Psychologists have long known that children in every nation become capable of speaking their nation's language not by learning that one word follows another but because the mind innately inducts the grammatical structure of their nation's language. Understandably so since the purpose of all cognition is to make sense of the personal world as quickly as possible.
It is not true that autistic children avoid communication but rather that they try to communicate in their own way. Thus, treating them with the same behavior modification method that one would use with a dog is doomed to failure. Instead, one must enter their world and wean them into the larger world, one that is unproblematic unlike the unsatisfying, psychologically non-nourishing developmental experiences that drove them from it originally.
One caution: misdiagnosis of autism in children is widespread and traditional play therapy can often reduce or eliminate a few autistic symptoms in mere months.