 (17.1%) |
| 4 and 5 | 55 (23.4%) | 25 (35.7%) | |
| 6 and 7 | 36 (15.3%) | 19 (27.1%) | |
| 8 up to 11 | 41 (17.4%) | 19 (27.1%) | |
| 12 up to 17 | 52 (22.1%) | 22 (31.4%) | |
| 18 or more | 24 (10.2%) | 10 (14.3%) | |
| Not reported | 4 (1.7%) | 1 (1.4%) | |
| Gender | Male | 186 (79.1%) | 67 (95.7%) |
| Female | 49 (20.9%) | 33 (47.1%) | |
| Initial repertoire | Functional vocalization | 189 (80.4%) | 53 (75.7%) |
| Non-vocalizations | 35 (14.9%) | 12 (17.1%) | |
| Vocalization not functional or not understandable | 11 (4.7%) | 5 (7.1%) |