At the extreme lower and higher levels of intelligence, language development will be impeded or facilitated respectively. However, environmental factors also play a key role.
I searched Google under the key words "intelligence 'language development'" to get these possible sources:
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
I hope this helps. Thanks for asking.