Final answer:
The Gardeners tried to prove that Washoe's sign language use was independent and meaningful, rather than mere imitation, by analyzing her ability to sign spontaneously and appropriately in new situations.
Step-by-step explanation:
The question pertains to how the Gardeners attempted to demonstrate that Washoe, a chimpanzee they were studying, was capable of using sign language independently rather than simply mimicking human gestures. The Gardeners would have wanted to show that Washoe could use signs meaningfully in novel contexts without prior prompting or imitation to evidence true understanding and communication abilities. The specifics of their methods could include ensuring that Washoe's use of signs was spontaneous, appropriate to the context, and perhaps inventive, indicating a level of linguistic comprehension and cognitive ability beyond mere repetition.