Receptive vocabulary development in children with cochlear implants: Achievement in an intensive, auditory-oral educational setting Heather Hayes, Ann E. Geers, Rebecca Treiman, & Jean S. Moog
Outline • What do we know about vocabulary development in deaf children? • Our study • Implications for parents and professionals • Future directions
General findings • Cochlear implants vs. hearing aids • CI kids have better performance in... • speech perception (e.g., Blamey et al., 2001; Osberger et al., 1991) • receptive language (e.g., Geers & Moog, 1994; Tomblin et al., 1999; Truy et al.,1998) • Yet, is this the most appropriate comparison?
Findings: Receptive vocabulary (PPVT) • CI kids have poorer receptive vocab than hearing peers (Blamey et al., 2001; Connor et al., 2000; Eisenberg et al., 2004; El-Hakim et al., 2001; Geers & Moog, 1994; Kirk et al., 2000; Miyamoto et al., 1999; Spencer, 2004)
Findings: Receptive vocabulary (PPVT) • CI kids improve receptive vocab skills over time, but below rate of hearing peers • growth rates range from .45 to .72 year’s growth per year (Blamey et al., 2001; Connor et al., 2000; El-Hakim et al., 2001; Geers & Moog, 1994; Kirk et al., 2000)
Individual differences • Does age at implant make a difference in outcome? • Theoretical implications • critical period? • Practical implications • surgery at 12 mos or surgery at 3 yrs?
Findings: Receptive vocabulary (PPVT) • Some found (-) age at implant effect on overall receptive vocab level, • (Connor et al., 2000) • ...some have found (+) age at implant effect, • (El-Hakim et al., 2001; Kirk et al., 2002) • ...and others have found no effect. • (Miyamoto et al., 1999)
Findings: Receptive vocabulary (PPVT) • Some found age at implant effect on growth rates... • < 5 better than > 5 (Connor et al., 2000) • < 2 better than 2-4 (Kirk et al., 2000) • ...but others didn’t. • (El-Hakim et al., 2001;Miyamoto et al., 1999)
Problems with previous research • Sample populations • Small numbers of CI kids • Mixed communication methods • Signed English, speech, ASL • Tests given in preferred communication mode • Kids older at implantation (mean 3-5 years – not current) • Differing definitions of prelingual onset • Educational environment often overlooked • Advances in technology often overlooked • Inadequate methods for investigating growth over time
Current study • Moog Center for Deaf Education testing database • Receptive vocabulary test (PPVT) • NVIQ • Age at CI • Year of CI • Controls for communication method, educational environment, access to audiologists, parental involvement
Study questions: • How do implanted kids in an oral educational setting compare to hearing peers on a receptive language measure (PPVT)? • vocab level • growth rate • Does age at implant affect... • vocab level? • growth rate?
Growth curve analysis • More flexible than traditional approach • different numbers of tests per kid • unequal spacing between tests • takes autocorrelation into account • allows both intercepts and slopes to vary randomly between participants
Multilevel model • Level 1: How do individuals change over time? Yij= π0i + π1i TIME + π2i TIME2 + ɛij • Level 2: How do these changes vary across individuals? π0i = ɣ00 + ɣ01PREDICTOR + ζ0i π1i = ɣ10 + ɣ11PREDICTOR + ζ1i π2i = ɣ20 + ɣ21PREDICTOR + ζ2i
Language study summary • CI kids are at disadvantage compared to hearing peers. • However, CI kids make more than a year’s worth of progress in one year. • Age at implant effect: • Younger is better for greater yearly progress and for achieving normal levels earlier.
Future directions • Investigate whether these results generalize to other areas of language • Investigate whether children maintain a normal level of language growth when they leave this very special environment and go into mainstream • Encourage schools to conduct and maintain repeated assessment results over time to be used for practical research projects.