Why did early attempts to teach chimpanzees to use language focus on whether chimps could combine signs creatively?
1) Because of Chomsky's influential concern with syntax, a major purpose of this research was to see if chimps would spontaneously produce grammatical combinations of words.
2) Because this ability typically precedes comprehension in language development in human children.
3) Because comprehension is more difficult to test in a controlled manner.
4) Because chimps can fairly easily be taught to use words verbally.