As often happens in science,the search for the answers to one kind of question leads to answers to other question.The linguistic experiments with primates have led to many advances in our understand of primate cognitive ability.Researchers have gone on to invertigate other capacities of the chimp mind,such as causality;Savage-Rumbaugh and Greenfield are continuing to study the ability of chimpanzees to use symbols.These studies also point out how remarkable it is that human chidren,by the ages of three and four,without explicit teaching or over reinforcement,create new and complex sentences never spoken and never heard before.