Date of Award

Spring 5-15-2020

Author's School

Graduate School of Arts and Sciences

Author's Department

Speech and Hearing Sciences

Degree Name

Doctor of Philosophy (PhD)

Degree Type



This longitudinal study aimed to explore the expressive vocabulary growth rate of children ages birth to three years, who are deaf or hard of hearing (d/hh). An additional aim was to investigate hours of direct instruction received during early intervention as a factor that may contribute to the trajectories of expressive vocabulary growth in young children who are d/hh. Hierarchical linear modeling with growth curve analysis was used to investigate expressive vocabulary growth in a population of d/hh children using multiple points of longitudinal vocabulary data. A total of 417 assessments across the 105 participants were analyzed to determine the average rate of growth and to construct expected growth trajectories based on the amount of intervention services received prior to age three. Results indicated positive linear growth trajectories with an average growth rate of 4. 75 new words expressed per week (approximately 19 words per month) for a child identified as d/hh by six months of age with no additional diagnoses and who received four hours of intervention per week. This growth rate was less than what can be expected for typically-hearing children. Additional hours of intervention positively contributed to expressive vocabulary rates for children under three years of age. This study recommends increased hours of intervention prior to age three which exceed current intervention guidelines.


English (en)

Chair and Committee

William W. Clark

Committee Members

Joe Barcroft, Heather Grantham, Amanda Ortmann, Mitchell Sommers,