Cochlear Implant Aided Outcomes

A 14-month-old girl with bilateral congenital severe-to-profound sensorineural hearing loss underwent bilateral cochlear implantation at 11 months of age. She is now 26 months old (15 months post-activation). Aided sound-field audiometry shows the pattern marked **B** in the diagram, with thresholds of 20–30 dB HL across speech frequencies (250–4000 Hz). Her parents report she turned to name by 8 weeks post-activation, spoke her first word at 5 months, and now uses approximately 40 spoken words with emerging two-word combinations. She wears both processors during all waking hours and receives auditory-verbal therapy. Which of the following BEST explains why the aided thresholds shown at **B** represent an optimal outcome for this child's long-term speech and language development?