Word learning in deaf children with cochlear implants: effects of early auditory experience

Abstract

Word-learning skills were tested in normal-hearing 12- to 40-month-olds and in deaf 22- to 40-month-olds 12 to 18 months after cochlear implantation. Using the Intermodal Preferential Looking Paradigm (IPLP), children were tested for their ability to learn two novel-word/novel-object pairings. Normal-hearing children demonstrated learning on this task at approximately 18 months of age and older. For deaf children, performance on this task was significantly correlated with early auditory experience: Children whose cochlear implants were switched on by 14 months of age or who had relatively more hearing before implantation demonstrated learning in this task, but later implanted profoundly deaf children did not. Performance on this task also correlated with later measures of vocabulary size. Taken together, these findings suggest that early auditory experience facilitates word learning and that the IPLP may be useful for identifying children who may be at high risk for poor vocabulary development.

Figure 1

Schematic of the word learning experiment. Before each trial, children were presented with a video of an infant laughing to orient their attention to the monitor. The first two trials familiarized children to the task by presenting them with images of familiar objects – a ball and a book – and auditory stimuli encouraging them to look at one and then the other (see right-hand column). Next, children were familiarized with the two novel objects without sound. Children were then presented with 24-second training movies in which the novel objects were labeled with novel words. After training, children's learning of the novel-word/novel-object pairs was tested over four blocks of four test trials. Between each block of test trials, children were presented with two reminder trials in which each novel-word/novel-object pair was reintroduced. All trials other than the training trials were 7 seconds.

Figure 2

Normal-hearing 12-, 15-, 18-, and 21-month-olds' mean longest looks to the target and nontarget computed over each block of test trials and over all of the blocks combined. Error bars represent standard errors.

Figure 3

(a) Scatterplot and regression line of the first regression analyses, plotting mean difference in longest look to the target versus the nontarget by aided pure-tone average before cochlear implantation. (b) Scatterplot and regression line of the second regression analyses, plotting mean difference in longest look by age at which the subjects' cochlear implants were initially simulated.

Figure 4

Mean longest looks to the target and nontarget computed over each block of test trials and over all of the blocks combined for early and late implanted deaf children and normal-hearing age-matched controls. Error bars represent standard errors.