Final answer:
Washoe the chimpanzee exhibited the use of protolanguage by combining signs to represent a swan, demonstrating an advanced level of cognitive ability similar to the early stages of human language development.
Step-by-step explanation:
When Washoe, a chimpanzee, combined the signs for water and bird to denote a swan that she saw, she was displaying a protolanguage ability. This type of communication shows the basic capacity to combine different signs to create new meanings, which is considered a step towards language development. In Washoe's case, the creation of a new sign by combining two known signs represents an elementary form of symbolization, which is akin to the building blocks of human language. Unlike other animal communication systems that are highly constrained, what Washoe demonstrated is a more open-ended use of signs that indicates a higher level of cognitive processing typically associated with the capability for language.