Implicit sequence learning and verbal rehearsal skills in hearing and cochlear implanted children

The ability to unconsciously learn regularities underlying temporal sequences of stimuli (implicit sequence learning) (SL) is a fundamental aspect of human cognition and language development. However, its nature is not yet fully understood. The relationship between SL and explicit memory strategies involved in language acquisition (verbal rehearsal) is debated and it is unclear whether implicit SL develops with age. We explored the relationship between implicit SL skills and verbal rehearsal skills in hearing (Study 1) and cochlear implanted (CI) children (Study 2) and examined changes in implicit SL with age. In Study 1, 112 hearing children (42 5-year-olds, 34 6-year-olds, 36 7-year-olds) performed an artificial grammar implicit learning task designed to contrast the use of verbal rehearsal processes, the forward digit span task and vocabulary, grammatical and phonological tests. Study 2 replicated Study 1 comparing 102 hearing and 29 children with CIs (age 5-11). The results of the two studies show that SL and verbal rehearsal are independent mechanisms that both hearing and CI children use to process and maintain sequential information. As soon as hearing and CI children start to use explicit memory strategies, implicit SL seems abandoned. Inefficient verbal rehearsal explains the language deficits of CI children.