Summarize research findings on language and cognition in animals.

In order to be considered language, communication must have meaningfulness, displacement, and productivity. By this definition, while animals may have signs (stereotyped communications about an animal's current state), they do not have language. Language is unique to humans. There is evidence that animals share some cognitive abilities with humans, from research showing that parrots can reason, dolphins understand the concepts of same and different, and some animals can pass the "mirror test' and show self-awareness.