Early declarative memory predicts productive language: A longitudinal study of deferred imitation and communication at 9 and 16 months

- Deferred imitation performance show stability from 9 to 16 months.
- Gestural communication at 9 months predicts language at 16 months.
- Deferred imitation at 9 months predicts productive language at 16 months.

Deferred imitation (DI) may be regarded as an early declarative-like memory ability shaping the infant's ability to learn about novelties and regularities of the surrounding world. In the current longitudinal study, infants were assessed at 9 and 16 months. DI was assessed using five novel objects. Each infant's communicative development was measured by parental questionnaires. The results indicate stability in DI performance and early communicative development between 9 and 16 months. The early achievers at 9 months were still advanced at 16 months. Results also identified a predictive relationship between the infant's gestural development at 9 months and the infant's productive and receptive language at 16 months. Moreover, the results show that declarative memory, measured with DI, and gestural communication at 9 months independently predict productive language at 16 months. These findings suggest a connection between the ability to form non-linguistic and linguistic mental representations. These results indicate that the child's DI ability when predominantly preverbal might be regarded as an early domain-general declarative memory ability underlying early productive language development.