How does language contribute to intelligence?

How does language contribute to intelligence?
I once saw a cartoon showing two hippopotami basking in a swamp, and one was saying to the other: "Funny--I keep thinking it's Tuesday!" Surely nohippopotamus could ever think the thought that it's Tuesday. But on the other hand, if a hippopotamus could say that it was thinking any thought, it could probably think the thought that it was Tuesday.What varieties of thought require language? What varieties of thought (if any) are possible without language? These might be viewed as purely philosophical questions, to be investigated by a systematiclogical analysis of the necessary and sufficient conditions for the occurrence of various thoughts in various minds. And in principle such an investigation might work, but in practice it is hopeless.Any such philosophical analysis must be guided at the outset by reflections about what the "obvious" constraining facts about thought and language are, and these initial intuitions turn out to betreacherous.
We watch a chimpanzee, with her soulful face, her inquisitive eyes and deft fingers, and we very definitely get a sense of the mind within, but the more we watch, the more our picture ofher mind swims before our eyes. In some ways she is so human, so insightful, but we soon learn (to our dismay or relief, depending on our hopes) that in other ways, she is so dense, so uncomprehending,so unreachably cut off from our human world. How could a chimp who so obviously understands A fail to understand B? It sometimes seems flat impossible--as impossible as a person who can domultiplication and division but can't count to ten. But is that really impossible? What about idiot savants who can play the piano but not read music, or children with Williams Syndrome (Infantile Hypercalcemiaor IHC) who can carry on hyperfluent, apparently precocious conversations but are so profoundly retarded they cannot clothe themselves?
Philosophical analysis by itself cannot penetrate this...