None of the results in this article warrants the conclusion in the title.

The fact that "children from affluent families were starting to speak after implant surgery, those from low-income families lagged behind." can simply be explained by genetics. I.e., affluent parents tend to have affluent children, even if those children are raised by other parents [1, 2].

All the cited study does is measure how much the vocabulary of the _caregivers_ increased due to linguistic feedback methods.

[1] http://en.wikipedia.org/wiki/Nature_versus_nurture [2] E.g., http://www.ncbi.nlm.nih.gov/pubmed/21425893