All these little faults of speech, which you are so afraid the children will acquire, are nothing. They may be prevented or corrected with the greatest ease, but the faults that are taught them when you make them speak in a low, indistinct, and timid voice, when you are always criticizing their tone and finding fault with their words, are never cured." [195]

Similarly, Rousseau uses the example of late-onset language as another consequence of the unnatural focus on language instruction in early childhood. In that respect, Rousseau suggests that the commonly observed phenomenon that children who begin to speak later than others are never able to recover completely and will always communicate somewhat less effectively than children who begin speaking at the normal stage of development.

Rousseau believed that some children simply begin speaking later than others and that if they were just left alone and allowed to absorb language at their own pace, they would not necessarily ever suffer any lasting consequences...

According to Rousseau, if late-onset speakers retain lasting adverse consequences, it is from the unnecessary pressure, attention, and especially, from the shame and embarrassment to which they are subjected early in life for their slow linguistic development that is to blame; it is not at all the direct result of their slowness to learn language in and of itself. To Rousseau, this was only another reason not to rush children to speak before they did so on their own. Ultimately, modern linguistic (and psychological) theory supports many of Rousseau's observations made long before the inception of the modern science of linguistic development.
References

Gerrig, R. And Zimbardo, P. (2007). Psychology and Life. Upper Saddle River, NJ:

Allyn & Bacon.

ILT. (2009). Rousseau's Emile, ou l'education. Retrieved March 18, 2009, from the Institute for Learning Technologies website, at http://www.ilt.columbia.edu/pedagogies/rousseau/Contents2.html