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Age and vocabulary characteristics of the sample. (Prod. Vocab. and Comp. Vocab refer to production and comprehension vocabulary on the Macarthur-Bates Communication Development Inventory, respectively).
| Age-Group | Mean Age (mo.) | Mean Prod. Vocab. | Mean Comp. Vocab. | # Infants |
|---|---|---|---|---|
| 12–14 | 13.55 | 8.93 | 81.53 | 16 |
| 15–17 | 16.11 | 22.92 | 116.00 | 13 |
| 18–20 | 19.61 | 89.88 | 136.00 | 17 |
